Hi Rob -- I did the original design of this engine and would like to see you get this overheating problem solved. The other thing I strongly recommend you do is to remove the big plug at the top of the block (the one that has the water pressure fitting in it). Iook down that hole and see if there's some debri just below there blocking the water from entering the passageway into the exhaust cover. Almost all the water from the pump has to flow up thru this hole and make the right angle bend into the exhaust cover.. A small amount of water does enter the block thru a small 1/4 inch hole drilled in the bottom of each bank. These are there to act as drains to empty the block on shutdown but they do help fill the block while running and can account for the small flow you're seeing thru your telltale as well as partial cooling for low speed running but are not near enough for normal speeds. Hope this helps!!
other than things i have talked about (55 years mechanic now) I saw you pull big impeller parts out. That plate where you did that comes off. That will give you access to the rest of the waterline from the pump to the block. Take it all apart friend. while apart hook your garden hose to the tube again from the bottom and turn it on high. See what shoots up into that mid section. If nothing or just a small amount there is still a blockage there. Do not put the power-head back on until you get this part free flowing, then fill the exit areas of the mid with water and see if it is draining. If not, the problem is in that same area. That stainless bolt going downwards right where you pulled the chunks out, take it out and split that area. You will see..... Also yes, pull the water-jacket covers on the heads and find diagrams of the entire water system. You are doing great. Just keep it up, there is not much left guys...
Hi Rob, I’m a bit of a NEWB myself when it comes to these Merc motors, but due to a couple recent overheat issues on two of my motors, I have become extremely familiar with the cooling systems. Here’s a couple additional troubleshooting options for you: 1) pull your water jackets on your 2 piece heads. In your previous videos, I noticed you yanked the heads but did not inspect water jackets for blockages. This is a common problem with two piece heads. 2) index your flywheels with TDC of each cylinder. With a paint marker, Write down the cylinder number on top of the flywheel. Run a timing light over the flywheel with the motor on muffs to diagnose if you have a double fire condition. All cylinders should fire within time. If they do not, you have a trigger, stator or coil issue. You can diagnose if this is a potential problem by using a thermal heat gun to check for abnormal heat on certain cylinders. For example: starboard is hot, but port is 15 degrees cooler or vice versa. Another example: cylinder 3 & 4 are hot, but 1, 2, 5, & 6 are 15 degrees cooler. This is almost a dead ringer for coil/carb problems. 3) is your poppet opening? A healthy/operational poppet is designed to cool the motor when at higher RPMS. In your case, higher rpms are where you begin to see an overheat condition. To test your poppet on muffs, look at your water PSI gauge. Hold the motor around 3 grand. You should see the water PSI start to climb with your RPMS, however there will be a noticeable drop in water pressure once your poppet opens. This is hot water previously passed through cylinders exiting through your poppet to your propeller and exhaust to adequately cool the motor at higher RPMS. if this is not happening, you need to determine why the poppet diaphragm is not opening. It could be due to lack of water pressure being fed to your poppet or it could be a defective diaphragm, spring, flapper, etc. I see that you replaced the poppet already, so I’d be guessing your problem is a lack of water pressure to the poppet. Thermostats are designed to cool your motor at idle, but poppet regulates temps at higher RPMs. 4) fuel also cools your motor at higher RPMS. Inspect your fuel pump and carbs for blockages causing a lean/hot motor. 5) enjoy a few more beers and hair loss diagnosing shit likes this. Cheers man. I hope this helps! -Tim
Hey Rob, the copper tube that carry’s the water from the water pump to the power head has rubber seals on both ends. One is in the water pump and the other is on the exhaust plate. I’ve seen those seals swell up and restrict water flow. Hope that helps.
Yes, I haven't even watched the video yet but I have seen a number of problems with the rubber seals at each end of the copper water tube leaking and so on..
@@davessparetime83 either the water that's being pumped isn't going out the block's cooling system drains OR the poppet valve isn't opening and relieving the excess pressure..
**guess pressure from the cylinders could be getting into the cooling system and causing the high pressure BUT I would think the poppet valve would still be able to relieve the pressure still.. V so I think only one of the 2 things could be causing This..
I feel your pain and frustration I have been there more then once with more then one boat I sincerely hope you find the issue and stick with it and not give up.
G’day With the engine off, have you tried connecting a hose to the inlet, and removing the thermostats (and leave the holes open), and checking if the water flows freely out the holes, if it does, you know the system is good till till it leaves the heads, if not, you must have a blockage or fault from the intake, if all good, you could then connect the hose to tubes after the thermostats, and see if there is a blockage in that part Keep the videos comming!
Hello from here in Maryland I had a Mercury Black Max 150 and he was overheating just like yours was took it to a dealer and they said it had to do with the stator for the charging system that also controls the timing and if that is off or goes too high it will overheat at mid to high RPMs but not at idle I would give it a try I hope this helps you out and your boat looks great
hey rob,check to make sure your popp it valve is open ing at plane off speed.got that same engine,had my popp it valve seat come out when valve was opening,there for not letting the block water out causing internal overtheating
Rob, I read someone else post on this and I went back ep #6. I found he was correct you didn't pull the outside chamber on the heads. He is correct in saying there may be some debris in there. In this post I suggested you get a repair manual and I still stick by that statement. Here is the thing I will help us help you better. Keep up the videos.
Hi Rob. Now you need to run that engine with the Poppit valve removed. The old F1 Race guys did not have thermostats and Poppit valves. Normally you remove the whole internal poppit valve assembly including the diaphragm, but re-assemble with the plates. You will end up leaking water out the tiny little vent hole. Close that up with a little self tapping screw and a gasket or O ring, then give it another run, take out the thermostats, as well
Rob, since there is no water coming out of the exhaust and I see water coming out of the visual check outlet obviously under too much pressure, this tells me there is a blockage between the check outlet and the exhaust. With a blockage there, the only water flow is what goes thru the check outlet. That is why it does ok at very low speeds. Check the water passage in that area and I will bet you will find something. Good luck. I want you to find it and start enjoying a great boat!
Just because you replaced existing gaskets with the same doesn't mean they are correct. Are you sure you have the right adapters on that mid for the correct water flow path? Can you witness the poppet opening by watching the WP gage? Have you checked each hole with a temp gun to try isolating the heat to a single or multiple holes? Have you checked for double fire?
