'78 115 johnson

[RichardG]

Recntly rebuilt 115 with all new elec. except flywheel, runs in spurts at higher rpms with a sputter at idle. This is a intermentent problem that usally occurs after a restart. Everything is new and electrics have been checked at RAPAIR. Does anybody know the symtoms of a leaking crankshaft sealing ring, or a weak flywheel magenet? Fishing season is leaving us behind, can anybody help?

 

[12Footer]

Re: '78 115 johnson

A leaking seal will "show". Lots of goo around the crankshaft,and flung all over the <br />inside of the flywheel.A compression loss will also be observed,especially the top jug.<br />If you lose compression,you lose the fuel pump's power to pump,causing fuel fuel starvation.<br />A weak flywheel magnet will give a weak spark,your plugs will foul very fast.<br />A surging RPM at high speeds could be a symptom of fuel starvation. Sputter could also be, but to a lesser degree. If the motor has been under repair for a long time, the fuel left-overs probably went bad in the fuel line,pick-up and bowl, varnishing everything up.<br />Just my 2cents.Hope you find it. Let us know what u find.<br /><br /> <br /><br />------------------<br />the Early bird get's the worm...So, he don't have to stop for bait.

 

[JB]

Re: '78 115 johnson

Hey Richard. Heed what 12Footer has told you, but don't get cylinder compression, which you measure at the spark plug hole, confused with crankcase compression/vacuum, which operates your fuel pump. A bad crank seal will leak both pressure and vacuum from the crankcase of the top jug, and, if that is the cylinder that runs your fuel pump it will not pump properly, causing fuel starvation, the top jug wont make full power, you will get gunk under the flywheel and eventually oil up and kill your magneto. <br /><br />Since you say that she was recently rebuilt, the above problems are not as likely as a gunked up tank pickup, fuel filter or pinched fuel line.<br />Good luck.<br />JB

 

[RichardG]

Re: '78 115 johnson

THanks for your reply 12 footer, upon further<br />investigation today we found a crack in the fuelpump valve plate. This could be affecting fuel delivery which would explain the surging at higher rpms. There is not but one way to find out and we will keep you posted. Any other words of advice are greatly appriciated,and wish us luck.