1989 Mercury 25HP won't idle....

[jim2029]

I have this motor and I can't get it to idle. It will rev up great when you can get it started. Starting usually means priming the blue button on the carb a few times. Here is everything I've done to it.

Rebuilt Carb, New champion spark plugs, Check spark (OK), Compression is 110 and 107 top to bottom cly, Flywheel key is alright. New fuel hose, bulb, and fresh non-ethonal gas mixed 50:1.

I have idles the motor up but when i goto throdal it down it doesn't idle down so I have set the idle back down.

Any ideas???

Thanks.

 

[oldgradywhite]

Re: 1989 Mercury 25HP won't idle....

I would replace the plug wires its made a big change for me.

 

[jim2029]

Re: 1989 Mercury 25HP won't idle....

I have thought of that but it runs great at wide open. I've also done a sync-n-link on the motor.

When it dies out its almost like its running out of gas, no popping, missing, back firing... but almost like a key is turned off at high rpm.

Tomorrow I'll run my meter on the wires and see where they check out at.

 

[jim2029]

Re: 1989 Mercury 25HP won't idle....

I think there is a crack in the carb, so I ordered a new carb.

 

[jim2029]

Re: 1989 Mercury 25HP won't idle....

I found the problem...

On the revalves there is a rubber gasket that is shaped like a blocky C and half of it was gone... and all over in the crank case... Pluse the crank case gasket was also gone... so I order a gasket kit and regasketed the motor, and it runs as good as a Mercury can run...

 

[Dkrager]

Re: 1989 Mercury 25HP won't idle....

Wish I had seen this post sooner. I went through this last year and found the bad reed gasket, after taking the carb off 10 times!!! I think running ethanol blended fuels may have something to do with it. Mine was just eaten away.

Glad you figured it out!!