Not a boat motor guy,but have a good bit of experience with air cooled 2strokes like saws,trimmers,blowers,mowers.Crank seals are notorious for causing overheating and often missed or overlooked by mechanics.Might be worth looking into.Good luck,keep up the great videos and content.
I'm wondering sent is only way it a full throttle I'm playing maybe the low unit is running out of water I got a 82 18ft fish and ski glastron kind of design after the James bonds boat it's more a speed boat but anyways it has 175 Johnson on it and it was doing the same thing around 55-65 I talked to the I bought it from which had it for day one drove straight to Austin Texas to get it and said few years back he we had the transom redone and it has started that he said off and on before then if you run hard all day out pulling a tube it get a little hot . Show I got hold of some people at glastron and the told me the proper sitting height for the motor on the transom and the listed speed the boat was supposed to do and come find out that deal ship he had bought it from had raised it inch and a half too hot when they set the motor on it and then the guy had raised it more to make it more try get more speed so I invested in a jet plate and have it a inch high then manufacturing which made a lot more stable but did lose five miles an hour on top in but gained it and take off I run an 18-in 21 pitch stainless steel prop and you can pull tubes all day long for Florida 5 seconds to 55
Crack in the cylinder wall? Compression in the cooling system from cylinder crack could increase water pressure. What about the pop-it valve being different?
The blown headgasket is very suspect, I'm no marine motor guy but I'd be finding why the gasket blew through the first time, and generally once they do you need to have the head machined.
Hi many thanks to you both for your boating content ! Just been watching ' 2.5L mercury overheating & torubleshooting' part 2 on 'You Tube , his motor is double sparking causing intake combustion mixture to be ignited and burned through the exhaust cycle. The video may be worth a look if not seen. Good Luck !
I thought i posted this in one of your last videos, but not for sure. With all you have done you need to check for a double fire in the cylinders. I was researching your problem and came a cross a similar issue another person had. He wound up ha ind double fire in the cylinders. The way he found it was with a timing light. He checked the timing mark and was gettting the light there. Then he went around the fly wheel and was getting a second location where the timing light was iluminating the timing mark on the flywheel.
Not sure if you figured out where water is leaking in but you should check your water pressure line. Especially where you spliced it. Only thing that makes sense to me why water is coming in that high.
Sit back, and look at the evidence. *Confirm the OB is REALLY overheating*. Confirm your water pressure gauge is correct. Try a different gauge. If all good there. Look again at the evidence again. High water pressure, I would interpret as a blockage. If you haven't done this, remove your thermostats, put them in a pan of water on the stove and boiling the water, confirm they open fully. Also make sure the water pump impeller is not installed backward. It could of been backward when YOU got the OB, and YOU just put it back together like it came out. This could possibly be giving you wrong readings on you water pressure gauge. Remove all water hoses, get a pressure washer run water thru all of them, do the same to the OB block. I love a good mystery, except when it comes to OBs, good luck!!
Do you have proper gauges and sensors? Wired properly? I mean is it actually over heating because when you checked with thermometer previously it wasn't hot. Also water won't really be coming out of the upper exhaust ports until the Tstat opens. If the tell tale is sending water and there's not too much back pressure on the exhaust through or around the prop you shouldn't see water from upper exhaust ports, when you run the boat up to temp then go to idle water should come from exhaust as the T stat is opened.
Cylinder heads clogged with lake debris? We had this happen on an old Evinrude outboard. Pulled the head and used draino to dissolve the organic matter plugging the water passages
check the bottom of the water pump base. I had hot exhaust water coming up through the o-ring seals. Only found it by pulling the drive apart multiple times.
I have recently bought 1981 Skeeter bass boat with 1981 Mercury Black Max V-150 and it was having this exact same problem. I ended up removing the cylinder heads, having them machined, replacing the thremostats, replacing the poppett valve, replacing the bottom and top kit of the water pump, etc. I got everything back together today and she runs bitchin on the hose and out of a water trough. I havent had it in the lake because.....when i was finsihing the motor I found a giant crack in the transom the the prior owner tried to fix (but didnt) and lied to me about it. Now i am doing a bunch of fiberglass repair I wasnt planning on. I havent been screwed in a long time but i sure got boned on this deal! Hope you find the problem with your boat!
What is your idle water pressure and what is your WOT pressure now? Also, what is the distance below the bottom of the boat for the water pickup? Is it possible the jack plate has the motor too high? Did you try lowering the jack plate to see if that causes any difference in temperature?
Hi mate Love the channel (s)! I have the same motor, same issues, done everything that you’ve done - pulling the power head Pull the housing under the impeller plate, mine was full of crap
Awesome idea! I am going to pull the powerhead again soon and try to figure out where those holes are... I didn't see any of them? Do you have a good reference photo?
Someone had commented (previous video) that it looked like steam coming out of the exhaust, meaning blown head gaskets. I didn't see anything steamy coming out this time, so perhaps that was part of the problem and it is now fixed? Perhaps Sara's suggestion that there is still some debris inside? Would it have been a good idea to fish some pipe cleaners through passages while it was apart, after blowing things out with compressed air, etc? Sometimes these things end up being something really small and stupid.
Just curious, did you use the cheaper paper gasket for the powerhead, or did you get the better coated gasket that is quite a bit thicker? When I have used the thinner paper gasket for the powerhead I have used either "Indian shellac" or some other gasket sealing stuff.. Just thinking out loud at the moment..
Also, if the engine block coolant drains are plugged, since this is a salt water motor if I remember correctly, so just figured I'd ask if you checked the block coolant drains when you had it apart?? That could be why not really getting water coming out of the mid section, and for the high pressure as well -- since I if the water can only leave through the telltale then that is going to make the pressure go up...
**is the pressure high even at idle?? Because these motors with this specific impeller are known for barely pumping enough water to make it pee out the telltale at idle..
Rob, run a drill bit thru the holes in the hull in case there's any silicone residue, counter sink the hole inside the hull & outside, fill with unwaxed gel-coat with milled fibers. The bevel on either side will lock in the repair to ensure water pressure/friction from working the repair loose
Shredded an impeller, that gets everywhere in the block, blocks water passages with ease. Reverse water flow with some pressure should blow the crap out.
Id try pre mixing your gas and just running it in the old school way. Turn off the oil injection. Richen up your fuel air mixture a hair and see if that helps.
Looking forward to an update on the Mercury 150. I have a 1995 mercury EFI having the same problems. I have done many of the things you done and so have the mechanics but no change in the water temp problems. I’ve taken it to 3 different marine mechanics spent big $ and still getting hot. Very frustrating to sat the least. You would think the mechanics would have figured it out. Hopefully you can figure it out and post soon.
