flywheel not engaging with crankshaft, Johnson 50hp 1996.

[janul15]

Hi all, a very recent and sudden problem arose after I have attended to and fixed lots of problems on my Johnson BJ50 BELEDS. The starter motor works, and engages with the flywheel. The flywheel spins, but the crankshaft doesn't turn. I suspect I didn't put the flywheel on tightly enough months ago, and it has now moved . Any suggestions before I remove and refit the flywheel,, and key, and securing nut?

 

[racerone]

Well----Likely the key is sheared.-----Need a new factory key.----Assemble clean / dry and no lube.---Torque nut to 85 FT-LBS.-----Some folks have been tempted and put grease on the tapers.----Big mistake that.

 

[janul15]

Thanks racerone. I'll take off the flywheel and follow your advice. I'm pleased you didn't say the crankshaft may have broken.

 

[racerone]

It would be rare for the 2 cylinder 50 to have a broken crank.---Your description in post #1 sure points to a loose nut / sheared key scenario.------But you right it might be a broken crankshaft.

 

[oldboat1]

^^+++1 on the key. Use an oem key, as suggested. Be sure to get any bits of the old one out, then polish the taper with some very fine wet/dry sandpaper. Inspect the flywheel, and polish the mating surface there too. Leave no burrs anywhere. Clean with acetone to finish.

The flywheel grips to the crankshaft tapers. Be sure to tighten the nut to the spec indicated.

 

[Faztbullet]

Do not polish the shaft or flywheel !! Use some fine lapping compound to "lap" the taper to flywheel. Can be acquired at any good auto parts store.

 

[racerone]

^^^^----Applause on the above post.-----The tapers have to be matched using lapping compound.-----That will get you the correct ---" locking fit "----and that drives the flywheel.----The key merely locates the flywheel for correct timing.-----Note on some model year OMC products the same key is used whether it is a 9.9 HP or a 300 HP motor.

 

[oldboat1]

^^(agree)