Log in
Article search:

Q & A

Getting hot water a problem

I am having problems with the heating of the water from my engine to the calorifier! Sometimes it's getting hot but other times it isn't! Can anybody help with this please? Paulnderszo

Asked by: Paul Repton  | 6.25pm, Friday 16 March

WW says:

There are several possible reasons- the most likely is that there is an airlock in the pipework. This is most likely if the entry to the calorifier if higher than the exit pipework from the engine. You might be able to bleed air from the system by loosening the return pipework from the calorifier.
It is possible that the hoses have collapsed, but this is less likely.
Assuming that your engine is keel cooled, rather than freshwater cooled, you might be suffering from localised overheating of the engine, which can cause air bubbles to form, as the coolant degasses or boils. Check that the coolant has sufficient antifreeze in (33 to 50% concentration) using a antifreeze tester (a type of hydrometer- available cheeply from places like Halfords). Having the right antifreeze correct raises the boiling point to well over 100 deg C.
You may also want to check that the skin cooling tank has been bled- usually there is a screw to release trapped gasses.
If you let us know what engine you have, then we may be able to give more specific advice. Also, if a temperature gauge is fitted, what is it reading at normal engine running?
When the engine is hot, carefully run your hand along the calorifier coolant hose, starting at the engine and working towards the clarifier- a sudden drop in temperature often indicates an
air lock.
Let us know a bit more about your arrangement and engine and we maybe can be more specific.

Mark Langley  | 9.00PM, Friday 16 March

Beta suggests a header tank mounted, maximum 1 metre from the engine: the manual (downloadable from www.betamarine.co.uk) suggests carefully bleeding the circuit.
It might be worth checking the thermostat, although 75C isn't low, it might be that the coolant is circulating when it is not needed. It could be that the thermostat is stuck either partly or fully open and so causing some overcooling. The manual gives details on removal and testing of the thermostat and is a fairly easy task.
Most skin tanks have a small screw (often a small, 4mm cross-head) into the top of the keel tank, which a screwfriver will fit- or their might be a small bolt- or even a valve to vent gas out of the system; alas there is not set standard design!
It is sometimes possible to bleed gas out by loosening the clips on the pipe leading from the engine to keel tank (the hot water outlet)
Do you find that you have to often top up the header tank for the engine? if so, it might suggest gassing is occuring, or that the coolant is the wrong concentration.
I would also double check that the calorifier connections are also the right way round- that the outlet feed from the engine goes into the top fitting for the coil on the calorifier, and the return is the lower fitting, going back to the lower return feed on the engine. Sometimes boatbuilders do connect these the wrong way round; although it can be overcome when the engine is hot, it can impede circulation and so might cause poor heating at lower engine demands.
Ideally, the hose to the calorifier should fall from engine to calorifier, and be lower than the inlet (with no rises to trap air); then rise from calorifier return to engine- this way any gas bubbles will be expelled and circulation will be easier.

Mark Langley  | 12.05PM, Saturday 17 March

Readers say:

Thanks for your reply. The engine is a beta marine. The temp. Guage varies each time it is run. Obviously when it circulates it reaches 90/100. But when it doesn't only makes 75/80, it is keel cooled but I am not aware of a screw to bleed it. Where would that be? Cheers Paul

Paul Repton  | 10.11AM, Saturday 17 March

You must log in to post an answer.