You say the engine was over heating before you got it? You replaced the gaskets with exactly the same ones. The engine may have had the wrong gaskets to start with. Check every hole in the gasket with every hole in the block and in the heads to make sure it is the right gasket.
That's been suggested. Run until hot. Pull the kill switch and photo the plugs for someone to interoperate. Too lean and too advanced will burn up a motor. Plugs will tell.
I couldn’t tell with the Timelapse but it didn’t look like you had the cardboard/plastic sleeve that goes between the water pump and the pipe that goes up to the powerhead
OK on the block he took the heater to the power head off of the lower unit are the pistons are all scored scored on the block and that pick might cause you overheating problem also So you might have to rebuild your engine
Yes one cylinder burning up is all it takes. Because friction equals heat. He has done no cylinder temps or plug checks. Let alone compression or leak down.
I want to say say thank you for Merc Mondays I have learned a lot even even when I thought I knew almost everything about outboards In general You have one of the most down home TH-cam channels that is not super high dollar production ones That you see on here That you would think would learn everything And anything there is to know about outboards And mercuries I know you're probably at your wits end But I hope knowing that you are helping thousands of people people with their little problems I know you it can be so frustrating when you continue to have these little problems but I really am starting to think that there's a problem maybe in mid or lower unit or somewhere theres a crack in the cylinder heads which is letting exhaust escape Causing extreme high Water pressures But whatever you do don't replace that engine Completely,it is fixable Has to be cheaper than the price of these newer outwards which in my opinion are A 100% cheaper made And have more problems But I'm sure you already know that Just like with anything that was made in the eighties and nineties and even in the mid to in 2 thousands We're made with better materials and forget replacing parts on anything that is practically practically 5 too 10 years old they are crazy expensive. Just try to stay positive I mean how could you not look at all your toys and no one could ask for a cooler more Beautiful woman that don't don't go crazy when you want to bring home a new toy That needs a bunch of money thrown at it, No she gets right down to business and start tarring it part trying to fix it you are Lucky Man. Believe that.
You may have a good point If I understand what you were saying. Maybe he is not getting high water pressure and maybe somehow exhaust gasses from compression are pushing against the water that is supplied by the lower unit. When he starts to get higher rpms it really pushes against the cooling system.
I feel the frustration. I think we will be getting a cold snowy winter here in Wisconsin. All the acorns are a tell tale sign. That may be it for boating. Get the sleds fired up 😁
With the exhaust cover off look down the rectangular opening at the top of the block. this passageway lets water come thru from the pump into the exhaust cover and then goes into the block. The core that forms this passageway meets the core coming up from the bottom of the block. Where these two cores meet there's usually a thin wall of flash after casting which is supposed to be removed later. maybe it was not completely removed and is blocking most of the water from the pump.
not sure if you mention but that avenger looks like model 163 which is 16'7" rating plate say up to 125hp I've got one in my backyard it has a 140hp evinrude o/b
Have you changed the impeller? Is your leg the right height for the hull? Maybe when planing your water pickup is above water level? How is the tell tail when planing?
Keep watching this series. In the videos I replace the thermostats impeller poppet valve check that it’s fully submerged on plane and tell tale is fine.
There’s likely blockages In the block passages which will require tear down and tank dipping the block. But first try a softer poppet spring if you have one, that one you have may be too stiff, good luck guys!!!
Yes the poppet dumps excess water at speed. Looked like he hooked a garden hose up to the midsection intake and didn't defeat the spring. Didn't flow. Nothing out of the tell tale either.
I have the same exact motor, 87 150 XR2. Water pressure runs 5-10 at idle and 20+ at WOT. My temperagure gauge skyrockets at WOT every single time. These motors just run hotter than others. I just ignore my temp gauge. I don't think it's actually overheating considering I've ran it for a year without blowing up. Just my experience.
I have the same motor and same issue. My alarm doesn't go off but the temp gauge goes to 3/4 hot. The motor doesn't get as hot when there is less weight in the boat. I've run the boat at WOT long periods and it hasn't seized yet...
How come I don't hear a hot horn when you take off and when you shut it down and turn the key back on the horn should stay on motor doesn't cool down that fast water leak when you back in or after you start motor water pressure hose leaking
Hey guys, so bummed you are not able to get the bugs worked out yet on your Black Max. I don't Know if you ever got my responce to the email about my photos I shared by email. I just bought another cool vintage boat but it was a competitor of Mercury. Check out a 1964 OMC Deluxe, I have great plans maybe even swap out with a spare built 260 mercruiser I/O I have.
I had the same issue with a 1994 Evinrude 150. it was the automatic oiler. my boat has an alarm diagram. a long beeeeeeep is over heating, a beep, beep, beep is an oil issue. when i was at low RPM's no alarm ( 1000 to 2000 ). the reason was that the pump diaphragm had a crack in it and it only started sucking air when it was under high presser ( full throttle ) . i was going to change the automatic oiler but it was over $400 so i cut the oil alarm wires, capped off the auto oiler and pre-mixed the gas. NO more problems. my water pressure runs very high at high RPM. ( 36 to 40 ). hope this helps.
I do all my own work on my boat. I am HVAC certified as my job. My cars get fixed by me always. However to repair boats, airplanes etc. It is very expensive to do things right. All shortcuts are cheap. The real deal costs. Not a poor mans game.
Do you think the water pickuo ir completely submerged in waster at plane with the jackplate? I had the same engine on a checkmate, and the top two water intake holes were bloxked off, i never had an overheating problem.and i had the engine at the top of the jackplate
Hey Rob , love the channel! fellow Wisconsinite myself , where are you guys located? also with regards to the boat might be worth it to recheck that block for cracks and such even with a cracked block it will still run good. But that water oil mix didn’t look that great to me just my opinion hard to give good advice without actually looking at it
Try the original pressure relife valve spring looked shorter in the vid , , even chop the new pressure relife down until there is minimal pressure and retest . I think the relife valve is not opening at all .
If your water pressure sender/gauge are correct and you have super high pressure again I would say a head or two is "warped" and even though everything is fresh you are still leaking high pressure gasses into the cooling system.
