[catalyst-519]

Hey Guys:

Having a carburation prob with my 1976 9.9 Evinrude. It's been modded with a 15hp Carb. Pulled it apart (clean as a whistle)and it looked like it had a kit in the last couple years so I sprayed it out again and put it back together. Problem is that there is no lower end and it stalls at low idle. Also at medium idle it will run but then sometimes rev up really high without touching the throttle. I've had it in at the mechanics and they say they have set the low idle as good as they can get it. They claim that the low compression 100/100 is the source of the problem as the motor does not have enough compression to draw sufficient fuel into the cyls, but I don't fully believe this as I have other motors that will run well with 90/90.

The only thing I may have done wrong is when removing the float valve seat I scored the face of the brass with the screw driver as it was seized in there good. Instead of replacing it I just cleaned it up with some emery. Didn't touch the inside of the seat, only the face. Could this be causing the problem?

Any ideas would be most welcome at this point.

Cheers---519

[R.Johnson]

Besides trying to make a 15, out of a 9.9 , what other changes were made? Changing the carb will not make that engine a 15. I never compared them side to side, has that 15 carb got a bigger throttle bore then the 9.9? If so, that would exsplain the sluggish low end. Why not put back the proper carb?

[catalyst-519]

Yes the 15hp carb has a bigger bore. On this year and model the only difference between the 9.9/15 is the carb bore, otherwise it's an identical motor.

I bought it modified and only realized it once I pulled the breather off the carb and saw that a 15 had been stamped in black ink into the carb body. So I guess I could find a used 9.9 carb and throw that on, but would want to be certain that that's the issue before sinking money into that.

[catalyst-519]

So do you think that going back to the smaller size carb is the solution. I've read a great deal of this mod for this motor and no one seems to mention a low idle difficulty. I guess it always could become a problem as the compression starts to decrease but 100/100 should be more than adequate. . you'd think.

Any thoughts?

[CATransplant]

You're right. On that model, the carb is the only difference, and that's probably where your problem lies. If I were you, I'd pull it, and clean it properly, with a soak in carburetor cleaner for all the metal parts. Follow up with a thorough blowing out of all orifices, including removing the core plugs to thoroughly clean the passages under them. Put a new kit in it, including that seat.

Your compression is fine, and the guys in that shop were blowing smoke up your leg. If it won't idle, there's a problem in the carb, especially if it's running OK at other throttle settings.

Your low speed jet is adjustable. Be sure to check the needle for any scoring, and pay very close attention to the main jet orifice plug, which must be sparkling clean, with no burrs or any other abnormalities.

Once you're done, your 9.9 will be putting out the 13 or so hp it's supposed to.

[catalyst-519]

Thanks Cat:

See the thing is, I've done the cleaning. Except I didn't do a new kit because it looked good and had an replacement kit on it already. Low speed needle is good to.

So you think I should just kit the 15 carb that's on there rather than drop back down to the 9.9 carb?

How do you remove the core plugs and how do you reinstall the new core plugs after?

Cheers---519

[R.Johnson]

Lift the power head, pull out the exhaust tuner, see how alike they are. 5 HP gain on that tiny engine with a carb swap. Should of went with the 25 HP carb

[dimock44]

I am sure you read Leroy Wisner's web page. If not do so it's very good. I agree about the Carb being the problem. If There no problem you can sometimes get away with just cleaning but If your fighting a issue you shoud soak it and put un a new Kit. Good luck and please let us know when you get it resolved. Thats how we all Learn

"http://www.sschapterpsa.com/ramblings/Johnson%209.9_15.htm"

[CATransplant]

Originally Posted by R.Johnson

Lift the power head, pull out the exhaust tuner, see how alike they are. 5 HP gain on that tiny engine with a carb swap. Should of went with the 25 HP carb

Go to the BRP site and have a look. In 1976, the only difference was the carb. They made more changes in 1977 or 1978, but it's only the carb in 1976. Those 15hp motors only actually made about 13.

I checked this out for another thread.

[CATransplant]

The only way to really clean and repair a carb is to do the soak, blow, and kit. Spraying stuff just doesn't cut in on the tiny orifices in these carbs.

As far as the core plugs are concerned, you carefully punch a hole then pry them out. Replace them with the new ones in the kit, then use a pin punch roughly 1/3 the diameter of the plug and tap it (not too hard) to expand the plug into the hole. No sweat.

[catalyst-519]

I'll repost after it's done. Thanks for all your help guys.

Cheers--CAt519

[Capt.Nick]

Originally Posted by catalyst-519

I'll repost after it's done. Thanks for all your help guys.

Cheers--CAt519

Is it done yet?

[mcjuddy]

Howdy,

I have a '76 15 hp, that I purchased with a 9.9 carb in it (unknowingly). If you are still having problems, and want to swap carbs for the proper one, let me know.

Cheers,
Greg
"looking for a 76 15hp carb"

[ChrisAG]

Originally Posted by CATransplant

Go to the BRP site and have a look. In 1976, the only difference was the carb. They made more changes in 1977 or 1978, but it's only the carb in 1976. Those 15hp motors only actually made about 13.

I checked this out for another thread.

When did they (or did they ever) produce that generation of engine with an honest 15 hp?

[jay mendoza]

I sent you a PM detailing what you need to do to fix your problem, check your messages!

[Tacklewasher]

Year old thread bumped by a newbie guys.

Original poster hasn't been here since April