Our sailboat has a very annoying (and sometimes dangerous) issue where the raw water
system will airlock downstream of the water
pump. I know it is downstream of the pump
because once the system is airlocked, nothing can be done to prime the system on the upstream side. The problem is prevented by closing the thruhull while sailing but this is unacceptable as a long term solution.
I've checked out this thread: air lock in raw water pump
, but most people there are talking about airlocks on the upstream side of the pump
My air lock happens when I sail in rough enough seas to allow air bubbles to accumulate in the system from the thru hull
. Once the engine
is started the air bubbles are pushed past the pump where it seems they can't get pushed past the anti siphon valve.
Here is my setup: 1986 Volvo
MD30 with heat exchanger
, engine oil
cooler and gear
cooler. The raw water
runs from the pump, to the oil
cooler, to the anti siphon valve then to the heat exchanger
after which a portion flows to the gear
cooler and back before it exits out the riser.
The only way I can prime the system is by removing the hose on the downstream side of the anti siphon valve and sucking on the hose with the engine running. I usually can't suck hard enough by mouth so a shopvac is required.
There must be something wrong but I can't imagine what. I have no leaks
, the pump and impeller are new with the correct size cam and the heat exchangers are free of debris.
Could there be something wrong with the anti siphon valve? I have a small hose attached to the air vent that redirects any leakage into the bilge
. I can blow and suck fine on the end of that hose so the valve is not clogged.