25hp merc

5

525

Recruit
Joined
Sep 23, 2013
Messages
4
I have a25hp merc that just stopped dead when I was going about half speed Then I stated it and it idled rough but ran smooth at high speed I have rebuilt the carb and replace all ign componants The bottom cylinder has spark but when I pull the wire off the RPM doesnt change The comprssion on both cyl is 130psi. I'm at a loss to figure this out The bottom plug is wet with gas but has good spark the reed valve looks good Any suggestions?
 
G

goblerblaster

Petty Officer 2nd Class
Joined
Dec 26, 2011
Messages
176
Re: 25hp merc

I had the same issue on the same motor. replaced the powerpack, coils, etc. Come to find out , one of the magnets -located under the flywheel - had come loose and was stuck to the magnet on the other side of the flywheel. I JB welded it back where it was supposed to go- after much sanding and shining of the inside of the flywheel- and it started running like a charm. I don't know how long the JB Weld will hold, but it has made it for a couple of years.
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: 25hp merc

Hello 525, and welcome to iBoats.

Another possibility is the lower seal on the crankshaft has failed. That would allow that cylinder to have compression, but it would not be sucking any fuel in...

Chris.....
 
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