Top Carb is Sweating on my 48 spl

So I have a 1990 48 spl. I just soaked the carbs and cleaned them really well and got it all back together and runs great on muffs and also idling at the dock. Finally took it out to run it and it will not make full power. I can go full throttle and push the key choke in and then it will run awesome. While we were out there I noticed that the top Carb was sweating like crazy. The bottom one wasn't. We assumed that the top carb was the problem so we tried to make an adjustment with the needle valve and it didn't matter if it was all the way out or all the way in. I am at a loss. It idles just fine and runs great unless its at full throttle. I could really use some help here fellas....

Re: Top Carb is Sweating on my 48 spl

what does a sweating carb look like? is there water on it? on the outside? not sure what to make of that.

but, I can tell you, that choking the motor should shut it off immediately. Fact that yours runs better when choked means that the motor is running dangerously lean (too much air, not enough fuel).

Because the engine gets its lubricating oil from the gasoline, any cylinder starved for fuel is not getting lubricated, it's getting dragged through a dry hole, so best not to run it like it is.

The needle valve is a slow speed mixture adjustment that does not affect hi-speed operation at all -- your hi speed jets are fixed.

First take the airbox cover off and make sure the throttle valves are closed at idle, horizontal (not beyond) at WOT, and parallel thoughout their range of motion.

Next, check the float height. Held upside down, the float should hang parallel with the carb body.

Then, order two carb kits; replace all the gaskets & o-rings. and the float valve needles & seats.

While you have 'em apart, take the hi-speed jets out & clean 'em manually -- follow the "carb cleaning and rebuilding link" from the "top secret file" at the top of this forum for instructions on fabricating a jet removal tool.

Keep us posted.

Re: Top Carb is Sweating on my 48 spl

What I meant by sweating is that there is condensation building up on the outside of the carb. Enough that it is dripping off the carb. Thanks for the neddle valve info. Im still kinda new to the carb stuff. I will be taking them back off tomorrow so Ill keep you updated.

Re: Top Carb is Sweating on my 48 spl

NC_USCG said:

What I meant by sweating is that there is condensation building up on the outside of the carb. ...

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that's how I pictured it...just don't recall ever noticing it before.............

Re: Top Carb is Sweating on my 48 spl

I have never seen it happen on a outboard engine either, I would be interested in what you find out.

Re: Top Carb is Sweating on my 48 spl

well I rebuilt the carbs and I got the high speed jets out and cleaned them. I am sure that was the problem. They looked pretty junked up. Put it all back together and man is it running better. Took it out and ran it up the creek and it ran awesome. making full power and idling great. Neither carbs are sweating now so Im not sure what that was about. unless the humidity and the fact that it was sucking in more air. No clue.

Re: Top Carb is Sweating on my 48 spl

Strange problem, glad you got it fixed.

Re: Top Carb is Sweating on my 48 spl

NC_USCG said:

Took it up the creek and it ran awesome. .

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Always have a paddle with you when you are up the creek

Re: Top Carb is Sweating on my 48 spl

i think it's just the cold air passing through the carbs

my old 1959 10hp does the same thing. i don't think i've ever seen it on my mercury though? depends on the motor i guess.

dripping off condensations is quite the condensation? my 10hp has only water particles on the top.