Neet to convert 9.9 to 15 hp

[geokeco]

I have a 2002 Mercury 9.9 2 stroke s/n 0T194481.

My dinghy, which was rated for 10 hp was just stolen and I am changing to one rated for 15 hp.

I understand the only difference between the 9.9 and 15 was carburetor and prop. Can anyone tell me the correct carb and proper prop to change this to a 15? It would be far cheaper to convert than to sell my perfectly good motor used and buy a new 15. Or is it a simple as re-jetting my carb?

I am aware the prop doesn’t change the HP, only takes advantage of it. Greater pitch

Thanks

 

[DHPMARINE]

Re: Neet to convert 9.9 to 15 hp

Best bet would be to go to Merc's site,and look at the parts book and compare the 2 motors.As an example,you can change some Johnson 20HP to long shaft,but few people realize the motor and gearcase rubber mounts are different,as well as other parts.

A quick look told me the carb throttle plates are different,so the throttle bore is probably larger on the 15,meaning yes a new carb ($185.00).Also the exhaust plate/adapter under the power head is different.The 15 is probably larger.

So it's not easy.Your new dinghy may run better @9.9 than a half botched 15 conversion.Motors are pretty much an air pump.What you put into them,needs a way to get out.

DHP

 

[WillyBWright]

Re: Neet to convert 9.9 to 15 hp

There is only one proper way to convert a 9.9 to a 15 and you don't have to buy any parts or use any tools. It's called "Trade-in".

The bad news is that your 2-stroke 9.9 is probably just as fast as a 4-stroke 15. Or maybe that's good news for your 9.9. Used 15 2-strokes are a little easier to find now as they get traded-in for 4-stroke kickers. But it's still a pretty tight market.

I see jetting mentioned all the time. Simple jetting is not, has never been, and will never be the difference in horsepower. Carb throat size, reed block configurations, cylinder porting, timing/throttle configuriations, exhaust tuning, induction method, gear ratios. Some to all of those account for different horsepowers from the same bore and stroke.

 

[Silvertip]

Re: Neet to convert 9.9 to 15 hp

AFA Marine is advertising 9.9's that have had the 15 HP kit installed and they even list the part numbers. I won't list the link but "smalloutboards" is part of the link. Otherwise Google or Yahoo AFA Marine and look at their motors.

 

[geokeco]

Re: Neet to convert 9.9 to 15 hp

Thanks Silvertip. That's exactly the info I needed.

 

[WillyBWright]

Re: Neet to convert 9.9 to 15 hp

"The motors have their 9.9hp Decals still on them. The Mercury 9.9hp and 15 hp Use the same engine block and weigh the same. The only difference is the Carburetion and Exhaust."

The first sentence concerns me. Not necessarily for your situation since your new boat is rated for it (I assume). But this is fraudulent, and downright illegal in many states if you are hanging the motor on a boat not rated for it, or using it on a lake that doesn't allow them. An "honest" conversion would include new decals. It might not affect you now, but if you knowingly sell that motor and it ends up on a boat not rated for it, YOU could end up in serious litigation if there is ever an accident. My strong advice would be to get a 15Hp decal set. It is extremely important that the horsepower be properly represented. Mercury yanks dealership franchise agrements for what they are doing. Certified mechanics that routinely perform such conversions risk having their certification yanked. I'm astounded they haven't...yet. I will guarantee you that every single warranty (including parts warranties) they submit ends up in a special pile at the factory once they get wind of this, no matter what horsepower. Their playing with fire ends getting their customer burned. I would never deal with a business that operates with such a flagrant penchant for facilitaing cheating. Doesn't matter if they do the work or you do. They are the ones assembling these "conversion" kits. All you have to do to make it an honest conversion is get the 15 decals and use them, or remove the ones that say 9.9. Cover your asss. If you happen to have any warranty left, kiss it goodbye.

 

[WillyBWright]

Re: Neet to convert 9.9 to 15 hp

I don't have 2002 parts info at hand. This is from 1999 models. I know of no changes made to the final years of the 2-stroke line, but I'd assume Merc wouldn't put R&D money into motors that were nearing obsolescence. The crankcase and reed block numbers are different between the 9.9 and 15. That would lead me to the conclusion that the carb and exhaust are NOT the only differences between the two motors as this particular dealership advertises. Let the buyer beware...

One more thought you should consider before dealing with these people. If they are OK with cheating the law, if they are OK with cheating the factory, who else do you suppose they are OK with cheating?