A new client had mentioned that no mater how many times he changed his impeller on His Cummins Onan Marine Generator, the same fault code kept coming up. “Loss of Raw Water Flow”
It didn’t take us long to suggest that perhaps his heat exchanger might be blocked up, causing a flow restriction through the generator.
Our owner agreed to let us inspect it and yes, sure enough half the tubes inside the heat exchanger were blocked with calcium build up and the others were blocked by old pieces of nitrile impeller that the previous service agent had not checked for.
We removed the cooler from the boat and brought it back to the workshop for a service.
This fixed the problem and now our new client has a working generator again.
If your impeller comes out with missing fins, remember….they will still be inside the heat exchanger somewhere.