Engine temperature problem...

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PetiteFleur

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I have a problem with my Beta 25 installed 8 years ago and has 650 hrs. Returning from Calais a few weeks ago I noticed that according to the temperature gauge the engine wqs running cool, barely moving from the start position. It usually runs at 80 C, but this was more like 40C. Fitted a new thermostat and today a new temperature sender. The temperature eventually got up to 55/60C but when engine slowed the temperature dropped down again.
The only thing changed just before the Calais trip was that I fitted a new calorifier, which works fine. Does anyone have any other ideas?
 
How large is the calorifier ? What throttle setting are you using, could be the calorifier is using all the available waste heat on even a moderate voyage.

I am also assuming you have vented all the air out.
 
The calorifier is the same size as before - 45 litres so should not make much difference. Venting air out? How do you do that? All I did was making sure the header tank was full and checked after running. Today I had the engine running at 3000 rpm for several minutes.
 
PetiteFleur said:
The calorifier is the same size as before - 45 litres so should not make much difference. Venting air out? How do you do that? All I did was making sure the header tank was full and checked after running. Today I had the engine running at 3000 rpm for several minutes.
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Assuming your run was with the engine in neutral the waste heat would be minimal , and 45 litres is a fair amount of water. Could be the system is air locked on the closed side (engine and cooling loop to the calorifier). Not familiar with the Beta engines but if the area around the thermostats is full of air then the coolant water might not circulate properly.

I would certainly look at a link between your recent works and current concern.
 
I would verify that the gauge itself is correct, easily done because at 40C you can hold your hand on the cylinder head indefinitely. I cannot think of any way in which the same water in the engine can heat the calorifier to its normal 60 - 70C or so but be at 40C in the engine.
 
On my new to me boat it ran cool due to a blocked heat exchanger, the flexible hose between the water pump and the heat exchanger collapsed as the pump tried its best to pull the water around..

Also noticed that once fixed it was impossible to get the engine up to working temperate unless it was put under load.

Engine also has a water bleed valve which you open once the circuit is sealed to allow any excess air out. Once water comes out you shut it.
 
Thanks for your replies everyone. Engine was under load, I motored up river for 20 minutes at 3000 rpm which was usually more than enough to get up to temperature. No water bleed valve fitted. The hose between the thermostat housing and heat exchanger is very short so no room for collapsing. All wiring has been checked and is ok.
I will check the heat exchanger next time I go to the boat as has been suggested their may be air around the thermostat housing and sender unit. Certainly when I replaced the sender unit no water came out when the old one removed. I'll also check the housing and hose.
 
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