Raw Water System

[JVS]

Has anyone run across this problem?  I have bubbles in the clear hoses between the heat exchanger and exhaust riser.  When I raise the engine rpm I lose the raw water all together and the engine will over heat..  I have been through the raw water system from the intake up and can't seem to find anything wrong..   It's a d2-55 volvo.  I'm pretty frustrated !!!!

[rangitoto]

Have you checked the intake vents on the sail drive. One of the owners here had a lot of tiny shells inside the sail drive housing which blocked the intake.

Another had oysters covering the vents.

Another cause could simply be the clamps at the seawater filter.

[JVS]

Thank you for your reply, but I've checked the vents, the impeller gear and all the hose connections.  I even wrapped the water intake valve with plastic wrap and duct tape to be sure it wasn't sucking air.  The only thing I haven't tried is back flushing the water intake at the sail drive, as the previous response suggested.

[Chrisstracey]

Hi

I had the same problem problem for about 6 months.  After looking at all the pipe work and pumps I  connected the raw water feed to the Head's Water intake as a test.  This proved that the problem was the leg water intake as water flow was good from the other supply

I cleared this by connecting  spare pressure pump to the intake and reverse pumping it.  This sorted out the water flow.