Three-Way Valve for Engine Sea Water Intake - SailNet Community
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post #1 of 5 Old 11-07-2008 Thread Starter
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Three-Way Valve for Engine Sea Water Intake

I am sure that someone has thought of this before, but anyone here install a three-way valve as the primary shut-off seacock for sea water intake for engine coolant?

Why would anyone want to do this you may ask? I was thinking of doing to make it easier to winterize my motor. The three way is a T configuration that has valve that directs the primary flow to either one side of the T or the other depending on on which way the valve is turned. I would install the valve and plug cap one of the T sides and connect the other T side to the impeller pump/motor. Under normal operation, the valve would be turned in that direction. When I want to shut the water flow to the motor, I'd flip the lever to the other T side, which is plug capped so it won't leak.

To winterize the motor, I'd remove the plug cap and connect a nipple w/hose tube to the valve. Put the other end of the hose into a bucket of Antifreeze and then flip the valve to the open the flow that way.

The benefits, as I see it is that I never have to remove a hose from the sea water system to put in anti-freeze. This is a pain as my hoses are REALLY tight on my fittings. The down side is that the valve is never truly closed to the sea. The seal is the cap plug.


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post #2 of 5 Old 11-07-2008
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Interesting idea...or one could leave the thru-hull valve alone and just install a T between the valve and the pump with your capped hose attached. That way there's never any mistake involving turning the three way valve to the wrong position and you have a valve that you can close and your antifreeze hose ready to go as well.

S.V. Nikko
1983 Fraser 41
La Conner, WA

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post #3 of 5 Old 11-07-2008
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Pull the hose from the downstream side of the sea strainer. No need to fill the sea strainer with antifreeze, you can drain it or suck it dry separately.
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post #4 of 5 Old 11-07-2008
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You don't need

You are over thinking it. You don't need a multi-position valve. I don't think you'll have much luck finding a bronze multi-position, UL Marine listed valve for use bellow the waterline anyway.

The easy way is to just add a tee to the input of the sea strainer. From here you can winterize.

Once the tee is installed you can then plug the winterizing port with a plug. When you need to winterize close seacock, remove plug and insert hose and barb and suck the antifreeze through.

P.S. It takes me all of 30 seconds to remove the hose from my sea strainer and connect my longer winterizing hose.

-Maine Sail / CS-36T

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Last edited by Maine Sail; 11-07-2008 at 10:28 PM.
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post #5 of 5 Old 11-07-2008
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Yup - what Maine Sail said! Will work just fine and is quick and easy.
OR .... you could just do what I did: Move your boat into the tropics so you never need to worry about antifreeze! (Heh-Heh!!)

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