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2006 Mercury 8hp 4 stroke

D

doug_bryant

Regular Contributor
"I have a problem with my 8hp.

"I have a problem with my 8hp. I changed the plugs, lower unit oil, and crankcase oil a couple weeks ago. Well, my eyes aren't what they once were and I overfilled the oil. Ran the motor with too much oil and it started out the day great but gradually the performance deteriorated. Now it is hard starting, won't idle, and runs a little rough. Same symptoms as a dirty carb. So my question is this: on these little 4 strokes, can oil be forced into the carb due to an over fill condition and affect performance?"
 
"overfilled 4strokes tend to p

"overfilled 4strokes tend to push excess oil fumes[and oil] out thru the crankcase breather,into the aircleaner and consequently into the carbi,thus fouling the plugs..in cars and land based motors,it means buying new air filter elements,not cheap.and new plugs of course"
 
"It depends on how much extra

"It depends on how much extra oil you put into the engine. If it was only a few ounces it probably would not be a problem. If you filled the engine right up to the top of the crankcase, it could cause trouble.If the intake fills up with oil it can get into the carb through the main horn in the carb bore."
 
"Well, the guide says 800 ml o

"Well, the guide says 800 ml of oil and I put in a full quart, 950 ml. I removed the carb today and cleaned out the jets and the bowl. Re-assembled the carb and started it up. Runs better but not quite there. I am soaking the carb in Seafoam overnight and then I will put it back on the boat and go run it for a couple hours."
 
Get a spraycan of Merc's &

Get a spraycan of Merc's "Powertune" (sells for about 5 bucks) and follow the directions on the can. Does a nice job of cleaning up an "oil flood" - all kinds of "cooties" come out the exhaust...

And keep it handy - works really well if the motor is layed on it's "wrong side" and the oil seeps into the cylinders that way too.
 
Pull the plugs and pull the st

Pull the plugs and pull the starter through a few times...Any extra oil in the chamber will be blown out
 
"I don't think five ounces

"I don't think five ounces of oil would cause a big problem. If the oil level reaches the lower crank bearing or the lower cylinder bore it could cause the oil to get thick and foamy, which would interfere with the lubrication system. This would be obvious when you look at the oil in the oil pan.

It would take more than five ounces of oil to cause the oil to get into the intake through the crank ventilation."
 
"I have ruled out the over oil

"I have ruled out the over oiled theory. I had the carb apart yesterday and I cleaned it all out. Re-assembled it and started the motor, still won't idle. Runs ok at higher RPM but kind of has a surge to it. I'm going to replace the fuel filter Sunday AM and wheel it over to my brother's house for some instruction. I've run Seafoam through it, Mercury tuner, and cleaned the carb per the Mercury factory manual. I've missed something but I don't know what it is."
 
"All fixed. I missed something

"All fixed. I missed something in cleaning the idle jet.
"
 
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