Converting a 9.9hp to a 15hp

[fisherman7]

I wrote about having this done some time ago but can't find post. I said I'd update the group when I had a chance to water test it. Well, had a chance yesterday on Couch. I still had to lean forward to get the dingy/inflatable/tender to plane, but once it planed, Holy! I didn't even give it full throttle. Goes like stink.

 

I do believe I have figured out why it won't plane. My inflatable has long tubes that extend about 18" past the transom. Creates a lot of drag but stable when on plane. You lose a lot of interior room though. Live and learn.

[4thgen]

What model and year and how did you convert it?

I looked into that a while ago but found that it was only straightforward (carb swap only) on a few model-years and aside from those, it is more economical to sell the 9.9 and just buy a 15.

[fish-miester]

i heard i can swap carbs from my 9.9 evinrude (believe its a 88) and replace it with a 15.

but how good can that be for my motor?

[bigpikemike]

9.9 and 15hp in johnson and evinrude are the same motor just diferent carbs along with a couple other miner differences.....couple tweeks and u can get it up to 25-30hp...if u want a number of a mechanice that can do it for u pm me

[fish-miester]

I would be interested though Aylmer is a bit far

[fisherman7]

It's a 9.9 Yamaha. All that needed to be done was remove a stop. Mechanic told me it's the only Yamaha model that you do it with.

[2 tone z71]

25 30 hp out a 9.9-15 hmmmm hmmmm not calling Bull just hmmmm,few tweaks eh ,you couldent fit a big enough prop on the shaft to clear the case to make use of all that extra hp the gears in the case would near explode with 30 hp

Edited June 7, 2009 by North East Shark

[DRIFTER_016]

I wrote about having this done some time ago but can't find post. I said I'd update the group when I had a chance to water test it. Well, had a chance yesterday on Couch. I still had to lean forward to get the dingy/inflatable/tender to plane, but once it planed, Holy! I didn't even give it full throttle. Goes like stink.

 

I do believe I have figured out why it won't plane. My inflatable has long tubes that extend about 18" past the transom. Creates a lot of drag but stable when on plane. You lose a lot of interior room though. Live and learn.

 

 

If you don't have one put on one of these Hydrofoils for your motor.

They provide lift at the motor and it will get you up on plane faster and at a slower speed.

 

 

Another option for inflatables is a set of trim tabs like these. If you can afford it this is the better option.

Edited June 7, 2009 by DRIFTER_016