Overheating Beta BD722

Habebty

Habebty

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I have a recurring problem with my engine overheating, I can't sustain more than 2700rpm(=4.8 knots) for more than 10 minutes. After an hours motoring today at 2700 rpm the alarm sounded.
There is a flow of water through the strainer
There is a new impellor
The heat exchanger has been cleaned,
and yet the problem persists over from the last couple of seasons.
The intake on the saildrive leg intake was been blanked off. and a separate seacock and strainer fitted.

I'm pretty certain the engine is getting hot and it is not just a sensor reacting early as the water from the calorifier is very hot.

When the alarm sounds I turn on the hot tap and get all the hot water out of the calorifier to help cool the cooling system and leave the engine on tickover so cold water is still coming into the system rather than let a hot block further heat the cooling system.

Can anyone suggest other things to check please as this is starting to irritate me now?

thanks
 
dont understand - if it overheats after 10 mins then how can you run it for an hour? and there is no way you can tell the engine is /is not overheating from the hot water system.

If your efforts with the hot water system work, it suggests that the problem is in your heat exchanger circuit. That has to be down to inadequate flow of water through the exchanger either because there is some blockage or because, for example, the pump is well worn. cannot give you a definite solution - you simply have tpo work through the circuit from input stop cock to outlet making sure everything is OK.

If the hot water routine doesnt reall work then the f irst thing to do since it should be quite cheap is to change the temperature sensor and also the thermostat.

after that diagnosis from the www becomes impossible. you need to get a mechanic to the boat.
 
[ QUOTE ]
dont understand - if it overheats after 10 mins then how can you run it for an hour?

[/ QUOTE ]
overheats after 10mins over 2700rpm (say 3000rpm)
overheats after 60mins at 2700rpm.
 
Have you cleaned the heat exchanger?It should be done once a year.Mine gets partially clogged with white residue and needs to be taken apart regularly.
Can you feel the exhaust water temperature?I have a telltale from the anti siphon device and when my alarm kept going off I could tell by the temperature of the water that it was the sender that was at fault.Replaced it and no more problems.The symptoms were the same as yours. ie overheating(or the alarm going off) after revving higher for a while.
 
You need to get an accurate reading of the freshwater circuit; borrow, hire or buy one of these and take measurements from as many parts of the cooling circuit as possible. It may be that the temp. sensor is just too low a temperature for the job.

Another possibility; inspect the exhaust hose and watertrap for internal collapse or blockage. Check the water injection elbow for blockage at the same time. The hose often collapses internally after being overheated by seawater pump impellor failure.

If the previous impellor disintegrated the bits may have lodged in the intercooler partially blocking the flow, but easy to miss when cleaning it out.
 
I had a similar problem when I was unfortunate enough to run a BD722. Tried all the fixes noted above without success. Tied alongside she could run full chat in gear without any problem but underway the little bugger would overheat at anything above about 2500rpm. Contacted Beta as it was a new installation (one year old) but all they could suggest was the fixes in the posts above. (boat NOT over propped)
Eventually changed the through hull fitting for one of the ones with a scoop - problem solved. Seems when moving through the water (5knts or so) there was enough of a venturi effect at the inlet to cause a reduction in flow through the pump/exchanger.
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hammer.gif
Artificial Intelligence is no match for Natural Stupidity.
 
I think that if you check the casting that forms the top of the thermostat housing and runs to the heat exchanger you may find it is occluded - possibly with casting sand.

This is the problem I had with similar symptoms to the ones you describe. Ran fine at 1400rpm but overheated at anything above 2000.

Photo before I removed the sand

[image]http://www.flickr.com/photos/landale_ge/3499915272/[/image]

And the sand I recovered from the casting

[image]http://www.flickr.com/photos/landale_ge/3499915738/in/set-72157617669514092/[/image]

/forums/images/graemlins/mad.gif for some reason I can't find the embedding urls on Flickr but the images are here
 
Mine is only 4 years old and has been like it from new. As it only overheated above 2700 rpm it never bothered me that much, but the overheat threshold does seem to be getting lower so will now investigate and try a scoop inlet.
 
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