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Carburetor Flooding?

T

TGBTG7701

Member
I am trying to figure out a problem I am having with my early 90s Mercury 40 hp 4 cylinder outboard. The motor starts fine when it's cold, runs fine through out the RPM range, but is hard to restart. After the engine has warmed up and I have rode a good distance, I shut the motor off, it is hard to restart after setting for 10-15 minutes. I had to pull up the fast idle and let to rev up for a few minutes before I can lower lever and take off. When it does this the exhaust is very rich, and a lot of smoke, then it clears up and it runs fine. I noticed there seems to be a lot of oil that is dripping from the bottom carburetor, the cowling had a puddle of oil under the carburetor, blue and looked as if it just came out of the bottle of oil. The engine "does not" have the oil injection system anymore, I am running a 50/1 mixture in the fuel tank. I was looking at the idle mixture screw on both carburetor, the top is only 1/2 turn counter clockwise and the bottom is setting at 1-1/2 counter clockwise.

Stuck float?
Adjustment?
 
Pull plugs and take a look at them, light brown,black with soot,steam cleaned, Your starting issue could be caused by excessive heat buildup under flywheel affecting stator assembly when engine is shut off. Your carbs.need adjusting. Sounds like engine is flooding after shutdown,carb issue again
 
TGBTG7701 said:
I am trying to figure out a problem I am having with my early 90s Mercury 40 hp 4 cylinder outboard. The motor starts fine when it's cold, runs fine through out the RPM range, but is hard to restart. After the engine has warmed up and I have rode a good distance, I shut the motor off, it is hard to restart after setting for 10-15 minutes. I had to pull up the fast idle and let to rev up for a few minutes before I can lower lever and take off. When it does this the exhaust is very rich, and a lot of smoke, then it clears up and it runs fine. I noticed there seems to be a lot of oil that is dripping from the bottom carburetor, the cowling had a puddle of oil under the carburetor, blue and looked as if it just came out of the bottle of oil. The engine "does not" have the oil injection system anymore, I am running a 50/1 mixture in the fuel tank. I was looking at the idle mixture screw on both carburetor, the top is only 1/2 turn counter clockwise and the bottom is setting at 1-1/2 counter clockwise.

Stuck float?
Adjustment?
Click to expand...

This is EXACTLY my problem, I could have written it myself. Everything runs awesome until I shut down after a half hour or so, hard to restart, lots of smoke, idles like crap, I have to ride the idle lever. I have decided my floats are garbage, they looked shot when I cleaned the carbs last (didn't think to replace the floats, my mind was on the cleaning job). My new floats arrive in the mail tomorrow, I can't wait to stick them in and RUN LIKE NEW! (hopefully)

Makes sense: if the floats don't float, there's zero pressure on the needle, which has to ride in its seat up and down with the level of the fuel in the bowl. A little arm goes between the floats and the needle. If the needle sits wide open, fuel blasts into the cylinders like a fire hose, no matter the RPM. Flooding occurs, which blows out and recovers once you manage to get moving again. Those silly little floats can ruin your life if they're not in good shape. Oh, and yes, the idle mix screws are mucho importante, too. One quarter-turn can make all the difference between a smooth idle and running like ass. Lightly seat the screws, then back them out equally. Mine runs best at 1 1/4 turns out, but YMMV. Oh, and definitely do that test on the water, not on the muffs.
 
Next time you mess with the carbs, 'vise test' them before putting them back on. To wit: Clamp the carb in a vise and attach your tank. Pump HELLL out of the bulb and see if it leaks--it should not. If so, lower the float level 1/16 inch at a time until it stops.

Jeff
 
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