I have what i understand to be a Gen VI 525SC engine in my boat based on the block casting number (10237297) and the 6 bolt timing chain cover etc. I have looked everywhere and have not been able to find the actual serial number anywhere. My starter went out at the beginning of last season and i have replaced it 2 or 3 times , once with a mercruiser starter and once or twice with a sierra. Each time the new starters have not lasted very long. Start making noise and then go out. I have researched and spoke to mercury many times trying to make sure i have the right part number. According to mercury reps and the applicable materials, all 525sc up to Gen V in 1996 used one starter (50-863007a1), and the Gen VI from part of 1996 on used another (8m8021116) . From what i can tell the later is a little heavier and higher torque. Both are active part numbers. Does anyone know what the actual difference is in those two starters and why a different one is recommended for the Gen VI? Are they interchangeable? Do i have enough information from the block casting number etc. to know i have a gen VI? I realize i could have had some junk starters or maybe a flywheel issue etc but i just want to make sure i have the right part before putting another one on. It is a real pain putting them on with the engine still in the boat. Lol. All help is appreciated. Thanks.

I run 525 long blocks and in my opinion there is nothing special about the starters or blocks, I bought 2 after market starters and they have worked perfect for 3 years you may have an alignment / shim issue or a ring gear problem

I have a few tubs of parts from my 525sc’s. I am pretty sure at least one if not both of them had a shim on the starter. I will try to look tomorrow, if not it’ll be this weekend and see what I can find with the shins and starters.

Thank you so much for your help! The Mercury rep mentioned I might need shims. Look forward to what you find.

very nice!

sorry, running behind but it is still on my list.

Thanks again. I appreciate it

Low voltage kills starters too. #1 reason actually outside of being submersed.
Be it battery, connections, or cables.

There is a real possibility you need to shim the starter. If a starter is not shimmed correctly it will lead to premature failure.