Beta 20 running too cold?

graham

graham

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My Beta 20 in A 3 ton yacht runs cool at lower revs.

Did the thermostat in a saucepan check it starts opening at around 70 degrees C however the engine is only getting up to 65 degrees C at 2500 rpm .At 3200 rpm its on 80 degrees C .

I often use 2500 rpm or even 2000 rpm when motorsailing or gently motoring up the river to our mooring.
Is it something to concern about ?

I measured the cooling water coming out the exhaust at about 10 liters/minute Beta specify a minimum of 6.5 litres but dont specify a maximum. Its crossed my mind to try partially closing the seacock and watch the gauge possibly fit a restrictor in the intake pipe. The temp gauge agrees with my probe thermometer on the heat exchanger so I dont think the gauge or sender is faulty.

Any engineers with thoughts on it?
 
I think the volume of water taken in is determined by the pump, rather than the size of the intake pipe (unless the pipe was too small, not relevant to your case).
 
graham said:
My Beta 20 in A 3 ton yacht runs cool at lower revs.

Did the thermostat in a saucepan check it starts opening at around 70 degrees C however the engine is only getting up to 65 degrees C at 2500 rpm .At 3200 rpm its on 80 degrees C .

I often use 2500 rpm or even 2000 rpm when motorsailing or gently motoring up the river to our mooring.
Is it something to concern about ?

I measured the cooling water coming out the exhaust at about 10 liters/minute Beta specify a minimum of 6.5 litres but dont specify a maximum. Its crossed my mind to try partially closing the seacock and watch the gauge possibly fit a restrictor in the intake pipe. The temp gauge agrees with my probe thermometer on the heat exchanger so I dont think the gauge or sender is faulty.

Any engineers with thoughts on it?
Click to expand...

That sounds low...... especially as it is probably just starting to crack open at a lower temperature than you have observed
It should be marked with the temperature at which it should just start to open and also maybe at the temperature at which it should be fully open

I think I would check it again, heating it very slowly as you approach the opening temp. It helps to suspend it by a thread trapped under the flap. It'll drop as soon as it begins to open

( how are you measuring the temperature? I would use a mercury in glass laboratory thermometer but i realise not everybody has one)

I 'd probably replace it anyway

Restricting the cooling water flow is not a good idea because you will be reducing the flow through the exhaust and could overheat that if not careful or cause engine overheating if you increased the rpm without opening the seacock
 
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Do you have a calorifier and if so is the engine feed to it taken before or after the thermostat? When I installed my Beta 35 I modified it so that the calorifier is only supplied after the thermostat is open, in order that the engine doesn't run cold longer than necessary. I was told that the standard is to take the feed from in front of the thermostat so the calorifier is being fed as soon as the engine starts.
 
i have been using a digital probe thermometer its a high quality Rothenberg one so fairly confident in its accuracy.

I dont think changing the thermostat will make much difference as at lower revs the engine isnt getting up to the temp that the thermostat starts opening?

Dont have a calorifier.

Will check the thermostat again probably get a new one as a spare is good to have anyway.
 
Another alternative is that the engine is under-propped so it's not doing enough work to get hot. Does your prop have adjustable pitch, eg Featherstream or Kiwi?
 
The prop is a fixed 3 blade 13x9 which is standard for a Centaur with 20 hp. At full revs the boat is trying to exceed hull speed so I dont think its under propped.

Will try a new thermostat first and report back with success hopefully.
 
Years ago I had a Jaguar 27 with a 10hp Volvo MD1B. I wanted to put a 20hp Yanmar in but was advised that it would be overpowered and the engine would never work hard enough. 20hp in a Centaur is quite a lot.
 
Here is a spanner in the works.
I have a 40 hp diesel revving to 4400.
Rarely use more than 2500.
Have calorifier and hot air car heater before thermostat.
Sea water pump races round at high speed. Outlet is like a water jet , been like it for 37 yrs.
Engine has no trouble getting up to temp even with these factors that should make it harder.
Impellor is original. Replaced a rubber end cap on engine of heat exchanger recently as hose clip had cut through it. Saw inside and it was spotless!
Could a higher speed of impellor have some advantages ?
At 37 yrs it certainly does not appear to be running out of life !
 
Another explanation might be that the temperature sender on the engine is giving the wrong resistance values for the guage. This could be because it is not working properly or because it is a wrong sender/guage combination.

From memory, Beta used to fit Murphy gauges on their fancy instrument panels but fitted Murphy dual senders to all of their engines irrespective of what panel you purchased. So if an owner later added a VDO, or non-Murphy guage, the problem was that the resistance profile generated by the Murphy sender was different to what the non-Murphy guage was expecting and therefore gave wrong results.

Therefore before spending any money, I would suggest that you check the temperature that the engine is actually running at close to the location of the sender rather than the heat exchanger, as you have already tested. I wouldn’t be surprised to see the temperature at the exchanger quite a bit lower than at the sender, after all its purpose is to cool the circulating fluid.

Andy
 
I think the temp gauge is the most important engine instrument. Electronics ones on damp boats and me tend to be unreliable. I use a mechanical gauge which works off a fluid heating up. I don't know what this type is called but it's always on.
 
Rappey said:
Here is a spanner in the works.
I have a 40 hp diesel revving to 4400.
Rarely use more than 2500.
Have calorifier and hot air car heater before thermostat.
Sea water pump races round at high speed. Outlet is like a water jet , been like it for 37 yrs.
Engine has no trouble getting up to temp even with these factors that should make it harder.
Impellor is original. Replaced a rubber end cap on engine of heat exchanger recently as hose clip had cut through it. Saw inside and it was spotless!
Could a higher speed of impellor have some advantages ?
At 37 yrs it certainly does not appear to be running out of life !
Click to expand...
That’s a high speed diesel especially of for that vintage !
 
Tried Vic's truck ha going the stat by a piece of cotton.It started to open and fell off the cotton at 72 degrees C it is stamped 71 so seems to be operating perfectly.Then ran the boat underway and got following temps 2000rpm 65. 2800rpm70 3600rpm (maximum)85 will email beta these results and see what they say.
 
scottie said:
That’s a high speed diesel especially of for that vintage !
Click to expand...
It's actually 1965 and was in a morris A2 van , but was rebuilt for the boat in 1983.
It's what's commonly known as as bmc 1.5
The marine versions were restricted to 3000rpm.
There are many quoted hp and rpm . It seems quite hard to find facts when so many different "facts" are online ?
It certainly revs way more than amount needed to reach max hull speed.
40hp for ten tons.
 
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