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Stuck 3.0

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69birdman

New member
I tried to start my motor that has been sitting for a few years. Won't turn over.
I charged the battery, pulled the plugs and still won't turn over.
Next I pulled the head to take a look. There was a little rust around the the last piston.
Not sure how water got in. Condensation maybe? I used some penatrating oil but still won't turn.
What can I do to get this motor unstuck. The motor is a new replacement with about 15 Hrs. on it.
GM 3.0 in a 99 Larson 18' bowrider.

Thanks for any help you can provide.

Dave
 
You can try a few things. Put some diesel or Marvel Mystery Oil or similar on top of the pistons and let it soak for a few days. You can then try to tap (gently) with a piece of wood on any piston that is not on TDC or BDC. Then, if the engine does not move with the starter, you can try using a pry bar on the flywheel teeth or removing the front pulley and using a socket wrench breaker bar and a piece of 1" pipe to turn the crankshaft.
 
Years ago I did a similar repair. The upper gear box had taken on water and had rusted and would not move.
When the transmission was removed, the engine turned over freely.

However, on this model, I'd think that the rubber hubbed drive coupler would offer some slight movement that could be seen at the piston.

Apply some heat to this piston deck, and see if that helps any.
 
I used Marvel Mystery oil and am letting it sit until Saturday. I will give the pistons a tap.
I don't know what position the pistons are in. Going up or down. Does it matter?
Can't get to the flywheel, front pully is hard to get at with the motor mount in the way.
The drive is still attached.
I will report back. Thanks for the help.
 
No.... it should not matter which direction that you attempt to move the piston. Once it begins to move, you can change directions.

Are you familiar with a PPS (positive piston stop) procedure?
There are several methods used to stop a piston as to index the harmonic balancer to locate true TDC.
One method is described bellow, and it gently stops #1 piston for a PPS procedure.






Notice the steel plate that is bolted to the cylinder block via cylinder head bolt pattern, and notice the adjustable piston stop bolt.

Fabricate yourself a similar plate that can be bolted down to the cylinder block via the head bolts.

Use a much larger PPS bolt...... let's say 1" or so. This will be your "jack bolt".

Place a brass plate on the piston deck to protect it.... perhaps use a rag or piece of leather between the brass and piston deck.

Now crank down on the 1" jack bolt.... similar to how a puller tool would work....., but in reverse.

The 1" bolt should place enough downward pressure on the piston deck to start it moving downward.

Like said...... DO NOT use this on a piston that is near TDC or BDC. Use one that is ONLY near TDC, or partially down.



Edit:

Here are two other versions of a plate style PPS.
Imagine these center bolts being 1" (or ???) and with heavy enough female threads to safely jack against.








.
 
Last edited:
Well I made a piston pusher tool and the piston moved very easy.
Turns out I only needed a starter. Seems I removed the head for nothing.
The motor is running as it should.
The starter that was in it was fairly new. When I tried to start the motor it sounded like it would engage the flywheel but not move.
The battery cables would also overheat. After pulling the plugs and again trying to start it - same thing. Thats why I thought it was stuck.
Thanks for the help. I am glad it was an easy fix.
 
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