Volvo penta 5.7gl will not hand crank

[Penta5.7gl]

Stopped engine and would not restart but I initially suspected the battery due to excessive stereo usage (wet sounds, 2000w amps, 10"sub and some components)
I tried a charged battery but the engine only cranked slowly so I stuck with the dodgy battery diagnosis.
I disconnected all additional services and charged the battery but now only a knock and muffled ding so I assumed starter/solenoid etc.
With great difficulty I have tested all the starter side including taking the starter out and watching it engage and spin.
I checked oil levels (fine) and removed spark plugs (no water but mild corrosion on thread) as I was concerned about the "hydro lock" phenomenon!
In neutral and with a 16mm socket and large extension bar I am unable to hand turn the motor, I think the bolt turned / tightened a bit but definitely no cranking!!
HELP Please, any ideas of problem, don't really want to take engine out before winter. Is there a decompression lever on the petrol V8?? I think it's a 1999 model.
Many thanks

 

[RogersJetboat454]

Re: Volvo penta 5.7gl will not hand crank

Welcome to Iboats.

No decompression lever on a Chevy, or really any auto derived marine engine for that matter...
I may not have caught this quite so clearly in your post, but when you attempted to rotate the engine by hand, where the plugs out of all cylinders?

If so, I think your next step is pulling the outdrive to isolate the engine from the drive (a locked up outdrive can lock up the engine since they are directly coupled). Once the drive is off, check to see if the engine is still locked up.

 

[Penta5.7gl]

Re: Volvo penta 5.7gl will not hand crank

Welcome to Iboats.

No decompression lever on a Chevy, or really any auto derived marine engine for that matter...
I may not have caught this quite so clearly in your post, but when you attempted to rotate the engine by hand, where the plugs out of all cylinders?

If so, I think your next step is pulling the outdrive to isolate the engine from the drive (a locked up outdrive can lock up the engine since they are directly coupled). Once the drive is off, check to see if the engine is still locked up.

Thank you for your response, I did have all 8 plugs removed when I tried to hand crank without success,
I can turn the prop in both directions in neutral but I assume to continue fault finding a need to take the boat out the water now to separate the outdrive. Oh Joy!!

 

[RogersJetboat454]

Re: Volvo penta 5.7gl will not hand crank

but I assume to continue fault finding a need to take the boat out the water now to separate the outdrive. Oh Joy!!

You got it!!
I assume at this point with a non-running engine the boat isn't much fun to use as it was before anyway...