Mercruiser 3.0 squeal keeping engine from starting

[nola mike]

Yes, I was thinking with me adding the STP oil treatment helping to keep the engine running instead of that noise stopping the engine makes me think it is internal. Or, whatever that is snagging in the flywheel area (ie a bolt head, etc) just cut through enough that it was allowing the engine to also continue to run. I’m not sure, still trying to figure it out.
Thank you for the continued help, everyone. I really appreciate it.

I still think you need to turn it over by hand to feel where it's binding. I doubt oil treatment would make any difference. Running without load on the engine might. I'd be surprised if there really isn't a way to access the damper enough to turn it over, but I don't have experience with the 3.0

 

[Scott Danforth]

I would have pulled the motor by now and got i on a stand and had the pan off.

if its back by the flywheel, it may be a core plug coming out

if its internal, you could have a spun bearing

 

[Sunburn71]

The flywheel isn't serviced with the engine in the boat unless there's a trick I'm not aware of. It might stand to reason that you would need to lift it out to properly inspect / repair that anyway. I am lacking knowledge in that specific area because I am a car/ truck / EV technician and not a boat tech. I am sure someone with more specific knowledge might chime in.

 

[1997BR176]

Thanks again for the replies, everyone. I found this video I first took when I picked her up. Now paying better attention to it, it does sound like there is a faint rod knock but didn’t know any better back then. I’m starting to really think it is internal in the engine. I will have to take engine out and drop the pan and inspect.

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