I just read the first page did not see SteveH's post...... I think he has it there for ya!

Check bolt length too. My bolts were bottoming out but it was not noticeable until you cranked the starter and it would shift down a few thousands of an inch.
A knurled indexing starter bolt is mandatory as recommended in the previous post.

I guess we'll have to check that all out because I had the starters rebuilt before they went on last year so, we'll just have to take a look and see what's going on.

This has been a very good/informative thread. Thanks for all the input from everyone. "HELP...I'm in starter hell" ---still too funny!

well i bought a new gear reduction starter,with new bolt put it on and it seems to be working good i will cross my fingers and hope i dont have to pull it back off

Dyno, On the older Chevy blocks mostly in 4X4 trucks the machining tolerance on the blocks weren't so great. We used to always try to keep the starter with the original block but when you couldn't then you have to either shim the starter or machine the mounting pad down, depending on wether it is to tight or to loose. Shimming is easy if it's to tight. Sounds like your's is to far away from the flywheel. If you can see the contact of the gears, take the solenoid off of it and manually engage the starter. If it's not deep enough then you can either mill the mounting pad down or I have filed them down to raise the starter a little at a time to get the tooth contact you like. Should be deep in the ring gear with out bottoming. Hope this helps. I'm in michigan also, been running to Muskegon a lot lately, if you can't get it. Let me know.

I just converted my 502 blower motors to 540 NAs. The old starters wouldn't even think about turning my motors over without hooking them directly to my duallie batteries, but then they smoked like hell. I bought two new starters from www.mesmarine.com - they work like a charm (I think the model is MES-5399MHT)! If they won't turn your engines over, something else is wrong. No shimming or anything...

I have changed over 100 starters. I never ever had to shim.
Usually something is wrong with the starter nose. If I ever had a problem I used another starter. Starter bolts also are different from regular bolts and align the starter better. BBB

Just an update on my post from last spring. Both of these #@$%$ starters have now knocked teeth completely off of my flywheels. When it happened on the starboard engine, I attributed it to something I did. Now it's happened to the port engine, and I can hear indications in the starboard that it's happening again. It's late in the season and I don't feel like pulling both engines, so I guess my season is over.

Also had this problem this summer with a customer that needed a starter.
Changed starter and found out manifolds let go and let H2o in motor and he tried to start it and with the high torque starter. It is very possible to remove a few "flys" from the flywheel due to ingestion or other issues ! Unfortunate for him he had to pay big money to have someone else change the $13 ring gear because I was way too busy, and he needed the boat for the weekend and still didn't get it in time... BBB