SeaRay 290 7.4 Mercruiser gets hot if not idling

[harmony]

I have changed the water pump, thermostat, impeller, and checked hoses with 90 degree angles but the boat runs hot when RPM is increased from idle. Don't know what to do next.

 

[jason78]

Could be a RAW water flow restriction causing low pressure. Did you change the circulating pump or the RAW water pump? The water inlet on the transom assembly has been known to corrode and cause blockages. What kind of drive? Bravo? Is the boat slipped?

 

[mvoellinger]

Check manifolds/risers/elbows. If they are corroded they can restrict water flow.

 

[LG111]

Pull the caps off the heat exchanger and run a hanger thru each port.