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I have a boat with a 1990 GM 305 in it. Last year I replaced my computer controlled ignition system with a basic HEI / distributor based ignition system. Everything worked great for the entire boating season last year.

This year is a different story. The first time attempting to start the boat, I got grinding noises from the starter when attempting to start the engine. The grinding was so prevalent I was unable to start the boat with any consistency. You could also see the engine clearly kicking back during attempting to start. I also had weird buzzing noises coming from my ignition coil. Long story short, I replaced the 'brain' unit in the distributor which handles the timing and that fixed my buzzing noises from my ignition coil and fixed most of the grinding noises when attempting to start the engines.

I am still getting grinding noises during starting and I usually have to attempt to start the engine multiple times before it will fire. If I remove the ignition wires, I have NO grinding what so ever. Clearly, the grinding it related to the ignition system which would also make sense for it kicking back.

Why would this happen? I have the ignition timed at 8 degrees BTDC as confirmed by my timing light. The only solution I can think of is to retard the timing (maybe something like 6 degrees BTDC) to alleviate any kick-back. This still leaves the question as to why it grinds sometimes and starts others.

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    Go for 5 degrees before - a « standard » or initial point to work from - then see what happens... – Solar Mike Jul 18 '18 at 17:37
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Ultimately I ended up replacing the following and the boat runs fine:

  • Distributor "brain" (mentioned in my initial question)
  • Ring gear on flywheel
  • Battery
  • Starter

The initial grinding due to the distributor caused an entire waterfall effect of issues. The grinding chipped some teeth off the flywheel. Fixing the distributor fixed the primary issue but I was now left with secondary issues: The teeth were really bad on the flywheel so I pulled the engine and replaced that. Even after getting it back together, it still made a "grinding" noise from time to time. I learned my lesson and immediately stopped as soon as I'd hear grinding. I opted to buy a new starter despite the fact that the autoparts store said my starter spun just fine and the teeth looked fine. Apparently there must have been enough internal damage or ware because a new starter fixed my flywheel / starter engagement issues.

Lastly, I bought a new battery for good measure as my last one was 9 years old (optima blue-top however).

All said an done, it was a very expensive and time consuming lesson, but one that I surely will not forget: When your starter is grinding, STOP IMMEDIATELY!

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does your boat have a gm drivetrain? some of those require a thin shim to be under the starter or it presses too hard on the flywheel.

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