I picked up a core engine from a junk yard and while I was doing enough of a teardown so that I could get it out of my truck I put a wrench on the alternator bolt to see if the engine would roll over. To my surprise the engine rolls over. Have any of you had experience with aan type 4 that's been underwater?

I would say its completely trashed.

Bearings are most likely done, tear it down. see what is salvageable.

Don't let it sit too long. It will freeze up and do damage eventually. Tear it open, how long since its been out of the water?

That will be the million dollar question there was quite a bit of water that came out of the cyl enough that they had to have been almost if not full. there is some evidence of water being in the intake tract , rusty water, so a tear down is in the immediate future for sure. I'll try to post some pictures of the carnage.

I had an engine that took in water. I even started it before I realized something was off. I drained the oil and it came out cream coffee color. After draining, I put in new oil and a new filter and it was FINE......

Results may vary.

Rust does not happen as much under water.
Now that is out, it will sieze up.

Strip it all the way apart as soon as you can.

I had a motorcycle that that happened to as well. I considered it a hand grenade but it ran well until I sold it. I did tell the guy who bought it the history so he knew going in.

It makes me wonder what the oil temp is in the case..... probably close to vaporizing...

My son flooded the boat a few years ago.
It had over 5 gallons of salt water inside.
I drained and changed the old 5 times, ran it and changed it.

Thing ran fine after that.

I bought a 1.8L engine a while back with carbs. The engine had been sitting outside and was seized. I drained the oil to find about 3 quarts of water in the oil.

Removed the plugs and squirted oil and WD40 in all the plug holes. Slowly I started jogging the motor to free it. Got it to turn just a little bit. Then a little bit more and so on. Finally got it fully turning.

Compression seemed ok so I put FI on it and ran the engine for the last 4 years. No problems.

Same experience several times, cleaned and ran them, a few quick oil changes and no problems. I think it depends on the length of time, if it was totally submerged, how dirty the water was, etc, etc, but if you can drain it, replace the fuel and electricals and run it, get it hot enough to evaporate the rest of the water, you might be good. Not much to lose by trying, worst case is that you'll end up tearing it down, which is what you'd be doing anyway.

After a teardown due to leaves and evidence of dirt and silt down the oil fill area I found a crack and a disintegrating cylinder in number 3 jug the crack ran the entire length of the cylinder and the is a chunk missing from the top of the cylinder. It looks like it went out of the cylinder past the valves but without cleaning up the head I can't see if the seat is OK. The rod bearings are not bad other than wear the crank journals will clean up but no rust just need cleaning cam same thing.

Photos

2nd that


But always thought these were air cooled

Not water

Why didn't your son drain and change the oil 5 times??

Good one!