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Haunted Cylinder


AMK's Avatar
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06-17-05, 03:50 PM   #1  
AMK
Haunted Cylinder

I have a 3 cylinder, 60 hp, Merc Model 60, circa 1985. Last year the motor would start right up, but only run on two cylinders. After 10 or 15 minutes of running time the third cylinder would kick in and the motor would run fine the rest of the day. I've changed spark plugs, and done some preliminary tests on the wires and the coils. The shop manual does not list this problem in its troubleshooting section. Any ideas?

 
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papasmurf's Avatar
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06-17-05, 07:55 PM   #2  
Did you do a compression and spark check?

 
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06-17-05, 08:00 PM   #3  
Cylinder Not firing when cold

Suspect low compression in the cylinder.

Do a compression test (on all of them) when cold - then again when all seem to fire.

Compression rises when the engine is at operating temp because pistons swell
to fill the cylinder better end I suppose rings expand to lessen the end gaps.

May only require new rings. Might also run satifactory for limited use as is.

A flooded cylinder due to inadequate compression for firing is the probable state of the engine at the cold start..


 
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06-18-05, 07:23 AM   #4  
AMK
Thanks for your input guys. I did a spark check and all three seem fine. I'll do cold and hot compression checks now.

 
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06-19-05, 05:13 AM   #5  
Another possible cause could be a head gasket leak between the water jacket and one cylinder letting the plug get wet and fouled out until it gets warm enough to dry it out.
I had this happen on a 2 cylinder at the end of boating season and figured I would repair it during the winter then found significant rust in the bore 2 months later.

 
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06-19-05, 07:34 PM   #6  
No head gasket on that motor. Just a water jacket.

 
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