Evinrude 1974 iddles on one

[G DANE]

I repaired my old 1974 Evin 25HP that had a seriour airleak at upper cranckshaftend, this winther. Its on my brotherinlaws boat now. We tested it on earmuffs - it seemed to run great.<br /><br />However after it run for some minutes, it shows a problem, most of the time it only iddles on one ? If you barely touch the trottle, both cyls are on. If you go to WOT in a snap - no problem, both cyls work beautifull, great acceleration. It runs like a champ on all rpm, soft and smooth - no problems, except iddle. What is the problem. The one cylinder turns on and off iddling, RMP going up and down. Compression and spark is fine. We did clean carb. It has run for 2 hrs now - no changes.<br /><br />Im confused, maybe i will change my name to oncylindertwin !!

 

[petryshyn]

Re: Evinrude 1974 iddles on one

>weak spark (compare both cylinders carefully)<br />>too small a point gap on that cylinder<br />>fuel pump diaphram leaking<br />>crankcase or crank seal leaking<br />>reed issues

 

[G DANE]

Re: Evinrude 1974 iddles on one

Thanks Schematic<br /><br />It was an airleak. We put in an extra axelseal beyond the original, as there was a damaged mark on cranckshaft where the upper seal should run.<br /><br />Not a good solution, but the original seal would only last short, due to the rust damaged ring on cranckshaft.<br /><br />This extra seal is steelcapped and forces the "neck" of cranckcase a tiny bit apart, as the turque isnt that strong up there. We´l seal it with fluid gasket.