I'm having a problem with a merc 496. After an impeller change I could only get one side of the exhaust to flow water. I back flushed the whole system piece by piece. I'm tinking its the check valves on the manifolds. Any information would be great.

there is a ckeckvalve on the inlet side of both manifolds-take them apart and I am pretty sure you will find some salt build up in that area-

thats what i thought. Do they just pop apart or are they threaded? The 496 is still new to me.

the boat ran aground too.

I hooked the hose directly to the manifold and it stayed cool. The heat exchanger is clear. I just don't understand the whole raw water system.