Beta 20 overheat alarm

alisdair4 said:
Yes, the coolant is OK as far as I know- it was filled by the installer, who used a mix of water and anti-freeze. As a matter of interest, would this make a great difference? Presumably something to do with the different boiling points of water vs water with antifreeze?
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There are two reasons to use an antifreeze solution

One is that its protects the system from freezing.
The other is that the inhibitors in the antifreeze protect the system from corrosion.

As a heat transfer medium an antifreeze solution is not so good as plain water because it has a slightly lower specific heat. This difference is unlikely to be large enough to be problem and in any case the system is designed to be operated with an antifreeze solution as coolant

It is true that the antifreeze solution does have a slightly higher boiling point
 
A friend has a beta and every so often gets cooling issues especially when the engine is worked hard.
The problem was the engine annode which corroded in his case and dropped off into ghe water way and reducing flow and hence overheating.
Remove the rear housing to the annode to see if it has broken off. This might be the problem.
 
Anode corroded

I'll have a look, but I would think it less likely with a new engine - it was fitted in March, and the boat has been in since mid-Apr. Still, I guess stranger things have happened..!
 
The anode problem is a possibility although not vey likely in a new engine.I'd check the heat exchanger anyway.My own BD722 would set off the overheating alarm when worked hard until I fitted an expansion tank.That entirely cured the issue.I also replaced the sender.
 
A new Beta.... I had a similar problem with a 28bhp Beta and it turned out to be that the casting that sits on top of the thermostat was occluded by casting sand! - somebody hadn't checked when the engine was constructed!

Just undo the bolts that hold the casting onto the top of the thermostat and prod a screwdriver into it - I bet casting sand is what you find - clear that and the problem will go away.
 
If it was my boat, I'd

1. Pull the thermostat and check it in a pot of water, as well as check it for the crud mentioned earlier.

2. Check all the hose connections to the hot water heater, you may have a leak that stops as the water gets hotter and expands the hoses.

Do you have a temperature gauge or just an alarm buzzer?
 
alisdair4 said:
Hmm.! That isn't what I have experienced. Well, Beta are back at work tomorrow, we'll see!
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I found Beta and the installer very helpful - Beta where quite open about it and what may be the problem and to check the casting.

Hopefully they'll have the answer :-)
 
Of course you want to look into all the suggestions given so far, but over the years, there have been a number of threads about cooling, particularly with Beta engines and it may be significant. More modern, lighter diesel engines will heat up more quickly than their older relatives and a nominally adequate cooling system may occasionally prove inadequate. Your engine is not really run in yet, so may be generating extra heat which will be enough to sound the alarm. I think every thread touching on this subject has had one contributor who has increased the internal diameter of the seacock and cured the problem. When I last looked at engines, I was surprised how few gave the cooling water requirement in the manual - its not insignificant to remedy: haul out, change seacock, new hoses... Others may be able to quote the effective diameter of different types of seacock, but many are much smaller than you would think. Better to use a size larger and then fit the hose barb to suit. Most manufacturers are very quiet about the internals of their seacocks.

Rob.
 
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