Cooling System Problem

[Guest]

We have a 1988 Catalina 30 with a Universal Diesel engine. After good sailing (over 5 knots and 20 degree heel) we lose prime in our sea water cooling system. This can be reprimed by removing the hose from the sea cock and filling it with water. The problem can be prevented by closing the sea cock when we are first under sail. I have checked the impeller and all fittings - all seems to be in order. Any ideas on what is causing the loss of prime and how to correct itother than closing the sea cock?

 

[Don]

Sounds like you have a leak.

The raw water pump is self priming. You should never have to prime it, unless it is sucking air somewhere. The impeller cover plate gasket (or seal) is the first place I would look.

 

[John]

Not a leak

Don,Thanks for the reply, but I have checked for leaks. Also this loss of prime only occurs under good sail and heel. It does not occur under light sailing conditions and does not occur if the boat is docked for an extended period of time.

 

[Don]

Cooling Problems

The lights just came on. Your c30 has the raw water intake on the port side of the hull, unlike my c27 that is centerline behind the keel. When you heel 20 degrees on a port tack, your intake could be out of the water and therefore loose its prime. Makes sense. Now, why won't it reprime itself? Mine will, even after draining the strainer, line and pump. IMHO, you have either a gasket that is too thick on the raw water pump, or an impeller that is too narrow. Hope this helps.

 

[Steve]

Sonds Funny...

I may be mistaken, but I find to VERY difficult to believe tha sailing at a 20 degree angle of heel would expose the sea water through hull. The problem here probably lies in some other direction.