Beta 20 overheat alarm

[alisdair4]

I have now had the same fault with my brand-new (less than 10 hrs) Beta 20 twice in 2 consecutive weekends. When starting the engine, it runs fine for about 20 minutes and then the overheat alarm sounds. When I stop the engine, it will restart immediately - I checked on both occasions that this happened to ensure that nothing had siezed. On both occasions however, I have left the engine to cool for about an hour, and then restarted it (having checked that there is coolant in the header tank). On both occasions, the engine has run perfectly.

I suspect that this has something to do with the thermostat opening as the engine heats up. Could the calorifier also be a factor - ie, could there be an air bubble in the coolant within the calorifier, which works its way through to the temperature sensor when the thermostat opens? As you can see, I am casting around from a position of little technical knowledge!

 

[pvb]

As it's a new engine, what do Beta say about it?

 

[alisdair4]

BETA 20

As it is a bank holiday weekend, I have not had a chance to speak to them. As I am currently mid-trip, I was merely trying to get an idea from other forumites if this was an unknown phenomenon!

 

[MoodySabre]

Sounds like a problem with the alarm setting. Does the engine actually overheat or can you keep going for a few more minutes and it then stops? It could be that the alarm is set just below the temperature at which the thermostat opens. You could try taking the thermostat out.

 

[TrueBlue]

I've got an older, bigger Beta in my boat and the overheat sensor has been rock solid for 12 years - not very helpful comment.
A calorifier pipe fell off last week amidst clouds of steam and the sensor obviously worked, again not much help.

It's probably not much help guessing what could be wrong, so best to ring Beta after the weekend.

Assuming there's no coolant loss (you said none) then possible causes could be:-

Faulty sensor
I didn't find a wiring diagram on the Beta site, so I guess the sensor is some form of heat sensitive resistor - these usually fail "off" so you shouldn't get it failing "on"
faulty sounder in control panel
The sounder relies on current passing through the sensor so the above applies
bad electrical connection
I've had bad connection in the plug and socket at the engine area, but that only affects charging and low oil pressure light
blocked area around sensor
Not really, as the engine metal around the sensor would conduct excess heat away.

Probably some other reason - but I'm stumped. In normal operation, the engine has to get above boiling point for the overheat sounder to operate.

They are very helpful at Quedgeley - though you may well have to wait while they nhelp other boaters. Might be an idea to aend them an email??

 

[VicS]

Is the raw water cooling flow Ok? bags of water coming ?

Difficult to expain what could be wrong with it that sorts itself out after the initial trouble though

 

[VicS]

I've got an older, bigger Beta in my boat and the overheat sensor has been rock solid for 12 years - not very helpful comment.
A calorifier pipe fell off last week amidst clouds of steam and the sensor obviously worked, again not much help.

It's probably not much help guessing what could be wrong, so best to ring Beta after the weekend.

Assuming there's no coolant loss (you said none) then possible causes could be:-

Faulty sensor
I didn't find a wiring diagram on the Beta site, so I guess the sensor is some form of heat sensitive resistor - these usually fail "off" so you shouldn't get it failing "on"
faulty sounder in control panel
The sounder relies on current passing through the sensor so the above applies
bad electrical connection
I've had bad connection in the plug and socket at the engine area, but that only affects charging and low oil pressure light
blocked area around sensor
Not really, as the engine metal around the sensor would conduct excess heat away.

Probably some other reason - but I'm stumped. In normal operation, the engine has to get above boiling point for the overheat sounder to operate.

They are very helpful at Quedgeley - though you may well have to wait while they nhelp other boaters. Might be an idea to aend them an email??

There is a wiring diagram in the owners manual thats on the website http://www.betamarine.co.uk/literature/operators manuals/1590-1025-HEKC-SOM-1011.pdf

I think you will find the sensor is a temperature sensitve "switch" . Could be faulty but does not explain why after the initial glitch it will run perfectly normally

 

[pvb]

As it is a bank holiday weekend, I have not had a chance to speak to them. As I am currently mid-trip, I was merely trying to get an idea from other forumites if this was an unknown phenomenon!