When you 1st start to engine up I did not see no water coming out of the poor holes from the housing on the housing the war is post to come out soon the engines running but doesn't come but it doesn't come out it could be clogged and overheat it's supposed to be a big stream of water coming at the portholes so the injured runs
Now warm it up in the driveway and do a compression check. They should be around 120. FWIW, I almost bought a used boat from a DEALER with a 150 Merc that was the next generation after the BM. It also overheated constantly, and the mechanics tried everything in the book to fix it. They just gave up on it and were selling the boat as-is, with a free motor. You can’t fix everything.
Nope. I’ve found a lot of impeller chunks in the engine and tried forward and backward flushing it. New tstats poppit valve, new head gaskets, man I’m running out of ideas
"beep beep beep" is the low oil warning. steady "beeeeeep" is the overheat warning. before you do any more big expensive work, test the sensor in the starboard head to make sure it sends a steady beep when you heat it. if it works correctly, the head it's mounted in is not overheating.
Maybe the gages are bad and it's not over heating have same motor and when it overheated on me there a alarthat comes from throttle indicating over heating 🤷
Have you checked the water up pipe from the impeller to the powerhead? Maybe some pieces of old impeller stuck in it. Also it was hard to see but I didn’t see the pisser/telltale ?
Try deleting the poppet completely. Looking at one of your previous videos, your motor has a different style poppet than mine so I can’t give you the exact process which I did. However, it is a way to rule out a potential source of overheating. Also get rid of t-stats and run washers. 1/8th inch fender washers work perfect using the factory t-stat rubber seal, and provide enough restriction in the flow to cool properly. I was having similar issues in my 2.5 200, minus the crazy high water pressure, and those two things finally solved my overheating issues. It can be very frustrating but you will figure it out, Keep the videos coming!
Don't do any of this stuff for a stock motor!! The stock cooling system is absolutely perfect for keeping a stock motor cooled.. possibly if there was a bunch of modifications to the engine, and even then I have never had a problem with the stock factory cooling system...
**haven't watched the video yet BUT, if the motor is having really high water pressure then that almost for sure is a problem with the poppet valve as it's job is to relieve the water pressure when you are revving up..
As I'm watching the video, I can't help but wonder if a gasket is leaking, Like a head gasket OR the power head mounting gasket and exhaust is getting to the cooling system and causing the high water pressure, BUT, if that was the case I would think it would be happening at idle/off idle as well, not just on plane..
@@BabyCharlotteschannel like I said.. just a way to rule out a potential source of overheating as he already has replaced/ checked almost all common points of failure.
I see that temperature reads high as soon as boat gets on plane, but I didn't hear the constant beep alarm of over temperature. It should by deep when temperature of the engine is abnormally high. I understand that you can hear a short beep when you turn the key on. I remember that you had an intermittent beep when small oil enclosure is not full, a sign of no oil transfer from big oil tank. Seems like you already fixed that, I don't know how, but the important thing here is if temperature alarm beeps constantly when temperature needle goes up. Does your temperature alarm ever beep, or it does not? You can run your engine without the cover and use the laser thermometer to check actual temperature of each cylinder.
Yes no temperatures are being measured. The gauge works but shows no temp reading. The overheat alarm also not tested or calibrated. He could be chasing a ghost.
Try to talk to small town bassing channel he has rebuilt a few now and just had one that was overheating do to it double fireing he might can help you just checked it with a timing light in the dark just to rule that out before u tear it back apart
This motor has a two piece heads Pull the water jacket off the back of the head and have a peek. Will need new gaskets, but could be a blockage inside.
ok hook up water flush disconnect hoses and watch water flow from bottom to top, maybe pull tstats if you must for flow test. my suspicion is that popit valve. modify the old one by cutting the spring or something to cause it to be open. then see if you get water out exhaust at prop. I didn't know the water wasn't coming through ex that is your problem. when you fix that it will be fixed, I think it's a issue with that weird ass part, never seen one on a johnson or a rude
Hi Rob -- I did the original design of this engine and would like to see you get this overheating problem solved. The other thing I strongly recommend you do is to remove the big plug at the top of the block (the one that has the water pressure fitting in it). Iook down that hole and see if there's some debri just below there blocking the water from entering the passageway into the exhaust cover. Almost all the water from the pump has to flow up thru this hole and make the right angle bend into the exhaust cover.. A small amount of water does enter the block thru a small 1/4 inch hole drilled in the bottom of each bank. These are there to act as drains to empty the block on shutdown but they do help fill the block while running and can account for the small flow you're seeing thru your telltale as well as partial cooling for low speed running but are not near enough for normal speeds. Hope this helps!!
Hey mate , big fan of your engine and thanks 🙏 they're so fun to play with here in Australia 🦘👍
other than things i have talked about (55 years mechanic now) I saw you pull big impeller parts out. That plate where you did that comes off. That will give you access to the rest of the waterline from the pump to the block. Take it all apart friend. while apart hook your garden hose to the tube again from the bottom and turn it on high. See what shoots up into that mid section. If nothing or just a small amount there is still a blockage there. Do not put the power-head back on until you get this part free flowing, then fill the exit areas of the mid with water and see if it is draining. If not, the problem is in that same area. That stainless bolt going downwards right where you pulled the chunks out, take it out and split that area. You will see..... Also yes, pull the water-jacket covers on the heads and find diagrams of the entire water system. You are doing great. Just keep it up, there is not much left guys...
Have you actually put a laser thermometer on the engine while on the water to see what the temp is getting too?
Yes they did
Agreed
Hi Rob,
I’m a bit of a NEWB myself when it comes to these Merc motors, but due to a couple recent overheat issues on two of my motors, I have become extremely familiar with the cooling systems. Here’s a couple additional troubleshooting options for you:
1) pull your water jackets on your 2 piece heads. In your previous videos, I noticed you yanked the heads but did not inspect water jackets for blockages. This is a common problem with two piece heads.
2) index your flywheels with TDC of each cylinder. With a paint marker, Write down the cylinder number on top of the flywheel. Run a timing light over the flywheel with the motor on muffs to diagnose if you have a double fire condition. All cylinders should fire within time. If they do not, you have a trigger, stator or coil issue. You can diagnose if this is a potential problem by using a thermal heat gun to check for abnormal heat on certain cylinders. For example: starboard is hot, but port is 15 degrees cooler or vice versa. Another example: cylinder 3 & 4 are hot, but 1, 2, 5, & 6 are 15 degrees cooler. This is almost a dead ringer for coil/carb problems.
