Optimax 150 overheat

[iainmartins]

I have an optimax 150 it overheats when i go above 2000 rpm. the tell tale looks ok any suggestions

[spence]

You should check (and replace) the thermostats first - are they opening?

[Turbodiesel]

Do you have water Pressure gauges on your boat? Check them if you do, Also when did it last have a water pump. The tell tale is not always a good indicator. The other thing is the pressure relief valve in the block if its not opening it wont let the water through properly.