I think I'd have asked them a week ago after it first happened.

 

[Habebty]

My BD722 20hp is now 8 years old. When it was new it used to regularly overheat if pushed above 2900 rpm which would give me 5kts on a 5 tonne twin keel boat.
The raw water intake is a separate inlet on a seacock not the sail drive leg.

The Beta people weren't very helpful and builders were mystified. Whenever the alarm went off, I would run the hot tap to cool down the calorifier which in my mind works as an extra heat exchanger if cool water is pumped in from the tank!
Leave the engine running on tickover as long as water is still coming out of the exhaust to cool it.
In all instances, the correct amount of water was coming out of the exhaust as I measured it back in the marina. (see Beta manual)

Eventually I fitted a larger (bronze) skinfitting to allow a greater flow of water.

The original was 15mm dia. Which I changed to 22mm to match the inside dia of the pipe work.

Haven't had a problem since.

This assumes there are no blockages in your raw and fresh water cooling circuits and your temp sensor isn't on the wonk!

 

[AndrewB]

If a new engine overheats, there should be obvious signs, you can smell it for one thing, or see signs of steam etc. If you can't, then it's an instrument fault.

While a bubble can occur, normally it will be pumped clear when the engine is started, and if it was bad you might notice the coolant level has dropped a little. So I don't think this is likely.

The 20 min it takes before overheating provides a clue. A faulty thermostat failing to open could well cause the symptoms you describe. But I would first suspect a problem in the raw water system. Is a good flow of raw cooling water coming through? If the flow is slow it could be a damaged impellor or a blocked inlet. These are common, routine maintenance issues, and very easily fixed. Best not to run the engine until it has been done though, as it may result in bits getting drawn deep into the heat exchanger.

 

[CaptainBob]

Whenever the alarm went off, I would run the hot tap to cool down the calorifier which in my mind works as an extra heat exchanger if cool water is pumped in from the tank!

Good idea!

 

[alisdair4]

Cooling problems

Thanks, I will check this morning. There doesn't seem to be a systemic problem with the raw water, as the exhaust is always pumping out much more water than the old MD11c.
The hoses for the raw water were changed when the engine was renewed, so they should be OK. But clearly something ain't!

 

[stav]

I have some sympathy with you new engine and problems but you seem quite blase about looking after your new unit. Most people seem to have suggested sensible things to check. But if it was my boat and my engine I would be judging how hot the engine actually got then slecting to investigate the sensor or water side of things. Guess you need to be more scientific about the water coming out of the back can you catch it in a bucket and time how long it takes to fill?

Has the engine run underload for an extended time at all?
Is there some pressure in the hoses?
Could you take the temp sensor out and put a multimeter on it and dip it in boiling water and look for a change of resistance?
Trapped wire/loose connection?
Oil level?

Good luck with it but I might get an engineer to have a look if any of the above can not be done by yourself.

 

[TrueBlue]

There is a wiring diagram in the owners manual thats on the website http://www.betamarine.co.uk/literature/operators manuals/1590-1025-HEKC-SOM-1011.pdf

I think you will find the sensor is a temperature sensitive "switch" . Could be faulty but does not explain why after the initial glitch it will run perfectly normally

I'm obliged M'lud. Too lazy to search more thoroughly.

On a totally unrelated point - hasn't Beta's documentation improved by leaps and bounds over the years?? That manual has almost everything needed to even an anorak as I
Folks come onto these fora asking which (small) engine to buy. I would always lean (all other things being equal) to a product with lots of relevant documentation..

I'm now going to download the latest version for my engine!!

 

[TrueBlue]

I have some sympathy with you new engine and problems but you seem quite blase about looking after your new unit. Most people seem to have suggested sensible things to check. But if it was my boat and my engine I would be judging how hot the engine actually got then slecting to investigate the sensor or water side of things. Guess you need to be more scientific about the water coming out of the back can you catch it in a bucket and time how long it takes to fill?

