Check for frozen engine?

I'm looking at picking up a boat in a few days. Already seen it and it seems in decent condition but I'm a little concerned that the engine wasnt properly winterized. I opened the water strainer - just up from the raw water intake and it had water -not antifreeze in it.

I'll be doing a lake trial to check it out and am familiar with these boats. But I havent ever experienced first hand what a frozen block might behave like.

Where should I look for issues - exhaust manifolds, actual block, etc?

I would presume after up to operating temp the issues would be apparent - what would those be - rough idle, over heating?

Cheers

You should probably get a true compression test to be sure, but one easy thing to do is check the oil after it you have ran it. Once it has been run the oil and water will mix and look like chocolate milk. There is no mistaking it.

Look for damage to the strainer and anything around it. If there was that much water and it froze up there would be damage.

Compression test won't tell you if water broke to oil and didn't effect cylinder, gasket, or head. If oil is not milky and it idles/runs smooth you're likely fine. Compression test and coolant system pressure test are better, but coolant pressure is not quick and easy on a boat motor. Run it hard a bit, turn off, check oil, let it sit a but, start it. If manifolds are cracked it may want to hydrolock on restart after running, and not start. Hard to be 100% sure but if that's all good then you're probably fine.

Check the plug color as well. Black OK, if white, its getting water in the cylinder via cracked exh manifold/riser/block/head gasket/etc.