Re: Late 80's Mariner 9.9HP convert to 15hp?
I not sure for your motor but I have a 9.9 1982 Rude and was doing some research for it.
You can get some more HP's by just putting a carb on it but not the full extra 5hp.
Needed to get the exhaust and a intake valve shim from a 15hp too. Basically to allow for more air in(Shim) and more air out(Exhaust) of the motor needed to make the extra HP.
My rude went from 9.9 to around 12-13 1/2 HP. To get the full 15hp I needed the intake/exhaust hardware too.
Now I know its a evinrude but I wanted to give you and idea of the situation. With that said Im going to do some research for your engine now. What is your Model and/or Serial number ?
I'd say if your really want more power , clean your 9.9 up sell it and grab a younger 15-20HP.
1990's and up. The 1990's and up motor probably will be lighter too. 10-15 Lbs lighter.
What are you using the engine for Cruising/Speed fun or need the extra HP's for loading a boat up for fishing?
Thanks,
DamianJP