Overheating at Idle

[Joe Kelley]

I have a 2003 Searay 220 Bravo drive 5.0 Mercrusier.
The moter overheated last summer because of impeller deterioration. Ran moter hot for appx 5 min 210degrees.

Replaced impeller, flushed, changed all fluids and filters, and replaced thermostat.
The engine overheats at idle and then cools down to 170 with acceleration.
Hoses to risers are cold. Air Pocket?
I have almost given up. Please help.

 

[Cincy Aquaholic]

My guess would be impeller pieces are causing blockage. Might need to back flush.

 

[Air O'Nautical]

Yes, I also think you have pieces of rubber in the system.
When an impeller breaks up the pieces have to flow down line.