What I bought vs what I own
I'm just finishing up a major service:
Rebuilt air charge cooler
Disassemble and acid clean heat exchanger
Acid clean oil cooler
36 hour cycle of Evapo-Rust through exhaust manifold
Remove, clean and paint all plumbing
Replace hose couplings
Replace oil drain hose
Clean and paint motor
Oil and filter
New oil pressure switch
Two new batteries
Flush coolant from block and hot water heater
Attached are two pictures. One is the boat I bought, the other is the boat I own as I'm finishing up the maintenance.
A few things I learned:
Open the coolant drain valve on the low side of the block. Connect a hot water hose to the front of the block where the hose to water heater attaches. Turn on the hose and watch for several minutes while brown junk exits the valve. This was after draining all the coolant and it all was nice and clear green. So there was a bunch of brown slime coating the water passages in the block and head.
There is long, 1" diameter copper pipe that carries raw water from the heat exchanger to the exhaust manifold. It's about four feet long with several bends. The inside had hard black scale that looked like stalactites, crossing the inside of the tube.
The air charge cooler had a massive amount of scale on the raw water side and I believe this massively restricted the raw water flow.
The motor never overheated but the amount of scale that came out of the raw water circuit was several pounds. Makes me think that any flushing technique that doesn't involve disassembly is a waste of time.