Late 80's Mariner 9.9HP convert to 15hp?

mahones

Cadet
Joined
Jul 18, 2012
Messages
7
Hi Folks

I have a late 80's Mariner 9.9 and I've heard that some of these motors can be converted to 15hp with a carb switch. How would I know if this is possible for my motor?

Thanks for any help you can provide
 

Jlawsen

Master Chief Petty Officer
Joined
Apr 22, 2012
Messages
810
Re: Late 80's Mariner 9.9HP convert to 15hp?

I'm pulling this out of my rear but I think 1989 was the first year that you could do that with same year motor parts. If I recall, the jump was from 9.9 to 20hp for 88 and earlier. In 1989 they made the 15hp. Merc had found a way to offer different hp ratings using the same engine and only changing the air and fuel. The obvious way to do this would be to start with a bigger motor. If the 25 was also the 20 then the 15 might also have been the 9.9.

I don't think you can shove that much fuel down the early 9.9's without rasing the ports and opening up the exhaust. If your motor is pre 1989 the answer might be no. One thing for certain is that the carb to do it with ais no longer available new so you'll need to hunt one down on Ebay or Craigslist and then rebuild it. Most of the parts are still around.
 

DamianJP

Chief Petty Officer
Joined
Mar 25, 2008
Messages
605
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
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: Late 80's Mariner 9.9HP convert to 15hp?

If its a 9.9 that the Yamaha import and yes a carb change along with opening the reed stops .110, a 9.8 will not as block is different.
 
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