Starter Troubles again and again

"I have a Volvo Penta Aq271c i

"I have a Volvo Penta Aq271c in a 26 'cruisers and to make a long story short, the re-manufactured 18-5900 starter from napa (sierra has the same) has had the cone cracked twice and now 2 starts into the 3rd, the bendix was stuck spinning and cranking the flywheel, then disconnected but kept whining and I had to disconnect from the battery to stop the spinning, smoke, etc...
Once reconnected it started fine but you know it will fail again. I have heard all the suggestions of hydro-lock,(for the cracked cones), improper shimming, mine had no shims, and I also replaced the bolts. The cables from the battery to the starter a all like new, connections clean and tight.. I guess my question is, are there any suggestions, something I'm missing. Everytime I take the starter back I'm told there is something wrong with my flywheel or shims or whatever. The first time the guy even suggested my motor was siezed. Funny how it runs great every time unless the starter doesn,t do its job. Thanks in advance for any help"

"There should be no Bendix dri

"There should be no Bendix drive on this starter motor. This should be a solenoid/lever type throw-out for the drive pinion.

Many of the PMGR or HTGR starter motors require their own special bolts. The length is slightly different from the OEM bolts..... usually!
If you have the wrong bolts, I'd be suspicious of these being part of the problem.
IOW's, the bolts may be bottoming out prior to chinching down on the starter motor housing.

What is your BASE timing set at?
Could this motor be "Bucking" against too much initial BASE spark advance?

."

"I think you are correct about

"I think you are correct about the solenoid. As far as the bolts, napa also supplied me with the new bolts for the starter which i installed on the 3rd one- and in comparison with the oem bolts they are of the same length. The oem bolts were on the first 2 starters. I have tried to see if there is any play in the mounting of the starter with both set of bolts and I know there is no "give" in the mount but it is possible to have play that is not visible to the eye under the cranking of the engine.

As far as the timing, That is what I am about to check next. What would be too much initial base spark advance. I know the base is 6 degree (idling) btdc and at idle the engine runs a hair below 750rpm as it sits now. Going to get down to slip today to check it out.

Thanx for the direction."

You may want to run these bolt

You may want to run these bolts into the block and take a measurement of the remaining bolt shank length.
See if this corresponds to what's needed for compression at the nose of the starter motor.