3) is your poppet opening? A healthy/operational poppet is designed to cool the motor when at higher RPMS. In your case, higher rpms are where you begin to see an overheat condition. To test your poppet on muffs, look at your water PSI gauge. Hold the motor around 3 grand. You should see the water PSI start to climb with your RPMS, however there will be a noticeable drop in water pressure once your poppet opens. This is hot water previously passed through cylinders exiting through your poppet to your propeller and exhaust to adequately cool the motor at higher RPMS. if this is not happening, you need to determine why the poppet diaphragm is not opening. It could be due to lack of water pressure being fed to your poppet or it could be a defective diaphragm, spring, flapper, etc. I see that you replaced the poppet already, so I’d be guessing your problem is a lack of water pressure to the poppet. Thermostats are designed to cool your motor at idle, but poppet regulates temps at higher RPMs.
4) fuel also cools your motor at higher RPMS. Inspect your fuel pump and carbs for blockages causing a lean/hot motor.
5) enjoy a few more beers and hair loss diagnosing shit likes this.
Cheers man. I hope this helps!
-Tim
Hey Rob, the copper tube that carry’s the water from the water pump to the power head has rubber seals on both ends. One is in the water pump and the other is on the exhaust plate. I’ve seen those seals swell up and restrict water flow. Hope that helps.
Yes, I haven't even watched the video yet but I have seen a number of problems with the rubber seals at each end of the copper water tube leaking and so on..
If so then why the high water pressure?
@@davessparetime83 either the water that's being pumped isn't going out the block's cooling system drains OR the poppet valve isn't opening and relieving the excess pressure..
**guess pressure from the cylinders could be getting into the cooling system and causing the high pressure BUT I would think the poppet valve would still be able to relieve the pressure still..
V so I think only one of the 2 things could be causing This..
@@davessparetime83 because the tube that goes to a speedo or water pressure gauge is below those rubber grommets.
I feel your pain and frustration I have been there more then once with more then one boat I sincerely hope you find the issue and stick with it and not give up.
I have really enjoyed watching this series. I hate it is still giving you issues. Keep making the videos.
G’day
With the engine off, have you tried connecting a hose to the inlet, and removing the thermostats (and leave the holes open), and checking if the water flows freely out the holes, if it does, you know the system is good till till it leaves the heads, if not, you must have a blockage or fault from the intake, if all good, you could then connect the hose to tubes after the thermostats, and see if there is a blockage in that part
Keep the videos comming!
th-cam.com/video/8S4I9UmSxcM/w-d-xo.html
Hello from here in Maryland I had a Mercury Black Max 150 and he was overheating just like yours was took it to a dealer and they said it had to do with the stator for the charging system that also controls the timing and if that is off or goes too high it will overheat at mid to high RPMs but not at idle I would give it a try I hope this helps you out and your boat looks great
hey rob,check to make sure your popp it valve is open ing at plane off speed.got that same engine,had my popp it valve seat come out when valve was opening,there for not letting the block water out causing internal overtheating
poppi it valve operates by block water pressure
Rob, I read someone else post on this and I went back ep #6. I found he was correct you didn't pull the outside chamber on the heads. He is correct in saying there may be some debris in there. In this post I suggested you get a repair manual and I still stick by that statement. Here is the thing I will help us help you better. Keep up the videos.
Definitely going to pull that outside chamber when i get back to it, but trying to get the SST going....
Did you check the head with a straight edge to make sure it’s not warped
Hi Rob. Now you need to run that engine with the Poppit valve removed. The old F1 Race guys did not have thermostats and Poppit valves. Normally you remove the whole internal poppit valve assembly including the diaphragm, but re-assemble with the plates. You will end up leaking water out the tiny little vent hole. Close that up with a little self tapping screw and a gasket or O ring, then give it another run, take out the thermostats, as well
Great idea, I am going to try this next!
Rob, since there is no water coming out of the exhaust and I see water coming out of the visual check outlet obviously under too much pressure, this tells me there is a blockage between the check outlet and the exhaust. With a blockage there, the only water flow is what goes thru the check outlet. That is why it does ok at very low speeds. Check the water passage in that area and I will bet you will find something. Good luck. I want you to find it and start enjoying a great boat!
Also, rising water pressure is slightly concerning because you’re more interested in volume flow and higher pressure means lower volume flow typically
Just because you replaced existing gaskets with the same doesn't mean they are correct. Are you sure you have the right adapters on that mid for the correct water flow path? Can you witness the poppet opening by watching the WP gage? Have you checked each hole with a temp gun to try isolating the heat to a single or multiple holes? Have you checked for double fire?
Not a boat motor guy,but have a good bit of experience with air cooled 2strokes like saws,trimmers,blowers,mowers.Crank seals are notorious for causing overheating and often missed or overlooked by mechanics.Might be worth looking into.Good luck,keep up the great videos and content.
That is because crank seals on air cooled 2strokes is a air leak and causes lean condition
I'm wondering sent is only way it a full throttle I'm playing maybe the low unit is running out of water I got a 82 18ft fish and ski glastron kind of design after the James bonds boat it's more a speed boat but anyways it has 175 Johnson on it and it was doing the same thing around 55-65 I talked to the I bought it from which had it for day one drove straight to Austin Texas to get it and said few years back he we had the transom redone and it has started that he said off and on before then if you run hard all day out pulling a tube it get a little hot . Show I got hold of some people at glastron and the told me the proper sitting height for the motor on the transom and the listed speed the boat was supposed to do and come find out that deal ship he had bought it from had raised it inch and a half too hot when they set the motor on it and then the guy had raised it more to make it more try get more speed so I invested in a jet plate and have it a inch high then manufacturing which made a lot more stable but did lose five miles an hour on top in but gained it and take off I run an 18-in 21 pitch stainless steel prop and you can pull tubes all day long for Florida 5 seconds to 55
And you may want to check your prop too I know can eject away the lower unit pulls water in
Crack in the cylinder wall? Compression in the cooling system from cylinder crack could increase water pressure. What about the pop-it valve being different?
The blown headgasket is very suspect, I'm no marine motor guy but I'd be finding why the gasket blew through the first time, and generally once they do you need to have the head machined.
I had the same trouble with a sled. Turned out to be timing. Is there a possibility it's out of time?
Hi many thanks to you both for your boating content ! Just been watching ' 2.5L mercury overheating & torubleshooting' part 2 on 'You Tube , his motor is double sparking causing intake combustion mixture to be ignited and burned through the exhaust cycle. The video may be worth a look if not seen. Good Luck !
