running hot

[farmer brown]

so I finally get my boat back in the river and its running hot. Iv put a new temp gauge in, replaced thermostat new sender pulled waterpump off  everything looks fine flushed out all lines and cooling system and am at a bit of a loss as too whats going on. temp gauge stops at 250F about 120C it climbs up to that quite quick its got a closed cooling system and boats running a v3000 motor. It never had a temp gauge before and I never noticed that it ran overly hot anyone have any ideas on were I could go from here

[rogee]

Test your new thermostat to see it actually opens   , beware the Chinese crap ones

[farmer brown]

ended up just taking it out and still ran hot even after I parked up for 2hrs and let temp settle back to acceptable levels

[Nigel]

is it raw water cooled or heat exchanger?

[farmer brown]

is it raw water cooled or heat exchanger?
heat exchanger

[johnmead]

What sort of heat exchanger? Tubes blocked by little stones? Not enough cold water going through --- blocked pipe out of unit?

[farmer brown]

What sort of heat exchanger? Tubes blocked by little stones? Not enough cold water going through --- blocked pipe out of unit?

home made copper exchanger have flushed all system and seems to be fine have taken outlet hose off whilst running boat and seems to be pumping water thru whole system fine im going to plumb onto a decent pressure water system and run moter and see what happens what temp should I safely be running and at what temp should I get woried

[Spanners]

Whats your Delta T on both sides of the cooler?

[farmer brown]

Whats your Delta T on both sides of the cooler?

sorry don't understand what your asking

[mohawk]

If its a tube in tube under floor exchanger make sure the cooling water and engine water are moving in opposite directions.

[mohawk]

sorry don't understand what your asking

x2 

[stu#71]

I'd start with the basics. Test your sender against the gauge in a jug of hot water. Is it actually reading correctly against a thermometer in the jug?

[Spanners]

Differential temp of the cooling water and the engine water.
Inlet and outlet temp of each side of the cooler

[farmer brown]

I'd start with the basics. Test your sender against the gauge in a jug of hot water. Is it actually reading correctly against a thermometer in the jug?

ok good advise establishing a true reading makes sence to start with. mite be busy next few nights so I can go boating in weekend keep the advise coming im having boating withdrawls already I even had arvo off today weather turned out perfect for a hunt but dogs stayed in there kennels whilst I pulled my water pump and cooling system to bits and theres pigs living just behind my house I must be going mad

[Spargs]

How are you getting on?