1990 GM 305 won't run after winter season. Odd starting behavior.

[ryno1234]

This is going to be a bit long winded:

I have a 1990 Yamaha Stern-drive with an 305 GM engine in it. Last year after frying the ignition computer that Yamaha put on these boats, I pulled all the computer controlled electronic Yamaha-specific stuff out of the boat and installed a Delco Voyager standard ignition system. Boat ran great all last year.

At the end of the year I put the boat up into boat storage - an indoor storage unit.

I pull the boat down this year and go through my typical pre-season prep starting with making sure the engine is running as it should. While attempting to start the boat a couple of very odd things occurred that I haven't experienced before: The boat would begin to start (you could hear the RPMs during starting increase) but struggled. If i did end up getting the engine to actually fire, I could not keep it running for longer than 3-5 seconds despite giving it gas. While going through this iteration of trying to get it to start, the starter was making an awful sound and grinding against the flywheel. I'd give the starter a break and try again just to hear the starter "clink" against the flywheel but not engage. I'd try again and the starter would engage as it should but only to get the engine back to a place where it would either 1. attempt to start and I couldn't keep it running, or 2. would sound like it was firing, but then instantly the starter would grind.

I used my cell phone to video the engine while I attempted to start it. You can actually see the engine rotating one direction and then reverse directions while I am turning the ignition to start. It is during this reversing of directions that the starter will grind.

I removed my starter and I can see my flywheel has some chipped teeth on it.

To add to all this, I notice when I turn my ignition in the "On" position, prior to cranking, I hear my ignition coil make a whirring noise for 1-3 seconds and my digital RPMs gauge on my dash go from 99 (x100) and continually drop 99, 95, 88, 81, 74, 65, etc. for the duration of the whirring noise coming from my coil. I thought this might be my coil so I purchased a new one. The new one didn't do that the first time I turned the key on, but after trying to start the engine once, the brand new coil made the same sounds and did the same thing with the RPM gauge the following times I turned the key to the "On" position.

So, in summary:

• Boat doesn't want to stay running despite giving it gas once starting
• Starter is grinding against flywheel and it is apparent that the engine literally turns in the opposite direction for a short period of time.
• Flywheel teeth are chipped now because of this
• Coil is making an odd noise. This may be normal, but I'm not ruling anything at at this point.

I've thought the following could be it:

• Pre-ignition on certain cylinders causing engine to rotate in the opposite direction.
• Hydrolock
• Issue with coil / ignition system causing odd / wrong firing

I'm at a complete loss and my next move was to remove the engine and put a new flywheel on it because regardless, at this point, I know my flywheel is damaged to a fair extent (I can still crank some of the time, but the starter doesn't engage perfectly like it used to). Even still though, that wouldn't fix my issue.

I've attach pictures of the flywheel teeth and a video of a few attempted starts.

Any ideas?

Thank you!

Grinding / Counter-clockwise rotation.

Grinding / Counter-clockwise rotation.

Ignition coil noise + RPM issue

Ignition coil noise

Starting issue / grinding

 

[Scott Danforth]

start with cleaning the battery cable connections on the starter, block and battery.

 

[ryno1234]

Thanks for the input. My battery is fully charged and the terminals are clean.

 

[ryno1234]

I forgot to mention an important piece: If I disable the coil by removing the power, the engine does not kick back and the starter does not grind. This tells me it is clearly some sort of ignition issue causing the kick-back.

 

[Maclin]

The ignition timing is off now for some reason. Maybe the timing chain has slipped a cog. Could be internal to the distributor, like the pickup coil inside the distributor moved or came loose, or the distributor moved from where you left it clamped down, or the distributor shaft is compromised. I would backtrack all the steps you did when installing the distributor, and remove it and take a look.