Could do a compression check and maybe narrow it down to a cylinder. Then pull that head and if the problem is in the head you won't have to pull the entire motor. If the head is OK then turn it over and see if the piston is coming to TDC. Got a feeling if you truely hydrolocked it you may have a bent rod and it's hitting the bottom of the cylinder.

My bet would be a bent rod or rod's . Had a friend that had a similar problem a few years back and that's what happened .

when u fill that cylinder with water,rods do bend,and pistons also break or it might have dropped a valve seat,that gets real ugly.

80psi coming ont of a garden hose? I think that sounds high but if it's correct I would guess that it pushed past the head gasket and filled the cylinders with water just before starting. I always turn the water on just after starting to avoid static water pressure in the system for that reason and shut the hose down at the same time as shutting the engine down. just saying, 80 psi is alot, IMO. I hope it's good news when you tear it down but it doesn't sound likely. At least its winter. Trying to look for a bright spot I guess.

80 lbs seems really high to me also,my hose is good for maybe 4 lbs,thats why you need to keep it at idle rpm,the water pump sucks more than the garden hose can provide above idle.

I use a bucket with a hose atached to the bottom to the muffs. Let the hose fill the bucket. Let gravity feed the engine. Never had a problem!

My hose pushes at least 40 lbs, but wont push water past my raw water pump. It also does not even come close to keeping up with the raw water pump as far as flow. It regularly sucks the garden hose flat at anything over an idle.

I agree with Philm - unless you bypass the raw water pump, the engine never sees 80 psi. Mine runs 70 psi, and I get no flow until cranked.

This is what I'm thinking due to the noise it made cranking it over after I pulled the plugs out

I don't want to turn it over any more, and do more damage. I squirted some oil in the Cylinders to hold it over until I pull it out.. I've already made up my mind I'm pulling it.

After pressure testing the Manifolds, and running water through the risers, and finding no leaks, I have to conclude that this was self induced... Too much hose pressure I guess.. God I've done this a hundred times.

I can't imagine that water can go past the pump.. at a higher volume than the pump is pumping. Does that even make sense?

The idea of using the 5 gal bucket sound like the safe bet. Good one, and soon to be my new process