Offroad-Express

Hey ORE, got a strange one here.

I have a small Isuzu in my boat and its overheating. Technically the boat is off road so i think we can fit it in here.

Its an old Isuzu 55hp marinised engine with a closed circuit cooling system. For some reason its been running a little warm of late.
My cruising speed is 1900 and anything above 1700 and it starts to creep up.

Can anyone spit ball ideas and things to check and maybe we'll come across the issue.
Already checked: thru hull fitting, sea strainer, impellor, heat exchanger, transmission oil heat exchanger,exhaust outlet water flow, and there is also shit loads of water flow out the exhaust so the motors getting plenty of water, so why shes heating I dunno????

cheers in advance

what about engine side, water pump and thermostat.

Thats what i was starting to think, but I have just had the pump reconditioned and was fine for the first few trips after. Im thinking thought that it could be the sender probe for the gauge.

I say this because there isnt any steam, and the water flowing out isn't that warm anyway so the coolant flowing in the exchanger cant be that hot, also when the gauge is reading 190- 200, the engine isnt actually that hot, I can nearly hold my hand on it so I actually dont think its really overheating. But Im skeptical to test that

What's the scale build up in the heat exchanger like ? If it is excessive it can serverly reduce the transfer of heat and allow hot coolant back to the engine .

UBZ wrote:What's the scale build up in the heat exchanger like ? If it is excessive it can serverly reduce the transfer of heat and allow hot coolant back to the engine .

I've just acid washed it and shes clean as a whistle in there. And like I said, we've got plenty of water flowing out the exhaust