GNJ2

I am using jack shaft kits in a 32 Skater. The kits came with pilot bearings (non-serviceable needle bearing type) for the input shafts going into the crankshaft. I have been told to disgard these, being that these are not necessary and will only be a problem later on. Since the drive plate is bolted to the flywheel and offers support to this shaft, it does make some sense. Can anyone shed some light on this for me?

Thanks - Gary

Tinkerer

You don't need them.

sterndrivespec

if this is a bravo setup i would use some kind of pilot bearing.we fixed a 42 fountain with staggered engines that another shop had replaced the forward engine in.after about one hour of running the flywheel housing would crack.they replaced the housing three times before the owner brought the boat to us.it never had another problem.

GNJ2

Thanks for the info. I knew these must have been a reason Mercury included these.

Tinkerer

The pilot bearing is installed in the end of the crankshaft isnt it.. If that is the case it wont change anything on the flywheel.

Mbam

There is only a single ball bearing in the adapter that mounts on the flywheel housing, the shaft then engages the drive plate. In addition to moving around under load, the center hub on most production drive plates have lots of run-out. So the drive plate causes the U joint flange to orbit, or is not strong enough to prevent the flange from orbiting with the load of the driveshaft on it.

The pilot bearing keeps everything concentric - do not run without it and if it is showing lots of wear check the driveplate, the alignment of the engine to the transom and the balancing of the driveshaft.