Just picked up a boat with a heater and never had a heater before. The water circulates through heater core at all times, correct? So if running antifreeze through engine, heater will be winterized too? ('08 raw water cooled Indmar MCX.) <BR> <BR>Gracias.

Yes but you want to get about 1500 RPM for 10 seconds or so to make sure. It takes a bit of pressure to circulate through the extra plumbing.

It should but I would drain it first and then how ever much antifreeze reaches the core will be undiluted. If little or none gets there, then no fear of freezing anyway.

Thx guys. That is very helpful.

I just disconnect the hose and blow the line out with a air hose to make sure.

don't count on it, I ran 5 gallons through my engine. spring came and i had a nice suprise.4 breaks in my core. disconnect and blow air through it after your done.

I agree with TigeMike and Steve. Drain that core first so you do not have to worry. The engine can suck up 5 gallons fast and the hoses to the heater core are very long and may not see all of the antifreeze.