99hp Mariner 2 stroke 2001 Conversion to a 15hp

Can anybody out there advise m

Can anybody out there advise me how to convert the 9.9hp to a 15hp motor. I've heard you have to change the carby and other things. What other things?
Thanks
Bob

Gotta be some porting involved

Gotta be some porting involved for a hp boost like that.

Jeff

"Robert, you can (boost&#4

"Robert, you can (boost) the 2001 9.9 to a 15 horse. The 1995-on 9.9/15 horse shared a powerhead.

You need to replace the carb with one from a 15 horse model (about 225 bucks new from Merc)

and pull the powerhead and replace the exhaust plate and tube (which comes as a single unit - about 60 bucks)

and of course throw in a new exhaust plate gasket and powerhead base gasket, cheap at about 15 bucks for the pair).

And once you have done all that you will get almost 2 more mph out of your rig at wide open throttle (actually the best I did in tests that I performed was 1.8 mph, but I guess 2 is pretty close) and you will burn 15% more gas all the time.

You gotta ask yourself, is 2 mph worth 300 bucks and a few hours of your time?

Or you could do it and lie to yourself about how much more power your rig has.

Moving from a 9.9 to a 15, even though it's a 50% horsepower increase, just doesn't not make the kind of difference most think it will.

If you want a change you will actually see/feel, you would have to move from a 9.9 to a 25 horse at minimum....."

"You did have it correct Jeff,

"You did have it correct Jeff, it's just that Merc conveniently did the "porting" on the base of the carb itself and the exhaust plate (with an extra 1/4" diameter exhaust tube on the 15 horse), both of which are removable.

I guess it made production of the two models easier that way.

That also does make the retro-fit easy - just not worth it...."

"Thanks very nuch for the info

"Thanks very nuch for the info Jeff anc Graham, your right Graham a couple of miles per hour isn't worth the expense and time. I'll stick with the 9.9hp it's real reliable.
Regards
Bob"