Replacing Water Pump Impeller in Mercruiser Alpha 1 Stern Drive - 250 HP 4.5 Liter V6
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- เผยแพร่เมื่อ 5 พ.ย. 2022
- It's time to inspect and replace the water pump impeller in my Mercruiser Alpha 1 Gen 2 stern drive. This is in a 2018 Chaparral with a 250 HP 4.5 liter V6. I am using a Mercury impeller replacement kit part number 47-8M0100526 that includes the impeller, gaskets and seals to complete the job. I must remove the lower unit or lower gear case, disassemble the water pump to remove the impeller, reassemble and reinstall the lower unit.
NOTE: THIS VIDEO IS AN UPDATE TO A PREVIOUS ONE TO CORRECT AN ERROR IN REASSEMBLY PROCESS
I must be careful regarding safety because the parts are heavy and the water pump is critical to operation. If the pump does not operate correctly, the engine can overheat and be damaged and leave the boat stranded.
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Just one comment. I do enjoy that you leave nothing out of the details. One issue that I saw with the way that the manual advised to place the cover on by rotating the shaft. At 27:08 into the video watch what happens to the seal that is on the top gasket of the metal plate. The impeller catches it and rolls it into the housing.
Good catch, I hadn't seen that before. I think that the gasket has a soft bead on top that is molded as part of the gasket and it looks like the gasket was being pushed out of position and folded. It should have been ok, because the gasket straightened out and the holes were lined up when I finished. BUT, perhaps it would be better to have locating pins on all 4 corners to keep that from happening.
Great job. You had me laughing as I have done that more than once and that final alignment will cause some spicey language for sure. The water tube seals should get a good serving of grease as well. That's a great hobby you have!
You are correct on the grease. I did grease the o rings, I don't recall if I showed that.
Great video. I saw that water tube hit the dirt when you removed the lower unit. I thought, wonder if he saw that!
Yes, I missed it. And I've done this job enough times that I know better. But I have learned that making video while working causes a certain level of distraction and I need to be extra careful not to miss something routine.
I would pump the oil in from the bottom until it came out the vent hole, then cap that and continue to pump until reservoir is full at the engine.
Yes, that should certainly work. I have just taken to filling the bottle part way and by the time I pump oil in from the bottom, the monitor bottle has fed to the chamber with the vent plug and it just keeps running out. Then I just finish filling the monitor bottle.
What was the reason for changing the water pump? Was it a performance issue? Or just routine maintenance? I have a 2019 Searay with the 4.5L and I’m wondering if I need to check that now.
It is routine maintenance and I was feeling that it was due. Mercury recommends in the manual to inspect every year to be sure that the pump is in good condition. The challenge is that once you pull it all the way down, you might as well replace it, but it isn't required. In the older drives (early 90's? and before), it was recommended to always REPLACE annually. Then they redesigned to what was called the "floppy vane" pump impeller that has longer vanes. This newer pump impeller lasts much longer. I will admit that I do not inspect every year. This is the first time on my 2018. I cannot recommend this, but for a data point: On my 1998, I actually ran 10 years once without inspecting, and when I did it still looked rather good. But, I was only running about 15-20 hours per year, water was clean, I didn't stir up silt, and my lake was only about a mile long. I am very careful not to crank the engine dry. I watch engine temp carefully and if it would have started running warm, I wasn't far from home. On the other hand, I also destroyed one in less than 2 minutes when I forgot to turn the hose back on after an oil change. The best practice is to follow the book, but I have seen even Mercury has some comments about applying judgement based on your usage and experience.
Thanks for the info. I think I will put that on my Spring to-do-list before hitting the water as I have not inspected it yet and it’s a few years old. Thank you.