the crank bolt???? crank bolt has a 3/4 head on it and all I have done is tighten the bolt about a 1/4 turn and I am afraid of snapping it. This is in my boat that has sat for over 4 months and the engine is froze-up.........
I did spray PB blaster in all the cylinders and then topped them off with marvel mystery oil and let em soak for 24 hours.

Of course I don't want to snap the crank bolt and I am wondering if there is an alernate way to spin the engine over?? Maybe attach a harmonic balancer puller the crank pulley and use a giant breaker bar? I just replaced the starter and it will fail if I try to start an engine that won't spin...... TIA TBF

Can you get at the flywheel with a prybar?? I think once you get it broken free a little, you can go back to the crank bolt to give it a few more rotations.

No clearance at all towards the back of the engine.... I am going to go out and remove the crank pulley. I am going to go to the junkyard and try to match one up. My idea is to weld some steel tubing to the outside of the pulley and then stick my breaker bar in the tubing and let it rip. That should allow alot more torque than the turning the center bolt..... I need to think outside the box like "MacGuyver"!! TBF

maybe a nice long chunk of angle iron. drill two holes that match your pulley and crank away.
might want to let that solvent soak longer. I assume you do not want to take the heads off, If you did you could tap on the cylinders a little. do you have the spark plugs out?

Oh yeah... plugs are out... removing the engine from the boat is a big deal and I want to avoid that at all costs....
I posted this question on another site and a marine mechanis said to use a large strap wrench around the pulley.... I did not even know they made them any bigger than the oil filter ones but sears has them..... TBF

Pull the balancer and use a crank socket.

For watt its worth I had a locked up /6 that I tried to break free w th crank bolt (3/4)
used a 6 ft pipe on breaker bar and ended up rocking the whole car on the suspension before I gave up. They ran it lo on oil then topped it off before selling. $100 Junk yard motor fixed that and gave 20+ mpg

I dont think you will break that bolt but attaching to the balancer or a crank socket is a better idea

I am confused (not that tuff fer me)
what is a crank socket?

Like this:

Sweet tool, that is kinda what I thought.
I have been lucky and not needed one yet but good to know. Will one tool fit all mopars? How much?

Then you can do this:

If you try to use the pulley, you'll bend the hell out of it.

You are vewy kweva gwasshoppa.... Thanks for idea Barry, I did not even think of that as well. This is a 454 chev so I am sure they make them. I got a sears strap wrench and hooked it up with my 6ft long pipe "torque multiplier" and it snapped the cheezy rubber strap "el-pronto'..... Being the MacGuyver that I am. I grapped an extra serpentine belt and it just happened to fit in the tool. I gave that a try and it fit in the pulley nice and snug but when I started putting some serious force on the end of the pipe it snapped the aluminum handle......... Maybe a real big strap wrench would work but I must have been putting 500 ft/lbs of torque at least on it before it snapped. I puled a riser and found water intrusion so i have some rust issues that must have caused the seizure. The plugs did not look that bad with no rust on them?

Thanks for the ideas guys, I was trying to get this thing fixed before I go in for shoulder surgery next week so this project will have to wait...... TBF

once you pull the engine, your machinist will love you..

there's really no reason not to pull the engine. if it's locked up that tight it needs to be rebuilt or junked.