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 !!!!
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.
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.
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.