testing the temperature sender?

[PetiteFleur]

Engine appears to be running cool, it's normally at 75/80 degrees C. Beta 25hp - 8yrs old. Fitted new thermostat today but still no joy. The engine is obviously working ok as the calorifier gets the water hot. Is there any way to test the temperature sender without replacing it? The gauge is by Murphy.

 

[prv]

Unscrew it from the engine and drop into a saucepan on the stove? Maybe bend up a little wire frame to hold the outside part out of the water if it doesn't look too waterproof.

Pete

 

[nigelmercier]

Unscrew it from the engine and drop into a saucepan on the stove? ...

... And measure the resistance at different temperatures. Then find out what they should be.

 

[earlybird]

Leave the sender in place to begin with. Remove the wire and measure resistance from terminal to ground.
My B25 manual says ~3.5kohm cold; 0.5 kohm warm.

 

[PetiteFleur]

Thanks everyone, will go to the boat tomorrow and try suggestions

 

[DaveS]

Agree with all of the above. Another idea is to point an IR thermometer at the outside of the engine to check for agreement with the gauge. These are now cheap enough (Chinese, ebay) to justify keeping one on board.

 

[VicMallows]

Another idea is to point an IR thermometer at the outside of the engine to check for agreement with the gauge.

Or even a a basic thermocouple thermometer (or even cheaper thermistor one) held tightly against the water jacket.

 

[DaveS]

Or even a a basic thermocouple thermometer (or even cheaper thermistor one) held tightly against the water jacket.

Indeed. One advantage of an IR thermometer is less chance of getting something caught in a moving belt.

 

[nigelmercier]

One advantage of an IR thermometer is less chance of getting something caught in a moving belt.

Vital bit of kit in my view, for under a tenner: http://amzn.to/1pL7bat

 

[Petronella]

We had a similar problem and I also tried replacing the thermostat (which was a tricky job). In the end it turned out to be a loose connection on the back of the gauge. May not be your problem but very easy to check.

 

[Sailingsaves]

Vital bit of kit in my view, for under a tenner: http://amzn.to/1pL7bat

That is so cheap it seems incredible.

Just ordered one. If it works it will be useful for so many jobs.

Us (as in me, not USA) inventors don't stand a chance when kit like that can be knocked out so cheaply.