I thought i posted this in one of your last videos, but not for sure. With all you have done you need to check for a double fire in the cylinders. I was researching your problem and came a cross a similar issue another person had. He wound up ha ind double fire in the cylinders. The way he found it was with a timing light. He checked the timing mark and was gettting the light there. Then he went around the fly wheel and was getting a second location where the timing light was iluminating the timing mark on the flywheel.
Not sure if you figured out where water is leaking in but you should check your water pressure line. Especially where you spliced it. Only thing that makes sense to me why water is coming in that high.
That is 100% it. lol. Oops.
Sit back, and look at the evidence. *Confirm the OB is REALLY overheating*. Confirm your water pressure gauge is correct. Try a different gauge.
If all good there. Look again at the evidence again. High water pressure, I would interpret as a blockage.
If you haven't done this, remove your thermostats, put them in a pan of water on the stove and boiling the water, confirm they open fully.
Also make sure the water pump impeller is not installed backward. It could of been backward when YOU
got the OB, and YOU just put it back together like it came out. This could possibly be giving you wrong readings on you water pressure gauge.
Remove all water hoses, get a pressure washer run water thru all of them, do the same to the OB block.
I love a good mystery, except when it comes to OBs, good luck!!
Do you have proper gauges and sensors? Wired properly? I mean is it actually over heating because when you checked with thermometer previously it wasn't hot. Also water won't really be coming out of the upper exhaust ports until the Tstat opens. If the tell tale is sending water and there's not too much back pressure on the exhaust through or around the prop you shouldn't see water from upper exhaust ports, when you run the boat up to temp then go to idle water should come from exhaust as the T stat is opened.
Cylinder heads clogged with lake debris? We had this happen on an old Evinrude outboard. Pulled the head and used draino to dissolve the organic matter plugging the water passages
Glad you took my advice on doing the head gaskets and cleaning the water ports . Its cheap insurance at least now you know you got it covered
check the bottom of the water pump base. I had hot exhaust water coming up through the o-ring seals. Only found it by pulling the drive apart multiple times.
I have recently bought 1981 Skeeter bass boat with 1981 Mercury Black Max V-150 and it was having this exact same problem. I ended up removing the cylinder heads, having them machined, replacing the thremostats, replacing the poppett valve, replacing the bottom and top kit of the water pump, etc. I got everything back together today and she runs bitchin on the hose and out of a water trough. I havent had it in the lake because.....when i was finsihing the motor I found a giant crack in the transom the the prior owner tried to fix (but didnt) and lied to me about it. Now i am doing a bunch of fiberglass repair I wasnt planning on. I havent been screwed in a long time but i sure got boned on this deal! Hope you find the problem with your boat!
What is your idle water pressure and what is your WOT pressure now? Also, what is the distance below the bottom of the boat for the water pickup? Is it possible the jack plate has the motor too high? Did you try lowering the jack plate to see if that causes any difference in temperature?
That would cause low pressure not high though.
I've covered this in previous episodes... the entire lower unit is submerged and right now the entire engine hangs too low to go very fast.
Check discharge hoses from thermostats to mid section as I had a blockage in mine
Cracked cylinder sleeve?
Did you check the heads, block for straightness?
Hope you get it sorted. Just ordered some of the Klasse you rated and looking forwards seeing the results.
Hi mate
Love the channel (s)!
I have the same motor, same issues, done everything that you’ve done - pulling the power head
Pull the housing under the impeller plate, mine was full of crap
I have a flow chart of the cooling system I can send to you. What’s the easy way todo that.
Rob, The exhaust plate holes (18 of them i believe) become clogged, Did you clean that when you removed the plate? Most people redrill with 3/8s bit
Awesome idea! I am going to pull the powerhead again soon and try to figure out where those holes are... I didn't see any of them? Do you have a good reference photo?
Those are 2 piece heads. Did you pull the plates off of the heads and look around?
Did you have a look at Small Town Bassin here on TH-cam. You need to check your timing for a cylinder double spark. That can be the culprit.
water passages are clogged with the broken off water pump impeller blades.. Do you recall the old impeller missing a lot blades?
Someone had commented (previous video) that it looked like steam coming out of the exhaust, meaning blown head gaskets. I didn't see anything steamy coming out this time, so perhaps that was part of the problem and it is now fixed?
Perhaps Sara's suggestion that there is still some debris inside? Would it have been a good idea to fish some pipe cleaners through passages while it was apart, after blowing things out with compressed air, etc?
Sometimes these things end up being something really small and stupid.
Have you looked for lean condition or check the timing
Have you checked the timing and electrical system. A faluty coil or switch box can cause this issue as well
Just curious, did you use the cheaper paper gasket for the powerhead, or did you get the better coated gasket that is quite a bit thicker?
When I have used the thinner paper gasket for the powerhead I have used either "Indian shellac" or some other gasket sealing stuff..
Just thinking out loud at the moment..
Also, if the engine block coolant drains are plugged, since this is a salt water motor if I remember correctly, so just figured I'd ask if you checked the block coolant drains when you had it apart??
That could be why not really getting water coming out of the mid section, and for the high pressure as well -- since I if the water can only leave through the telltale then that is going to make the pressure go up...
**is the pressure high even at idle??
Because these motors with this specific impeller are known for barely pumping enough water to make it pee out the telltale at idle..
Rob, run a drill bit thru the holes in the hull in case there's any silicone residue, counter sink the hole inside the hull & outside, fill with unwaxed gel-coat with milled fibers.
The bevel on either side will lock in the repair to ensure water pressure/friction from working the repair loose
Shredded an impeller, that gets everywhere in the block, blocks water passages with ease. Reverse water flow with some pressure should blow the crap out.
Id try pre mixing your gas and just running it in the old school way. Turn off the oil injection. Richen up your fuel air mixture a hair and see if that helps.
Replaced the whole poppet valve or just the gaskets? The spring also wears out.
Looking forward to an update on the Mercury 150. I have a 1995 mercury EFI having the same problems. I have done many of the things you done and so have the mechanics but no change in the water temp problems. I’ve taken it to 3 different marine mechanics spent big $ and still getting hot. Very frustrating to sat the least. You would think the mechanics would have figured it out. Hopefully you can figure it out and post soon.
Did you clean the water jackets ?
You say the engine was over heating before you got it? You replaced the gaskets with exactly the same ones. The engine may have had the wrong gaskets to start with. Check every hole in the gasket with every hole in the block and in the heads to make sure it is the right gasket.
