20hp Mecury possible carb problem

[KnightZ1001]

I have a mid to late 80's model merc. 20 hp motor. It cranks great, it idles good. On land I can hook up the water hose and it runs like a champ. My problem starts the moment I run it in the river. It will run slow speed just fine, but when I go to open it up it accelerates and then starts choking and stuttering. I can accelerate slowly and reach plane if I'm easy on the throttle, but if I move the throttle the least bit faster of slower it will start stuttering(for lack of a better word). I've used carb. cleaner, I've taken the carb off and opened it up. Everything looked clean and good, I'm stumped, please help.

 

[Laddies]

Re: 20hp Mecury possible carb problem

It sounds like a dirty high speed jet, might as well clean the carb and be sure to ck the jet for varnish

 

[KnightZ1001]

Re: 20hp Mecury possible carb problem

I took the carb apart last night and cleaned it, didn't really need it, it was not all that dirty. The guy I got this motor from told me that he had just changed the spark plugs in it and that he thought that all it needed was a new fuel filter. Within the first week I found out that there was nothing wrong with the fuel filter and the guy had put 2 different sized spark plugs in it (neither of the two where the right size, nor the right gap setting). I fixed the spark plugs, thinking that might be the problem. Helped out a little bit but I was still having the shimming issue when ever I excoriated. After we had pulled her out of the river one trip out, my wife and I ran into someone we know and asked them for advice. They said they had a the same problem at on point and that they had placed their hand just above the cab. intake and letting the suction pull their hand onto it for a few moments and that had back fired and blew out the problem. My wife, not wanting me to do anything she deemed stupid, told me to try eather. We did that and it helped, but still the same problem. Some one else I meet said they to had the same problem and that I needed to use some Deep Creek as well as Sea Foam and that would fix the problem. Did that, still got the same problem, not to mention that fact that I go through a tank of gas 3 times faster then I did when I had my Johnson 9.9 or the Mercury 9.9 that I traded the guy who I got this motor from. So this is where I stand as of now. Any ideas would be greatly appreciated.<br /><br /><br />Laddies, you said check the jet. I do not have the repair manual for this motor and to be honest I am a decient shade tree mechanic on cars, trucks, and motorcycles, but I am a beginer when it comes to boat motors. I am afraid I am going to need a little clearification on that one. Please feel free to e-mail me any diagrams or what ever you feel might aid me in repairing this problom. BarnBurner001@hotmail.com <br />Thanks for any and all help you provide.

 

[Bob H.]

Re: 20hp Mecury possible carb problem

Not familiar with that carb but problem is typical of clogged jets or mixture adjustment. If you can't adjust the air/fuel mixture you'll need a rebuild kit and pull the welsh plugs for a good cleaning. Is the gasket between the carb and block in good shape?

 

[Motor Boater Bill]

Re: 20hp Mecury possible carb problem

It is strongly recommended that you not use ether in an outboard, this washes the lubricating oil off of the internal parts and can damage the bearings. If you need to spray something in the carbs use oil/gas mix. WD-40 has also been suggested but I have no experience with that.