# 9.9 to 15



## Timbr (Apr 29, 2004)

Has anyone ever changed the carb and prop on a 9.9hp to "upgrade" it to a 15hp?

If so has it made a significant difference?

Thanks 

Tim


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## bkr43050 (Apr 5, 2004)

I have never done it nor have I spoken to anyone who has. I have read quite a bit over recent years on it. As with most things there are differing opinions on results. It seems to me that more people conclude that you cannot convert the motor to a true 15HP motor. The carburetor is only part of the picture. The exhaust port is unchanged and thus limits the performance. If you are thinking seriously about doing this I would suggest doing some google searches on the topic. You will find plenty of info on this. Also go to www.IBoats.com and search their forums. There are plenty of motorheads in there that have provided plenty of feedback on the topic.


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## Timbr (Apr 29, 2004)

Thanks Brian, very helpful.






Tim


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## mikeshookset (Feb 28, 2005)

most 9.9s can be up graded to a 15 by changing the carbb some motors prior to 1985 also need the exhaust maniflod changed but either way it is a fairly simple prosses


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## wackyworm (May 1, 2004)

I had a '96 9.9 Evinrude with supposedly 15 hp carb, when it died replaced w 9.9 4 stroke Yamaha and the yamaha runs better and stronger than Rude.


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## Erie Addict (Apr 12, 2004)

See this months Bass & Walleye boats mag. they have a breakdown of merc part #'s and steps to do this on a 2 stroke merc 9.9 - 15 HP. around $250.00. Carb, exhaust tube, reeds and a couple of gaskets.They got 2 more MPH 0n top end, but gas milage dropped considerably.


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## bkr43050 (Apr 5, 2004)

Erie Addict said:


> See this months Bass & Walleye boats mag. they have a breakdown of merc part #'s and steps to do this on a 2 stroke merc 9.9 - 15 HP. around $250.00. Carb, exhaust tube, reeds and a couple of gaskets.They got 2 more MPH 0n top end, but gas milage dropped considerably.


 I wondered if that may be the case. I guess my thought on it stays consistent that it is not worth the work to try it.


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## Wormdunker69 (Apr 8, 2004)

Had mine done for around $165 including carb and labor and there is difference. Got quite a lot more speed out of it. Mine is a 1995 Mariner. 
I also know someone that had their Johnson changed over and he feels the same way. Think it over, if in doubt call a place and ask them how much difference there will be.
Bill


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## toboso (Apr 14, 2004)

I am the second owner of an '86 Johnson 9.9 that was upgraded to the 15 hp by way of carburetor, reeds, and exhaust. This was done by the original owner when he bought it. I later bought a larger prop and got the results that the stock prop didn't deliver. The original prop gave me about 10 mph--the larger prop gave me about 13 mph.

I also used another stock 9.9 on my boat and could easily tell the difference.


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