1987 Mercruiser 5.7 starter grinding intermittently

[ewizard09]

Hi Everyone, I'm new to posting here but I have a problem so perplexing I'm hoping someone can help. The boat is a 1987 Chaparral 200 XLC with 5.7 mercruiser 260 horse and a gen 1 alpha 1 outdrive with a mcm 260 carb. It has a J1171 starter on it replacing a 6562N that came off and a PG260M that I've also tried.

The BIG issue is that my 6562n that was in the boat for about 8 outings started grinding one day randomly. I took it out and had it tested. The bendix was bad. I replaced it with a PG260M with no shims and it worked great. Once. Then it started grinding on the next outing. I took that one back, it tested bad as well. So this next starter (J1171) is the correct one per the mercruiser parts page and I've painted the gears and set the shimming correctly. (Required the "small" shim across both bolts). It starts up fantastic and runs great. I get it hot, try to start it again and BAM grinds again. I've checked the flywheel and the teeth look okay. The teeth are wearing on the starter but look okay. When I put the starter back in with new paint, it rubs off on the tip of the teeth only indicating the starter is too far away from the flywheel (why did it change?) So I add a shim to the outside pad to bring the clearance down. Works great! Bring it back up to hot, restart, SAME ISSUE AGAIN, grinding noise. Repaint, put it back in with the the large shim on the outer pad. Works great. get it hot, GRINDS AGAIN. Check the paint and it is only rubbing off the top again. I've literally taken every shim and a washer to the outside pad and it just rubs on the top of the teeth still. It seems like if I replace the starter, it works. But any time the engine runs at all it might be throwing the starter out of position. I have new bolts, they don't act any differently than the old bolts. I can't measure clearance without the engine out (as far as I know) but I'm checking the gear engagement with gear paint every time. And every time it goes in, no matter the shim situation. I seem to get the same result of the paint being worn off about halfway down the tooth (where it should be). I really feel like either A: the starter is moving or B: thermal expansion of the flywheel and the engine block are so different that it's impossible to set the starter location correctly for both hot and cold starts.

I'm at my wits end here. I've been working on mechanical things for 15 years and am an expert but this one is beyond me. This is the only thing I haven't been able to fix in the last 5 years and we're two weeks, 5 different starters, and 6 sets of bolts in at this point with zero progress.

 

[B Rad G]

I would make sure you have the right starter bolts. The ones you need will be gnurled beneath the threads so it prevents movement of any kind. Also make sure they are the right lengt . Ask me how I know. I tried to use generic starter bolts and it did the same thing. It would start fine after I initially installed the starter. But soon it would be grinding. Even though they seemed tight, they had moved ever so slightly. Hope this helps.

 

[ewizard09]

Thanks! That is one thing I’ve tried. I used generic ones but I spaced them at the head to make sure they were the right “length” I measured the protrusion from the starter on the engine side on the old bolts and matched the new bolts to that. I’ve also tried varying the protrusion with no success. I also measured the OD of the knurl to make sure it matched. It was about 200 micron smaller but was much larger than what the knurl had worked it’s way down to on the old bolts. I really can’t imagine 200 micron would cause this issue. To really check this, I painted the starter up to the engine with a paint pen to see if it was moving and it doesn’t seem to be. I also cranked the **** out of the bolts. On a side note. I’ve been testing the gear pattern paint with the coil unplugged. If I “start” it with the coil unplugged it works great. It’ll start the same every time. The second it starts for the first time with the coil plugged back in so it actually starts. It grinds the next time. Every single time, reliably.

 

[ewizard09]

Some updates! More bolts, more starters, more shims, still the same problems but here we are. I've made a list of what could be wrong. It's either A: the bolted joint for the starter is not sufficient for the loads (Joint) or B: the starter is being overloaded (overload) to be honest it's pretty poor design practice that A can even be a failure mode but moving on.

1: Overload: Motor is seized/water locked - runs great so it's not this

2: Overload: Timing, if the timing is too advanced it can fire on the first upstroke and create too high of a resistance torque on the starter - I tried retarding timing until it started backfiring, still the same issue

3: Overload - Compression: Possibly too much compression or too high of a compression rate because of stuck valves - I'LL BE CHECKING THIS THIS WEEK

4: Overload - In Gear. Out of adjustment shift cables could cause it to have a drag on the flywheel from the prop - I'LL BE CHECKING THIS THIS WEEK

5: Overload - Fuel venting issues: If the fuel pump is working too hard that can overload the flywheel - I know it's not this as this would effect firing or not and my issue is only when firing

6: Overload - Bad crank bearings - bad crank bearings could cause issues with the flywheel going out of balance/round - this is not the issue and it spins over with zero issues through the whole rotation until it fires

7: Joint - Bolts - This is a HORRIBLE design for a starter but the bolt clearance to the starter is VERY important and with bolts that are too small or worn oval shaped the starter cold move. - not my issue as I'm on my 4th set of bolts with no change

8: Joint - Shims - This is again a HORRIBLE design for a starter but I've done gear paint and verified the shimming too many times to know it's correct.

9: Joint - Loose bolts - Obviously this can allow the starter to move. Yet again a HORRIBLE design but I've checked this many times. I'm at 90% of failure torque for the bolts and still have issues

10: Joint - Bolts that are too long - same as loose bolts but less obvious. Tried many different combos with no fixing here.


I'll keep updating as I go. This also covers the list of what I'm working on with the Mercruiser engineers now. I've seen many YouTube videos on cars of this same issue now with a 350 and it seems like what might be happening is the surface on the engine might be dimpled or some other positive retention feature that may wear down over time. So it may be a new engine block for me to fix this