The evinrude 9.9/10hp carb change to make it a 15hp urban legend.

[moxie-man]

Is it true or not that the same years 9.9/10 evinrude needs only to exchange the same years 15 hp carb to get 15 hp? Or is more required? I think someone thought it might be the 79 to 82 vintage motors.

[pappy]

Only in the later engines. You can check the parts lists from Marine engine to confirm what year the change was made to add the tuner in all of them. Too lazy to do it for you!
The changes included the carburetor, shims under the reeds, and a tuner in the exhaust in place of a pipe. Oh, and a propeller change.

[Mumbles]

The link below will help to explain the differences in the two motors. Depending on the year, just changing the carb might not get the full fifteen horses out of the motor but it will make a noticeable difference.

http://www.leeroysramblings.com/Johnson%209.9_15.htm

Here’s an ’84 9.9 which I woke up by just changing the carb. It rocks now on a light boat!

https://www.youtube.com/watch?v=wTK67n5P9DE

[moxie-man]

Thank you Mumbles. That is the info I was looking for. It is much more exact than I expected. I will now start looking for the the motor and carbs plus other parts if needed for a project of this scope.

[r-c]

Those 9.9 and 15’s had so many changes through the years it is hard to keep up or even remember all those changes. 1974 to 1993? Before the bigger 15 cubic inch model.
There was a time I think in the early models, it was just a smaller carb. When they went to the actual tuned exhaust, which really helped the mid range, it was not only a carb change but the cylinder head also had less compression than a 15.
When we had the Evinrude dealership and there was a near by lake restricted to 10hp or under. We sold a lot of 15’s and bought 9.9 hp decals. That was until "aqua fuss" got smart and learned the model numbers. We had to go back to the parts book and figure what we needed to make a 9.9 into a 15. Cost was pretty expensive to the customer. But the customer is always right.

[Alan]

I did this swap, and was very happy with the results!

Mine is the earlier style, which does not use the tuned exhaust, and I did not get into the reed valves; just a carb swap.

I don’t bet that I’m getting a full 15.0 horsepower out of it, but it’s a lot stronger, and pushes our 19′ aluminum boat quite well. It even got me home, (several miles in rough seas), when the main motor quit. A windy day, with four adults on board, and we motored back quite nicely.

Happy motoring!
Alan

[moxie-man]

Alan,

What year engine is your 9.9 and 15 hp carb.

Bruce

[Alan]

Hey Bruce;

Apologies for the delay; been busy with work, (my least favorite four letter word).

My motor is a 1979, and I’m not sure what year the carb is. The carbs are available on feeBay, but I got mine by posting a free want ad on this site, for a lot less $$$. The carb swap was no big deal, and gave me the opportunity to adjust and dope the float.

If your motor’s been in salt, or has trouble getting enough water through it, ya might check / replace the upper water tube grommets. Ya have to take the powerhead off, (which I generally prefer to avoid) but mine had the old style grommets, which had begun to expand. Honestly, it took twice as long to deal with the tiller handle than it did to do the impeller, seals, and grommets. The pivot bolt was salted / frozen. Now I have a green handle on a (rattle can) white motor, but the original paint on the handle was too pretty to paint. Again, the handle came from a free webvertize ad, and was a fraction of the cost of the options available elsewhere.

Below are the before and after pics; I’ve enjoyed this motor, and I hope you have fun with yours.
Happy motoring!
Alan

[PugetSoundBoater]

Alan-good to hear you got that tiller handle replaced. Jim

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[moxie-man]

Alan,

Thank you for your info and photos. I will definitely go forward and plan on building one.

Bruce

[Author]

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