Dinghy outboard help

[Mickeyrouse]

It’s not clear- is this the best place for seeking advice on the 5 hp for my dinghy? If not, where?

[Shrew]

Yes, this is a good spot. What is the issue you're having?? Please include year, make and model.

[Mickeyrouse]

The outboard in question is a 2002 (ancient, no?) Mercury two stroke, 5 HP. Though I bought it new, I doubt it has 25 total hours on it. It was rebuilt after a sinking 15 years ago, and has run fine ever since until now.
I last used it 3 years ago. In preparation for an extended cruise next year, I am tuning things up. Knowing that the carb was probably gummed up, I removed the carb and soaked it overnight in carburetor cleaner. Re-assembled it and now I trying to make it run consistently and smoothly. After fuel is flowing (or so it seems) the engine will crank and run wide open. Then it shuts down, after running maybe 5 seconds. Choking or un-choking doesn’t make much difference. Lotsa spark according to the spark tester, lotsa compression, lotsa air. Obviously the problem is too much fuel, then none at all. I can wait a few moments, crank and it does it again. Clearly it points to the carburetor. But just what?

[Shrew]

Originally Posted by Mickeyrouse

The outboard in question is a 2002 (ancient, no?) Mercury two stroke, 5 HP. Though I bought it new, I doubt it has 25 total hours on it. It was rebuilt after a sinking 15 years ago, and has run fine ever since until now.
I last used it 3 years ago. In preparation for an extended cruise next year, I am tuning things up. Knowing that the carb was probably gummed up, I removed the carb and soaked it overnight in carburetor cleaner. Re-assembled it and now I trying to make it run consistently and smoothly. After fuel is flowing (or so it seems) the engine will crank and run wide open. Then it shuts down, after running maybe 5 seconds. Choking or un-choking doesn’t make much difference. Lotsa spark according to the spark tester, lotsa compression, lotsa air. Obviously the problem is too much fuel, then none at all. I can wait a few moments, crank and it does it again. Clearly it points to the carburetor. But just what?

Too much fuel?? The jet itself can only provide so much fuel. Too much fuel would be an imbalance (insufficient) air. Does it idle at all?

Honestly, I don't mess around much with carb rebuilds anymore. The rebuild kit is around 75% of the cost of a new carb. A new carb comes with new jets, mounting gaskets and is assembled. This is especially the case since the outboard took a swim. I don't care that it used to run fine for years, it's not running now, it's old, ethenol is a 'thing', and it's been submergred in saltwater.

[wholybee]

I recently bought a new carb for my similar vintage Nissan from Amazon for about $50. imho it isn't worth fixing a worn out carb for that price.

The Mercury and Nissan might be identical models.

[skyhawk]

doubtful the carb is worn out with so few hours on it.
Corroded....well, perhaps.

Not familiar with newer outboards and carbs, so this line of thinking might be off base. I've rebuilt several outboards...but that was 30+ years ago.

Did you remove the needles when you soaked the carb?
I can imagine a possibility that the small orifices just didn't get cleaned sufficiently.

and if you did remove the needles, it can be a trick to get them set right again.

I'd wonder if the fuel pump could be bad. Have you cleaned it? Running wide open but only for a short time makes me think starvation. Can you pump the hose bulb while it's running?

I trust you're using new gasoline....
I'd start with verifying the pump
then I'd be sure to remove the needles (carefully counting turns) and shoot carb cleaner through each very well....

[Mickeyrouse]

Yeah, I found the carb I need on eBay for $79. It’s ordered. BTW, the present carb was replaced about 4 years ago.