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new 9.8 four stroke won't idle

B

bax

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After two months of light use last fall, I relaunched my boat a couple of weeks ago and had an issue with one of my two motors. My friends helped move the engines frm the car to the boat. Much to my chagrin, I saw that they were carrying one with the head lower than the lower unit. After install, it was leaking oil out of the plastic carb intake cowling when engine was tilted up. It wouldn't start, no surprise. Pulled plugs, and cranked it over, oil everywhere, cranked a bit more till no more came out, cleaned up mess, cleaned plugs, added a little oil to replace what was lost out of the cylinders and tried again. Still no luck. Removed drain plug from carb and pumped bulb till oily fuel turned clear. Replaced plug and voila! She ran fine. Got us out of the harbor, motored for about 10 minutes later on to get to the mooing. Next morning, it wouldn't idle. It starts at mid throttle with choke, but will only stay running at high rpms.
I thought perhaps I had added a little too much oil to replace what I purged out of the cylinders, so I sucked a bit out to get it well below the top hash marks.

Could it be that it was too high and some oil clogged the jets? The engine was brand new last fall, carb was run dry before storage. Any ideas? Thanks!
 
Bax,

Sounds like a lean-at-idle condition. There may still be some oil lurking in the intake silencer (carb intake air box). Are you still getting any oil smoke? If crankcase oil ran through the breather hose (likely), that might still dribble for some time. Otherwise, it's possible that there was some debris in the carb bowl that got mixed up in the fuel flow, and sucked through the main jet, and is now in the low-speed or idle passages of the carb. If the problem persists, pull the carb, disassemble (completely, including jets and the emulsion tube nozzle), and clean all passages thoroughly. If you are careful, the removal can be done while the motor is on the boat, but beware of dropping parts into the water, as they usually don't pass the float test. Considering the amount of time to pull the carb and disassemble it, I usually give them a full 4-hour soak in real carb dip, followed by a thorough spray-out with generic carb spray, and then reassemble.

Remember that you must always, religiously, run the carb dry at the end of each and every day (unless you are 100% sure you will be running again the next morning), to reduce any varnish residue from accumulating in the small passages.
 
Paul,

I am still seeing a little smoke, so maybe that is it. I guess I will start by pulling the intake silencer and the breather hose and cleaning them out first, then if no luck clean the carb as you suggest.
Can one routinely use Stabil or something like that to avoid running carbs dry after every use?

Thanks again,
Lincoln
 
Stabilizer is OK. It will slow the "rotting" of the fuel. Around here, we have found K-100 (the MG, or Marine/Gas formula) to be about the best. But it will not prevent evaporation, and that is where the residues come into play. The best way to reduce varnishing always was to run the carb out. With today's fuels, it is critical.
 
Problem solved! Pulled carb, disassembled and cleaned per your recommendations and voila! She runs great. Will use the Stabil I bought and run them dry after each use. A bit of a pain, sure, but it beats the work involved in cleaning the carbs.

Thanks Paul !!
 
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