4.3 Starter/ring gear issue
 

I need gear-head help on this one. It seems my summer had been postponed before it has even started. I have an 01 Diablo with the 4.3 and Penta sx out drive.
The issue: grinding noise when trying to start. When, and if it's starts, it runs fine.
The fixes: Motor did not hydro-lock. New plugs and fluids installed so we are good there. Compression checks were good too.

I replaced starter with aftermarket version. While doing so, I noticed a few shavings around flywheel/ring gear but teeth seemed to be more than decent. It started right up. Fast forward 2 days and the awful getting noise reappeared and boat would not start.

I had the original starter rebuilt and installed it. I used the original bolts this time. Same song, second verse... Started once or twice then back to the original issue.

Too the boat to Marine mechanic. He painted starter gears, re-installed, and try to start. Still same issue, and painted gears identified proper alignment. Tried shims for grins/giggles... Not really sure why but whatever. They did not help the situation. He removed starter while I was there and now more shavings around flywheel/ring gear. Teeth still appeared fine. I have seen them work flawlessly in way worse condition.....but still a possibility.

Mechanic believes it needs to go to another mechanic to pull motor and replace ring gear (his hoist recently broken and was awaiting a motor).

I do not disagree with the diagnosis, but I wanted to reach out to the group to see if anyone had a similar issue since I am looking at quite the cost to repair.

The only thing I have left in mind is to try different bolts for the starter mount. I have been using the original ones and tried the ones from the aftermarket starter (seemed to be junk). Also considering replacing power and ground wires to the starter even though volt drop was minimal.