2005 DF 250hp

[MikeMiami]

Recently, when trolling offshore at 2000rpm
and then place the throttle to neutral, the engine
temp light and buzzer goes On. The engine
seems to start overheating and as soon as I
start moving the boat forward, the engine temp
light goes Off and engine cools. The water from
the impeller shows Ok although not sure if is the
impeller. Any suggestions. Thank you.

[artdf175]

When was the last time the impeller replaced?
That should be done at least every two years
Another good spot to check would be the thermostat
Can give you a clue if there might be some corrosion you are not seeing elsewhere