Winterizing a seawater cooled motor

[Charles Erwin]

We have a lot of advice about how to winterize heat exchanger (fresh water cooled) motors. For example, MaineSail has given excellent advice if your motor is equiped with a heat exchanger http://forums.catalina.sailboatowners.com/showthread.php?t=136339.

No so much for those who have seawater cooled motors.

Can someone give us the steps necessary to protect seawater cooled motors for winter?

Charles

 

[Rich Stidger]

When I used to have my Morgan 30 with an Atomic 4 raw water cooled engine, I winterized using the same basic steps with these exceptions.

I removed the thermostat first and I closed off the bypass connection so that the cooling water had to go through the engine block and then through the exhaust manifold. The A4, which may not be your engine, had a bypass that allowed cooling water to pass through the exhaust manifold while the block was allowed to climb to the operating temperature of the thermostat. Once the thermostat began to open the direct connection to the exhaust manifold was closed and the cooling water passed both the block and the manifold.

The rest of the steps are the same. I would run the engine and let it draw from a bucket of fresh water to flush the engine of any salt deposits. Then I would put antifreeze mix in the bucket and let the engine draw it in until it ran out of the exhaust. Be sure to run enough so that the water dilution in the engine doesn't raise the freezing point over your expected winter temperature. It has been recommended to test a sample of the antifreeze as it exits the engine to be sure you have adequate freeze protection.