Speed Test Johnson 9.9

This video shows the speeds attainable with a 1976 Johnson 9.9 hp motor on my 12' jonboat. The actual net hp for this motor is about 8.3. I hope to later modify this motor with a 15 hp carburetor and a "tuned" 15 hp exhaust to increase the horsepower and then retest. The results of the carb change only are listed at the end of the video.

[@LCA1678]

You're awesome! Thank you for posting this, think you answered the "million dollar question," for many 9.9hp outboard owners!

[@carsten6823]

Thanks very much for these important information after and before tuning. I buyed a 9.9 Johnson for my 3. 20m inflatable boot and after this video i think it's enough

[@chadwassink7846]

Glad it helped.

[@darrenprebble6921]

dog was bit sad you forgot to take him/her 2nd time lol

[@chrisalbert3458]

Great Video- thank for doing it!

[@manko330]

great job doing testing,i have the same boat with a Yamaha 2.5 hp 4-stroke. top speed is 6 mph. the boat will not plane.

[@mosesbullrush8051]

The narrow jon boat (36) slow down more with added weight. The wider jon boats (48) are less affected by added weight.

[@nitroevaderbx]

Thanks for the very informative video, I want one.

[@mrwilliamdmoss]

Thanks for posting, very informative.

[@joeybrioso9408]

Where can I find a 15hp carburetor for my 9.9 Johnson 1976? It’s impossible

[@26dredarkk]

Im looking myself lol

[@kidddogbites]

Scour ebay for months at a time

[@kavak1344]

Did you ever modify it, update? Thinking of doing this with mine

[@edcrouse8294]

I live in Tampa and back when I had my boat which was a 1959 DuraCraft the jet skiers clock me at 33 knots with my dog that weighs 65 pounds inside but I also had a concrete block in the front a standard 8 inch by 12 inch

[@richcarolan5696]

Hi jus got lowes jon with a 6hp was the trick to get on plane or nose down mine jus rides a wheelie n get no speed no power trim n set on lowest setting down

[@FergusScotchman]

Dont need much more than that, my friend!

[@chadwassink7846]

The 9.9 is gross horsepower at the flywheel. The net horsepower at the propeller is closer to 8.3 from what I've read. There are some losses getting that power to the prop.

[@micracer99]

What size prop and pitch!

[@goodbuddysguns506]

Can you do an up river boat test?

[@POOHBEAR2170]

nice vid

[@thebigmann25]

Why is it actually a 8.3 hp?

[@billforsythe223]

Can anyone tell me how to change my 9.9 to a 15 ho please

[@chadwassink7846]

Google "Leeroys Ramblings 9.9"; this is an excellent resource for anyone looking to do this. In short, you need to find a Johnson 15 hp carburetor (for this series) with a 7/8" throat diameter and change it out.

[@billforsythe223]

Chad Wassink. Thank you

[@brianchisnell1548]

You need a 15hp prop too or you will over rev.

[@rrrttt1112]

@@brianchisnell1548 What is the stock size/pitch for the 15hp Prop?

[@johnwild3923]

540lbs why far tooo much weight????

[@chadwassink7846]

That is the boats rated maximum capacity.

[@markmccoy8891]

You ever consider a jack plate

[@jamesellis5549]

I put a jack plate on a 12 vhull with a 9.9 Nissan;20.8 mph with me and dog.Helped a lot with spray back into transom.worth doing andeasy to do.

[@chadwassink7846]

9.5 diameter, 10 pitch

[@treefrog9822]

why not just buy a 15hp?

[@chadwassink7846]

The 9.9's seem to be more common. It is simply what I found for sale locally that was in my price range. I did not know anything about the 15 hp conversion when I bought it. I only found that out later, so I kept watching ebay until I found a 15 hp carburetor. To your point, I agree that just buying a 15 hp motor (if you can find one) is much easier.

[@treefrog9822]

good answer.

[@AdamConstantine]

There are also lakes that only allow a 10hp maximum so it’s cool with the mod you can keep food speed fully loaded.