Engine Cooling Question

Grandpa has a 1990 era inboard (not a CC) with a 351 Ford.

Last fall the boat went from running fine to running hot....really hot all of a sudden. Grandpa attempted to fix the boat several times by installing new lake pump impellers because the impellers were melting repeatedly.

By the time grandpa decided to stop trying to fix it he had melted the plastic cover on the flame arestor and melted holes in the exhaust hoses and had chewed up about 3 lake pump impellers.

He brought it home from the lake for me to look at, examination found a lake pump impeller that was chewed up bad and a lake pick up line that appeared to be kinked between the lake pick up and the inlet to the stainer or the transmission cooler. I also noticed that the engine mounts had broken loose from the stringers due to rot and had moved forward about 3".

I was sure the engine movement forward was the reason for the lake line being kinked and most likely the main contributor to the whole over heating problem by causing the lake pump to not have water.

Over the winter he had new stringers installed and the engine remounted. We then installed a new lake pick up line, new exhaust hoses, new lake pump, replaced the spark arestor, belts, thermostat, new oil, oil filter and spark plugs.

Ran the boat in the driveway with a fake-a-lake adaptor and the boat started and ran with no problem and showed no signs of over heating during 30-40 minutes of operation.

Launched the boat in the lake last night for a final trial before returning it to KY. Ran it for 10 minutes at idle speed while grampa parked the truck, by the time he was back to the pier the temp was at 160 and just a few minutes later we were approaching 200+. I shut it down before he had a chance to try to "fix" it and burn everything up again.

Any ideas of where the overheating problem might be coming from?   I have flushed from the inlet to the lake pump backwards to the lake pick up and there is no obstructions in this line. Under the pressure of a garden hose on a fake-a-lake adaptor I am getting water all of the way through the engine and it is exiting through both exhaust.

I have considered that maybe a blade from one of the many lake pump impellers that were destroyed last fall was circulated into the engine water pump and has clogged up the water path. I have also considered that maybe the water pump on the engine has went bad? It is not leaking or squeeling.....but the pressure of a garden hose would mask a bad pump.

I am open for ideas, suggestions, and help.

Thanks,

Scott