250cu, 165hp in-line 6 overheating !

[Silverline 1977]

1977 silverline 17ft . Wants to stay at 153 degrees @crusing speed 3000 to 4000 rpm, idel reaches 195 . Changed impeller thermostat engine only has 35 hours , took hose off stat housing only pushing 2” of water at idle, put 2nd hose on stat still when to 153 degrees . Could water circulation pump be bad ? Back plushed line to stat also.

 

[bondo]

1977 silverline 17ft . Wants to stay at 153 degrees @crusing speed 3000 to 4000 rpm, idel reaches 195 . Changed impeller thermostat engine only has 35 hours , took hose off stat housing only pushing 2” of water at idle, put 2nd hose on stat still when to 153 degrees . Could water circulation pump be bad ? Back plushed line to stat also.

Ayuh,..... Extremely doubtful,.....

Btw, tis is the Merc. Outboard forum,....
This should be posted in the Merc. I/ O forum,....