Has the engine run underload for an extended time at all?
Is there some pressure in the hoses?
Could you take the temp sensor out and put a multimeter on it and dip it in boiling water and look for a change of resistance?
Trapped wire/loose connection?
Oil level?

Good luck with it but I might get an engineer to have a look if any of the above can not be done by yourself.

I read the original post as the problem went away after the second time the engine was started. Looking again it doesn't say that....

In my engine I find the heat exchanger wasn't terribly effective unless the header tank was always full to the top (then of course the excess would be expelled). In mine the tube matrix is near the top of the unit, which is not always covered by water...
No problems until I pushed the boat faster than Beta expected. Even so it never boiled, but got hotter than I would wish.

Worth looking to see if that might be the problem?

 

[nimrod1230]

On our previous boat the Beta engine would sound the overheat alarm if pushed hard. After some investigation of water flow/volumn etc the header tank/ exposed heat exchanger was identified as a potential problem. After fitting a remote header/expansion tank the engine could be pushed hard for extended periods without problems and the added bonus was being able to check the coolant level at a glance. Doesn't explain why this should occur but did offer a solution.

 

[VicS]

I read the original post as the problem went away after the second time the engine was started. Looking again it doesn't say that....

In my engine I find the heat exchanger wasn't terribly effective unless the header tank was always full to the top (then of course the excess would be expelled). In mine the tube matrix is near the top of the unit, which is not always covered by water...
No problems until I pushed the boat faster than Beta expected. Even so it never boiled, but got hotter than I would wish.

Worth looking to see if that might be the problem?

That is what I under stood by after an hour it restarted and "run perfectly."
I take "perfectly" to mean without overheating.

 

[alisdair4]

BLASE - ME?

I find it funny to be accused of being blase by Stav, when I think I was being the opposite by asking the question in the first place! The first time the problem occurred (last week) I suspected that I had not properly replaced the filler cap to the header tank after my daily checks (which would eliminate the oil-level option as a cause). This is cited in the Beta 20 Manual as one of several possible causes of overheating.

When the engine restarted, it ran without any problem for a further 5 hours last weekend. Thinking I had identified the problem as user error, I did not contact either Beta or an engineer.

Yesterday, while heading out to sea, the same symptoms occurred. This time, after it had cooled down, the engine ran (at almost full revs, as we were plugging into a nasty chop) perfectly again for about 2 hours.

This morning, I checked that the raw water system was OK,and that the impeller was intact. I then ran the engine at 1600-2000 RPM for an hour in an attempt to replicate the problem. Again, no issues, the engine ran perfectly, as did it when we returned to our berth tonight.

Next stop is to call Beta (who are not open on Bank Holiday weekends) as the engine is still under guarantee.

Thanks to all those who have provided helpful comment.

 

[donm]

I find it funny to be accused of being blase by Stav, when I think I was being the opposite by asking the question in the first place! The first time the problem occurred (last week) I suspected that I had not properly replaced the filler cap to the header tank after my daily checks (which would eliminate the oil-level option as a cause). This is cited in the Beta 20 Manual as one of several possible causes of overheating.

When the engine restarted, it ran without any problem for a further 5 hours last weekend. Thinking I had identified the problem as user error, I did not contact either Beta or an engineer.

Yesterday, while heading out to sea, the same symptoms occurred. This time, after it had cooled down, the engine ran (at almost full revs, as we were plugging into a nasty chop) perfectly again for about 2 hours.

This morning, I checked that the raw water system was OK,and that the impeller was intact. I then ran the engine at 1600-2000 RPM for an hour in an attempt to replicate the problem. Again, no issues, the engine ran perfectly, as did it when we returned to our berth tonight.

Next stop is to call Beta (who are not open on Bank Holiday weekends) as the engine is still under guarantee.

Thanks to all those who have provided helpful comment.

Just a thought, but I assume that you are using the correct coolant (and not water) in the sealed side of the system?

 

[alisdair4]

COOLANT

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?