Low power, cylinders/carbs choked with oil?

joeboater7

Cadet
Joined
Apr 23, 2012
Messages
27
Hi,
After spending more than $2000 with the pro's I am coming here for help. I have a '90 115hp mercury outboard. Usually runs great. But after an hour or so of idling one day recently then storing the boat in the garage with the motor on the transom saver, then next time out it did not want to start. When it did start, it let out a ton of smoke. Then i could not rev it over 3k rpm, and in gear I couldn't go over 7 mph. I was able to tell some of the cylinders/carbs were not firing. I took it home and took out the plugs (which are only a few weeks old), and noticed they had some oil on them and also dripping out of the plug holes slightly. I soaked them in rubbing alcohol and put them back in. Took it out again.. and same thing.

Last summer it did the same thing with no power, so the mechanic said carb rebuild and new plugs. $1000. But after just a dozen outings it is messed up again.

A few summers ago, the same thing.. a carb rebuild.. it worked for a while, then within a few weeks it failed again.

In the past if I use a lot of seafoam and/or just drive around a long time, slowly suddenly it starts to spurt / surge with more power.. Then eventually it can clean itself out..

motor has good compression.

Maybe the oil theory is the wrong theory here. Any ideas? I believe this motor only fires on all cylinders over a certain rpm. Maybe it is injecting oil in the cylindars not in use during times when i am driving slow? And sometimes the build up is too much?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,977
The bottom 2 carburetors do not put enough fuel in at idle.---4 cylinders spark at idle.----Bottom 2 carburetors start working at 1800 + RPM
 

joeboater7

Cadet
Joined
Apr 23, 2012
Messages
27
The bottom 2 carburetors do not put enough fuel in at idle.---4 cylinders spark at idle.----Bottom 2 carburetors start working at 1800 + RPM
Are you saying this is normal for the engine and I just need to maybe adapt to it? Would your suggestion be to always run the engine on high rpm before exiting the lake?
 

joeboater7

Cadet
Joined
Apr 23, 2012
Messages
27
What do you think the fix is to get it working normal again? new plugs?
What do you think I need to do to avoid this in the future?
 
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