Hi there, Universal diesel problems. I guess I'll just start from the beginning...this is the M3-20, 18 horse, 3 cylinder. Never had a problem, has 2000 hours on it. I ran over a huge fishing net, not around the prop but dragging on the rudder for 2-3 minutes...overheated engine. I put water in reservoir, overheated next day. Checked raw water strainer, it's fine. Pulled impeller, it's fine, water pump is new, check oil..it's fine, not milky head gasket seems ok, pulled thermostat, boiled it, it's fine, put new one in anyway. Next day, ran 24 hours at 2500 rpm, works fine, rev down to 1300 while anchoring...overheats. Pull thermostat all together, pull heat exchanger to look for crap, pull all hoses to look for crap, pull hoses off hot water heater and bypass it in case it's clogged, dove on thru-hull to look for crap, no problems evident anywhere. Checked fresh water pump for play, discolor, noises, pulled it off, looks like new.
