Interesting starter failure

This is a new one on me. Tried to start our 60hp Merc 4 stroke the other day. No starting occured. Instead there was a horrible screeching noise.
Checked the usual culprits: Bendix not fully engaged, so the starter gear chewing up the flywheel. Nope, fully engaged.
Battery weak, so starter chattering instead of turning? Got the monster battery out of Serenity. Nope, battery fine. Connections all good.

Had someone turn the key while I watched. The starter turns, bendix runs up the shaft, fully engages the flywheel, then stops. But the starter shaft keeps turning inside the bendix assembly. Hence the dreadful screeching noise. Never saw that before.

A new Mercury starter is around $500 Cdn online. But the gear, bearing etc that engages the flywheel is available at Crowley for $45. Apparently it's a suffiently common failure mode you can buy that part. TIL it's called a starter drive.

 

If you can't wait, tack weld the parts together.

 

I am under the impression that there should be a Sprag bearing in the collar as shown. Or some method of applying the start motor torque to the flywheel but if the engine starts, the flywheel will not spin the starter motor.

This collar does not really resemble say a V-8 engines bendix, but there looks like there is room for the bearing inside
Welding the two together would negate the ability of the bendix from possibly releasing from the ring gear/flywheel teeth as often the teeth will have a bit of a burr on the backside.
This burr can sometimes hold up the bendix drive gear from releasing keeping the pinion engaged.

So perhaps in your case, the bearing is slipping, obviously and defunct

 

That's a strange failure.

Was there an opportunity for a pull cord to be employed?

 

I thought so, but the 60hp doesn't seem to have that feature. At least, I couldn't see it.

Sprag bearing! Never too old to learn a new term. Yes, that has failed.

 

Before you install a new unit, check the flywheel teeth for a burr/feather on the backside and remove with emery cloth/file/stone.

 

Will do.

 

Barry raises a good point.
It lead me to think why.
What is the cause of this failure.
More importantly, what to do to avoid another failure after replacement?

EDIT: It may be prudent to replace the ring gear at the same time.