Beta Marine 3-Cylinder Engine BD722 Operating Temperature?

CaptainBob

CaptainBob

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My car (Suzuki Swift 3 cylinder) always shows the exact same temperature on the guage once warmed up - I guess due to its thermostat... my BD722 seems to run at a temperature which depends upon how hard it's working. Seems to be about 80C when running for a long time at about 2000rpm, but is nearer 90C when running long term at 2700rpm. Because of this I've not run it at it's supposed working rpm of 3000 for any length of time.

Manual says nothing about a thermostat so am I right in thinking that this variation is OK and to be expected? Or should the increased flow rate of seawater with increased rpm make it hold one temperature? I'm guessing not because the seawater temperature varies.

Many thanks!
 
I have a BD622, same engine as 722, and there is some variation with load but not a great deal. Up to 95-100 deg. C. should be acceptable, the pressure cap equates to about 120 deg. Another factor is that the gauge is unlikely to be very accurate. I'm fairly sure there was a thermostat in mine when I looked a while ago.
PS make sure the antifreeze is up to strength for the higher temps.
 
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Mine is like that and at 6 years of age no problems.I don't have a worry gauge,I can feel the exhaust water temperature from the anti siphon telltale and it's always lukewarm.
 
It depends where the temperature sensor is located in the cooling circuit. In my wife's Smart roadster, the temp out of the heater is nice and warm before the temp needle moves off its stop. In my Lotus, the temp varies from 88 deg to 100 depending on how much I'm enjoying myself driving it.

Wouldnt worry. Thrash the engine and see what the temp gets to. As long as its below about 100 C then you're OK.
 
Interesting - I also have the 3 cyl Beta, 25HP(not sure whether it's the 722) and I had a similar incident a few weeks ago. I was running the engine at 3000 rpm as I was trying to cheat the tide a bit and after ½ hr the temperature alarm went off! The gauge read 100º C so I shut the negine down and checked water, oil etc etc. After it cooled down it started OK and had no problem since but I'm keeping a close look at the gauge more often. It seems to be OK at up to 2500 rpm staying at a steady 80ºC, when I increase the speed the temperature goes up.
Even though there is a good sea water flow when running, I intend to check the thermostat, impellor and change the coolant this winter.
 
M33 said:
Interesting - I also have the 3 cyl Beta, 25HP(not sure whether it's the 722) and I had a similar incident a few weeks ago. I was running the engine at 3000 rpm as I was trying to cheat the tide a bit and after ½ hr the temperature alarm went off! The gauge read 100º C so I shut the negine down and checked water, oil etc etc. After it cooled down it started OK and had no problem since but I'm keeping a close look at the gauge more often. It seems to be OK at up to 2500 rpm staying at a steady 80ºC, when I increase the speed the temperature goes up.
Even though there is a good sea water flow when running, I intend to check the thermostat, impellor and change the coolant this winter.
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These engines are prone to mild overheating and in my opinion they would benefit from a bigger more efficient heat exchanger.
 
I would love to hear about any resolution to the temp problems with BD722s as this is driving me mad now.

Heat exchanger is clean
New impellor
coolant mix is right
Raw water strainer clean
Thermostat ok
hull is clean
prop is clean and matched to the boat/engine

When I get the time I will check the amount of water pumped through the system as stated in the Beta manual, but visually there is a good flow so I suspect this will be within spec.

I can run all day at any engine speed up to 2300rpm but this only gives me 4-4.2knots. I can only run at 2800-3000 rpm (5 knots) for about 10-20 minutes before the overheat alrm sounds.

I can only assume the heat exchanger does not have a big enough surface area to cool the freshwater as the engine speed increases.

Any other thoughts anyone?
 
wherry said:
I can run all day at any engine speed up to 2300rpm but this only gives me 4-4.2knots. I can only run at 2800-3000 rpm (5 knots) for about 10-20 minutes before the overheat alrm sounds.
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Exactly that and it's done it from new! always have to check the system though so very annoying.. I open the engine compartment door and this helps at high rev's, sometimes think it's the compartment ambient temperature that causes it but know this cant be true. One day I will get round to fitting a gauge to confirm the alarm is not activating at a to lower temperature.. nothing seems to hot when it goes off!
 
I can't remember the Beta installation. It will have a seperate salt water pump. Fitting a slightly smaller pulley will increace the output and thus reduce the temperature. Altermatively you could fit a higher delivery pump. Don't go mad as there's a correlation between pump flow rate and max pressure and you don't want to blow the seals on the heat exchanger.
 
wherry said:
I would love to hear about any resolution to the temp problems with BD722s as this is driving me mad now.

Heat exchanger is clean
New impellor
coolant mix is right
Raw water strainer clean
Thermostat ok
hull is clean
prop is clean and matched to the boat/engine.....

....I can run all day at any engine speed up to 2300rpm but this only gives me 4-4.2knots. I can only run at 2800-3000 rpm (5 knots) for about 10-20 minutes before the overheat alrm sounds......

Any other thoughts anyone?
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This is all very familiar! I had exactly the same experience with the same engine, for two years.
When absolutely everything was verified correct, I turned to the last possible cause: venturi-effect at the raw-water intake 'sucking' and therefore opposing the suction of the raw-water pump.
Three years ago I replaced the inlet fitting with a larger one with larger hoses all the way to the inlet strainer, which is within the engine bay and very close the the pump.
Result? No more overheat problems! (As long as remember to open the seacock!)
 
wherry said:
I would love to hear about any resolution to the temp problems with BD722s as this is driving me mad now.

Heat exchanger is clean
New impellor
coolant mix is right
Raw water strainer clean
Thermostat ok
hull is clean
prop is clean and matched to the boat/engine

When I get the time I will check the amount of water pumped through the system as stated in the Beta manual, but visually there is a good flow so I suspect this will be within spec.

I can run all day at any engine speed up to 2300rpm but this only gives me 4-4.2knots. I can only run at 2800-3000 rpm (5 knots) for about 10-20 minutes before the overheat alrm sounds.

I can only assume the heat exchanger does not have a big enough surface area to cool the freshwater as the engine speed increases.

Any other thoughts anyone?
Click to expand...
I had the exactly same symptoms last year.The alarm would go off after a while at higher revs.Exhaust water temperature still lukewarm.In the end got a different temperature sender,the standard Kubota one with just one connection for a buzzer,and it's all good again.I also increased the size of the inlet seacock to 1" but that was years ago.
 
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