Converting 9.9 Merc Two-Stroke to 15hp

[Sunspot Baby]

I have a 2002 Mercury 2 stroke 9.9 outboard. I understand the 9,9 and 15 hp engines are exactly the same except for carburetor and prop. I need to convert my 9.9 to a 15. Does anyone on the forum know which carburetor and prop are standard on the 15?

Reason: My Zodiac compact RIB was rated at 10 hp max. It was stolen and when I replace, I will buy a dinghy rated at 15. Rather than operate with less power than the boat can effectively use, or buy another motor, I think the best option is to convert the one I have. A new carb and prop will be a lot less than the $$ difference if I sell mine used and buy a new 15.

In answer to your question the dinghy was not stolen from the boat. I had it in a locked storage yard on my little utility trailer. Both are gone. I seldom use the trailer and it is nice to have the dinghy out of the way when we are doing our summer projects on the boat I don’t see either often. I’m not even sure when they were taken.

The engine, oars, anchor, etc were in my garage, so all I lost was the dinghy. Looks like my boat insurance is going to cover the dinghy loss with a $250 deductible. Home owner’s won’t cover trailer unless it was stolen from my property.

If anyone is offered a good deal on a West Marine (Zodiac) 10’ compact rib, check the number. Mine is WMP P3907 C 404.

A reward is offered for information leading to recovery. Private message me on this forum.

George

[Sunspot Baby]

I am adding this note to keep this string active. Someone on this forum probably knows the answer.

George

[Doghouse]

15 hp Carburetor........Part # 1392-9726T18
15 hp Exhaust kit........Part # 41344-T6
and Gasket kits

Those are your part numbers. I google searched on mercruiser outboard conversion 15 pages of potential results. I did not search that far in...

[Sunspot Baby]

Thanks Doghouse. I just got on to post the same info from the smalloutboards site.

George

[Sonny]

I wonder if this works on other outboards or is this just typical of newer Mercs

[Vasco]

Most 9.9's are detuned 15's. Check with your dealer.

[Sunspot Baby]

Sonny:

The reason I pursued this was that in another life I had an Evenrude 9.9 that could be converted to 15 simply by changing carbs. A prop with more pitch took advantage of the 50% increase in power. I lived on a private lake with an HP limit of 10. Being able to make a stealth 15 out of my 9.9 was a very appealing option. Driving a 16' pontoon boat that extra 5 hp made a big difference. Still the little john boats with 8 hp ran off and left me.

George

[dutch45]

Hey,

I have a 1996 merc 9.9 2 stroke outboard and im looking to convert it into a 15. I know that I need a 1392-9726T18 Carb, but is there anything else. Exhaust kit possibly? Thanks

[Chief Engineer]

Are you sure that it only needs a carb

Are you sure that the bore and stroke of a 9.9 is the same as a 15?

[Roy M]

I took an outboard repair class last summer from a local community college. My assigned motor was a Mercury 9.9. The difference is the jet in the carburetor. All the other goodies are the same engine. The reason? California freshwater areas are apparently limited to ten HP.

[phorvati]

mercury parts website used to have an easily accesible parts diagrams. It seem weird that 9.9 and 15 had the exact same parts diagram. There were several carbs listed as options 9.9 and 15 bein two of them. Next time I need a carb, i might just order a 15HP.

[Roy M]

What's weird about it? The costs involved in engineering, production, inventory, training, etc., are big. If someone realizes they can meet a bureaucratic regulation that opens an entirely new market, simply by removing and replacing a single, cheap component, that deserves some credit, don't you think? Oh, and I forgot the other difference: You have to change the decal on the motor housing from 9.9 to 15, or buy a different housing.

[Sunspot Baby]

I did this on mine. At first I was told I needed, a couple of other parts in addition to the carb but a local shop looked up all the parts for me and the carb was the only change. Works great.

I carry the old 9.9 hp carb as a spare.

George

[AnchorageGuy]

Originally Posted by Roy M

What's weird about it? The costs involved in engineering, production, inventory, training, etc., are big. If someone realizes they can meet a bureaucratic regulation that opens an entirely new market, simply by removing and replacing a single, cheap component, that deserves some credit, don't you think? Oh, and I forgot the other difference: You have to change the decal on the motor housing from 9.9 to 15, or buy a different housing.

Why change the decals? Or is there some regulation requiring this? The lower end outboards like the 9.9 are lees likely to be stolen and 15 HP seems to be the starting point for theft.

[phorvati]

Hey George,
do you notice the difference now. I mean can you get up and plane with bigger load then before?
My main motivation is the ability to plane, with grocerries, and full gas tank or with an extra person.
Petar