My laziness = possible cracked block

The RWP priming (or not) wont have anything to do with a cracked block. If you dont have any other indications of freeze damage on the engine (pushed out casting plugs, water in the oil, etc), then dont worry about it. If the RWP now primes fine from now on and keeps the engine cool, then youre fine there as well. If it overheats at speed or leaks externally, then its possible the pump housing froze up and is pulling air. I havent seen that happen myself, but if the RWP was holding water and froze solid, I could see it being possible.

They are there to close off the water jacket. It's really the core used to form the jacket extending into the mold (core print). Such a large core could not be supported by the drain plug holes and intake.

No ice anywhere. When I winterized it, the ambient temp was 50+. It made no sense as to why it would not suck (insert joke here).

I'm not understanding why the rwp wouldn't pull water, or take it from the hose. Are you implying there was ice in the engine that you melted out in the process?

I wouldn't worry too much either...
Like tbeard said, that block can take a lot.

Buddies of mine left their boat outside for two nights while it was lightly freezing (around minus two degrees celcius), before they got to winterizing last winter.
They never had nay problems...

So my procrastination may have cost me my engine. I took my boat out for the season at the end of October. I put it in a detached garage of a house that my wife and I are renovating to rent out. At the beginning of last week, the night time temps here in Michigan were going down to the high teens. I put a space heater in the garage and a 60 watt bulb under the doghouse. The next night I added a space heater under the boat cover. That heater was on a separate circuit from the other one. The next morning I stopped in and found the power to the garage had quit. I found the 40amp breaker that feeds the garage from the house had kicked. That makes no sense, but that's another issue.
Tonight (59 degrees) I took the boat to my truck shop to winterize. I could not run the engine to temp because the raw water pump would not take water from my bucket. I even ran the hose directly in the intake hose, but it would not suck the water. So I drained the block and exhaust manifolds, then refilled the engine with RV antifreeze. For the heck of it, I reconnected the hoses, raised the hull intake hose, filled it with RV, and started the engine. It seemed to take the RV, so I put 3 gallons of RV in a bucket. When I started the engine, it sucked it up like Patty, the day time hooker. I then did a full winterization. If I get a chance, I may run it again to see if the pump is working well. If so, I'll run it for a while and look for any indications of block damage.
Is there anything I should be looking for?

Sorry so long.