90 hp Merc Help Please

[gmb]

I have a 1999 90 hp Merc. Recently i used valvetec marine motor decarb spray. I took the boat out today for first time since doing that and it wouldnt idle very well. I ran it a while slightly revved (about 30 min)and it seemed to be working fine....except now it misfires every now and then at idle and seems to be running high rpm at idle now. I also have noticed gas leaking from the cowling when tilted all the way up. Is there gas leaking in the carb???Please Help

 

[Plainsman]

Re: 90 hp Merc Help Please

After I decarbed mine I had to clean the plugs. Also the decarb will loosen a lot of junk and it has to get rid of it, so it may run alittle rough until all that loose stuff is gone.
The rpm's may increase because it's running better because of the decarb.
Does the gas leak with the motor down, or just when tilted up?

Others, with more experience, will be along to help you I'm sure

 

[Silvertip]

Re: 90 hp Merc Help Please

It is not unusual for fuel to run out the carb when tilted up all the way. Your coffee cup does the same thing when tilted. A float bowl is the same thing as a coffee cup. It's full of fuel. Tilt it far enough and the bowl runs over.

 

[Texasmark]

Re: 90 hp Merc Help Please

Give the decarb time to work and as Plainsman said, change the plugs, or at least clean them.

I decarbed mine ('02 90) last year and have kept SeaFoam in the fuel.

I had it out a couple of days ago. I had not had it out for a couple of months but had run it on the hose in the interim. It was a cold day.....meaning it really needed time to warm up.

I launched with a pretty normal start; hit the fuel enrichment the couple of times it wanted to die; let it idle at the dock while parking to give it time to warm up.....seemed to run ok. Got in and went out to the nowake buoy and took off with a moderate throttle.

It shuttered and balked and it was obvious that I was only running on 2 cy. I gave it some more throttle and waited. It planed out and pulled on out of it and the 3rd cylinder cleaned up and kicked in....running smooth now. Hammered down on it and went to the normal WOT mph. Everything is as it should be.

Had no more problems the rest of the trip. Started right up and no more missing.....don't know what it was.

Nothing like running one on the water to see whether you have any problems or not.....the muffs aren't the answer.

HTH

Mark

 

[gmb]

Re: 90 hp Merc Help Please

Thanks for the reply....maybe Im just paranoid. It does seem to run a lot better now that I cleared it out...maybe just a little too much. Ill check the plugs and see if that will correct it. I did notice Before i decarbed the engine that when I tilted it all the way down it would leak some gas ouf of the exhaust i assume (right hand side of the midsection). I havent noticed that happen though after decarbing. Thanks for all the replies. Ill try to keep everyone posted.

GB