What do your plugs look like? I’ve had motors run hot because they’re running lean due to carbs needing cleaning/rebuild.
That's been suggested. Run until hot. Pull the kill switch and photo the plugs for someone to interoperate. Too lean and too advanced will burn up a motor. Plugs will tell.
I couldn’t tell with the Timelapse but it didn’t look like you had the cardboard/plastic sleeve that goes between the water pump and the pipe that goes up to the powerhead
OK on the block he took the heater to the power head off of the lower unit are the pistons are all scored scored on the block and that pick might cause you overheating problem also So you might have to rebuild your engine
Yes one cylinder burning up is all it takes. Because friction equals heat. He has done no cylinder temps or plug checks. Let alone compression or leak down.
I want to say say thank you for Merc Mondays I have learned a lot even even when I thought I knew almost everything about outboards In general You have one of the most down home TH-cam channels that is not super high dollar production ones That you see on here That you would think would learn everything And anything there is to know about outboards And mercuries I know you're probably at your wits end But I hope knowing that you are helping thousands of people people with their little problems I know you it can be so frustrating when you continue to have these little problems but I really am starting to think that there's a problem maybe in mid or lower unit or somewhere theres a crack in the cylinder heads which is letting exhaust escape Causing extreme high Water pressures But whatever you do don't replace that engine Completely,it is fixable Has to be cheaper than the price of these newer outwards which in my opinion are A 100% cheaper made And have more problems But I'm sure you already know that Just like with anything that was made in the eighties and nineties and even in the mid to in 2 thousands We're made with better materials and forget replacing parts on anything that is practically practically 5 too 10 years old they are crazy expensive. Just try to stay positive I mean how could you not look at all your toys and no one could ask for a cooler more Beautiful woman that don't don't go crazy when you want to bring home a new toy That needs a bunch of money thrown at it, No she gets right down to business and start tarring it part trying to fix it you are Lucky Man. Believe that.
You may have a good point If I understand what you were saying. Maybe he is not getting high water pressure and maybe somehow exhaust gasses from compression are pushing against the water that is supplied by the lower unit. When he starts to get higher rpms it really pushes against the cooling system.
@@ES-xc6fk Yes compression and leakdown test.
I feel the frustration. I think we will be getting a cold snowy winter here in Wisconsin. All the acorns are a tell tale sign. That may be it for boating. Get the sleds fired up 😁
I hope so!
I think that you really need to figure out the high water pressure (water restriction) and you will also fix the overheating.
With the exhaust cover off look down the rectangular opening at the top of the block. this passageway lets water come thru from the pump into the exhaust cover and then goes into the block. The core that forms this passageway meets the core coming up from the bottom of the block. Where these two cores meet there's usually a thin wall of flash after casting which is supposed to be removed later. maybe it was not completely removed and is blocking most of the water from the pump.
not sure if you mention but that avenger looks like model 163 which is 16'7" rating plate say up to 125hp I've got one in my backyard it has a 140hp evinrude o/b
Have you changed the impeller? Is your leg the right height for the hull? Maybe when planing your water pickup is above water level? How is the tell tail when planing?
Keep watching this series. In the videos I replace the thermostats impeller poppet valve check that it’s fully submerged on plane and tell tale is fine.
There’s likely blockages In the block passages which will require tear down and tank dipping the block.
But first try a softer poppet spring if you have one, that one you have may be too stiff, good luck guys!!!
Yes the poppet dumps excess water at speed. Looked like he hooked a garden hose up to the midsection intake and didn't defeat the spring. Didn't flow. Nothing out of the tell tale either.
I have the same exact motor, 87 150 XR2. Water pressure runs 5-10 at idle and 20+ at WOT. My temperagure gauge skyrockets at WOT every single time. These motors just run hotter than others. I just ignore my temp gauge. I don't think it's actually overheating considering I've ran it for a year without blowing up. Just my experience.
Idk man I don't want to find out....
I have the same motor and same issue. My alarm doesn't go off but the temp gauge goes to 3/4 hot. The motor doesn't get as hot when there is less weight in the boat. I've run the boat at WOT long periods and it hasn't seized yet...
How come I don't hear a hot horn when you take off and when you shut it down and turn the key back on the horn should stay on motor doesn't cool down that fast water leak when you back in or after you start motor water pressure hose leaking
Hey guys, so bummed you are not able to get the bugs worked out yet on your Black Max. I don't Know if you ever got my responce to the email about my photos I shared by email. I just bought another cool vintage boat but it was a competitor of Mercury. Check out a 1964 OMC Deluxe, I have great plans maybe even swap out with a spare built 260 mercruiser I/O I have.
I was thinking, maybe the sender and temp guage combo are mismatched?
I had the same issue with a 1994 Evinrude 150. it was the automatic oiler. my boat has an alarm diagram. a long beeeeeeep is over heating, a beep, beep, beep is an oil issue. when i was at low RPM's no alarm ( 1000 to 2000 ). the reason was that the pump diaphragm had a crack in it and it only started sucking air when it was under high presser ( full throttle ) . i was going to change the automatic oiler but it was over $400 so i cut the oil alarm wires, capped off the auto oiler and pre-mixed the gas. NO more problems. my water pressure runs very high at high RPM. ( 36 to 40 ). hope this helps.
Is the water pickup coming out of the water when you plane out? It might be not getting enough water
No watch episode 3 we check it and it’s completely submerged
The definition of BOAT........Bust. Out. Another Thousand. I own a 1977 Mirro with a Merc Tower of Power. Love the old boats
That definition is repeated by people that can't work on things. I think I'm maybe $650 into this thing, so far.
I do all my own work on my boat. I am HVAC certified as my job. My cars get fixed by me always. However to repair boats, airplanes etc. It is very expensive to do things right. All shortcuts are cheap. The real deal costs. Not a poor mans game.
@@JeepisJunk I'm going to hit 60+ for under $1000, I know it. Stay tuned!
Do you think the water pickuo ir completely submerged in waster at plane with the jackplate? I had the same engine on a checkmate, and the top two water intake holes were bloxked off, i never had an overheating problem.and i had the engine at the top of the jackplate
Yes, it's completely 100 submerged. Keep watching, I show video of it buried. It's way submerged.
Hey Rob , love the channel! fellow Wisconsinite myself , where are you guys located? also with regards to the boat might be worth it to recheck that block for cracks and such even with a cracked block it will still run good. But that water oil mix didn’t look that great to me just my opinion hard to give good advice without actually looking at it
Could be a slight timing issue
My uncle had a xr4 that did them same things! And replace the lower unit and problem went away!
