Mercury 25 running dirty

[kdh146]

I have recently acquired a '90 merc. 25ELh. the motor, pumps water, shifts gears, and has 130 compressions on both cylinders. What concerns me is that it does not idle smoothly, and after running in a can for 5 minutes or so it seems to have deposited a great deal of what appears to be oily fuel into water through the exhaust. I am thinking of rebuilding or fixing up the motor. What could cause this motor act this way? I have not run this motor on the lake, nor do I plan to until it is runnung cleaner..I have and service manuel on the way and plan to use a different motor for now. Thanx

 

[ddennis]

Re: Mercury 25 running dirty

If it has 130 lbs compression it should not need a rebuild, carbs might, but powerhead sounds fine. What ratio are you mixing the gas/oil?

 

[Robj]

Re: Mercury 25 running dirty

By the nature of the beast, you will be dumping some unburnt fuel and oil into the water. That is how 2 strokes work. They scrub exhaust gases with a portion of the air fuel mixture. Yours may be excessive, check the carb, maybe time for a rebuild.

Have a great day,

Rob.

 

[kdh146]

Re: Mercury 25 running dirty

Oil mix 50-1, and am using the gas left in the take that came with it. I figured that if might be carb. related. When I ran the extra gas out after disconnecting the fuel tank the mortor seemed to run real smooth just before it ran out, last 3 or 4 seconds.

 

[thefairlaneman]

Re: Mercury 25 running dirty

clogged up carb is a good bet .You shouldnt run old gas.The part about using the gas that came with it is a red flag.....How do you know that gas isnt contaminated or degraded?