Avoid Airlock Aggravation

Posted: February 1, 2013

By: Zuzana Prochazka

I have a 2012 Bayliner 225 SB, which is stored out of the water. Not long after turning on the AC, I noticed the cold air turned warm and the water discharge port was no longer discharging. There was an airlock in the pump that needed to be relieved by opening the pump intake hose. Can a “T” fitting be installed close to or at the pump to bleed the system to prevent this?
Airlocks are common problems on all kinds of pumps and even on gensets. It sounds like the AC pump is losing its prime when the boat is hauled and placed in the dry stack for storage, and then it is unable to reprime itself when launched. The first thing to check is the installation. The pump for an AC unit should be below the waterline, and the hose should make a straight and steady run up from the through-hull to the filter and then up to the pump. Upon launch, assuming the seacock is open and the through-hull, hose and filter aren’t clogged, the pump should self-prime automatically. If there are any kinks, bends or dips in the hose, air can become trapped and cause the pump to shut down.

If the installation is correct and it still doesn’t self-prime, you could install a valve between the filter and the pump. The procedure would then be to open the valve before starting the AC and letting a little water run through to clear any air. You could also bleed the air from the hose just by opening the filter and letting it fill up before turning the AC pump on. The closer the filter is installed to the pump, the better this would work. Frequently introducing air to systems that are designed to be kept filled with water (e.g., in a dry-stack situation) will cause airlocks, but there are easy and affordable solutions within reach.

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