Try the original pressure relife valve spring looked shorter in the vid , , even chop the new pressure relife down until there is minimal pressure and retest . I think the relife valve is not opening at all .
Oh man, I don't know if I still have it. I will look around.
Have u done the impeller
If your water pressure sender/gauge are correct and you have super high pressure again I would say a head or two is "warped" and even though everything is fresh you are still leaking high pressure gasses into the cooling system.
When you 1st start to engine up I did not see no water coming out of the poor holes from the housing on the housing the war is post to come out soon the engines running but doesn't come but it doesn't come out it could be clogged and overheat it's supposed to be a big stream of water coming at the portholes so the injured runs
I had issues w my motor overheating supposibly as well but i solved it somehow as well. I still love this boat
Now warm it up in the driveway and do a compression check. They should be around 120. FWIW, I almost bought a used boat from a DEALER with a 150 Merc that was the next generation after the BM. It also overheated constantly, and the mechanics tried everything in the book to fix it. They just gave up on it and were selling the boat as-is, with a free motor. You can’t fix everything.
Lots of hard work 💦 New gages & Sensors ?
Possibly a part of a impeller hung up in it. Did you ever get it figured out?
Nope. I’ve found a lot of impeller chunks in the engine and tried forward and backward flushing it. New tstats poppit valve, new head gaskets, man I’m running out of ideas
@@ADDvanced I'll get back with you shortly, let me ask my unc a few questions about it. He's a Merc guru.
Just a thought. Could it be because of a double spark on one cylinder. Turn out the lights and watch with timing light. Maybe the problem.
Small town bassin has a video you need to watch
Sarah video! Love those sunglasses Rob.
Even if you get a rebuilt power head this thing is still a steal
Cut a loop off of the popet valve spring...
Thermal couple each spark plug and see what the temperatures are
"beep beep beep" is the low oil warning. steady "beeeeeep" is the overheat warning. before you do any more big expensive work, test the sensor in the starboard head to make sure it sends a steady beep when you heat it. if it works correctly, the head it's mounted in is not overheating.
Great advice! Thank you!
@@ADDvanced great video series. I’m on the edge of my seat to see the resolution so keep it up 👍
Maybe the gages are bad and it's not over heating have same motor and when it overheated on me there a alarthat comes from throttle indicating over heating 🤷
AWESOME... You got November temp... TUNE IN IT. I'd make sure the thermostat passages are flowing 100 % .
🇺🇸👍📹👀✌🍻🇺🇸
Love the colors, should have a 200 Merc...
I have on in the garage! :P
Have you checked the water up pipe from the impeller to the powerhead? Maybe some pieces of old impeller stuck in it. Also it was hard to see but I didn’t see the pisser/telltale ?
Yes it is clear
Try flushing the motor with Rydlyme. There are many videos on TH-cam detailing the procedure. Rydlyme may dissolve a blockage if there is one.
Try deleting the poppet completely. Looking at one of your previous videos, your motor has a different style poppet than mine so I can’t give you the exact process which I did. However, it is a way to rule out a potential source of overheating. Also get rid of t-stats and run washers. 1/8th inch fender washers work perfect using the factory t-stat rubber seal, and provide enough restriction in the flow to cool properly. I was having similar issues in my 2.5 200, minus the crazy high water pressure, and those two things finally solved my overheating issues. It can be very frustrating but you will figure it out, Keep the videos coming!
Don't do any of this stuff for a stock motor!!
The stock cooling system is absolutely perfect for keeping a stock motor cooled.. possibly if there was a bunch of modifications to the engine, and even then I have never had a problem with the stock factory cooling system...
**haven't watched the video yet BUT, if the motor is having really high water pressure then that almost for sure is a problem with the poppet valve as it's job is to relieve the water pressure when you are revving up..
As I'm watching the video, I can't help but wonder if a gasket is leaking, Like a head gasket OR the power head mounting gasket and exhaust is getting to the cooling system and causing the high water pressure, BUT, if that was the case I would think it would be happening at idle/off idle as well, not just on plane..
@@BabyCharlotteschannel like I said.. just a way to rule out a potential source of overheating as he already has replaced/ checked almost all common points of failure.
@@BabyCharlotteschannel he replaced head gaskets and powerhead base gasket
Most water tubes from the foot have a rubber grommet I bet the old one is stuck in the bottom of the motor or a piece of it is in the block
I see that temperature reads high as soon as boat gets on plane, but I didn't hear the constant beep alarm of over temperature. It should by deep when temperature of the engine is abnormally high.
I understand that you can hear a short beep when you turn the key on. I remember that you had an intermittent beep when small oil enclosure is not full, a sign of no oil transfer from big oil tank. Seems like you already fixed that, I don't know how, but the important thing here is if temperature alarm beeps constantly when temperature needle goes up.
Does your temperature alarm ever beep, or it does not?
You can run your engine without the cover and use the laser thermometer to check actual temperature of each cylinder.
Could it be the gauges are not functioning properly and the engine is not really overheating?
See last episode
@@ADDvanced I've seen all the episodes but I just don't remember everything since you've done so much already......Good luck
Yes no temperatures are being measured. The gauge works but shows no temp reading. The overheat alarm also not tested or calibrated. He could be chasing a ghost.
Sorry about the problems. Now the blue Sleekcraft PLEASE!!!
Have you seen small town bassen his video he had over heat issues
Try to talk to small town bassing channel he has rebuilt a few now and just had one that was overheating do to it double fireing he might can help you just checked it with a timing light in the dark just to rule that out before u tear it back apart
Timing as well as air/fuel mix (a plug read). Oil injection needs to go too. Not enough oil and that motor will run hot AF.
Are you sure your gauges are reading correctly.
The leak on the carpet could be coming from one of the water lines running to the gauges.
That is 100% it.
This motor has a two piece heads Pull the water jacket off the back of the head and have a peek. Will need new gaskets, but could be a blockage inside.
Good idea!
I was thinking the same but if air went through it then it might get hot but not that quickly.
ok hook up water flush disconnect hoses and watch water flow from bottom to top, maybe pull tstats if you must for flow test. my suspicion is that popit valve. modify the old one by cutting the spring or something to cause it to be open. then see if you get water out exhaust at prop. I didn't know the water wasn't coming through ex that is your problem. when you fix that it will be fixed, I think it's a issue with that weird ass part, never seen one on a johnson or a rude