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A Guide To Proper Seawater Plumbing

Go With The Flow

A guide to proper seawater plumbing.

We installed the Eskimo Ice Maker a few months before the air conditioner, but we handled most of the seawater plumbing at once.

The Contender was built for either inboards or outboards. Since this boat has twin outboards, it has lots of room for equipment, but the bilge where we had to work is tight. Fitting two seawater pumps, two strainers and two through-hull fittings in the bilge required careful planning. With that done, the job was easy.

Proper Seawater PlumbingPlumbing for seawater circuits is critical, though. Centrifugal air-conditioning pumps must be below the waterline to prime, and seawater hoses must rise continuously uphill from the through-hull fitting to the sea strainer and to the pump, and then continue uphill with a single high spot at the air conditioner.

The reason is simple but often misunderstood. Air conditioner pumps produce high flow once primed, but not much suction or pressure. Air pockets trapped in the hose before the pump keep it from drawing water to prime, and water trapped in low spots in the hose after the pump won’t let air vent overboard as the pump tries to push water through the hose.

Either will result in priming problems.

For the same reason, the hose from the discharge side of the air conditioner has to run smoothly downhill to the overboard discharge. Any dips that collect water might not let air escape when the pump turns on.

In the Contender, both air conditioner and Eskimo Ice Maker seawater pumps are above the waterline while the boat is on plane. A scoop over each through-hull fitting catches water and forces it to its pump. We chose a through-hull fitting with a separate scoop that is easily removed to allow proper prep and bottom paint, intentionally one size larger than required to catch more seawater.We installed the Eskimo Ice Maker a few months before the air conditioner, but we handled most of the seawater plumbing at once.

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