Is Our BMC Raw Water Cooled

[DandGNWales]

I had a quick look at our boats water cooling system, it seems to have a form of large upright approx 6 inch square tank that you can take the top off and it is mounted verticaly in the engine bay, it also has what looks like a header tank with the usual radiator cap and when the engine is running it pumps water out of the exhaust, so is our engine canal water cooled ?

 

If so how do I winterize it and do you need an antifreeze mix in the header tank?

 

I will try and get some good pix when down with her again next week but any help would be great

[RLWP]

We really need pictures. There is a good chance you have a cooling system that has an enclosed circuit which is itself raw water cooled. Have a search around to see how many water pumps you have

 

Richard

[DandGNWales]

Hi Richard,

Thanks for your reply, I have done a bit of web searching and I think I have a skin tank system, as the diagram I found for a skin tank system also cooled the gearbox, just like it does in ours, so if ours is skin tanked how often to you clean out the mud box ?

 

I will take some pictures, we have been just using our phones but need a flash to get a good pic then will let you guys fill me in, as I'm starting to panic for the winter lay up

[Robbo]

Skin tanks don't need mud boxes

[RLWP]

Hi Richard,

Thanks for your reply, I have done a bit of web searching and I think I have a skin tank system, as the diagram I found for a skin tank system also cooled the gearbox, just like it does in ours, so if ours is skin tanked how often to you clean out the mud box ?

 

I will take some pictures, we have been just using our phones but need a flash to get a good pic then will let you guys fill me in, as I'm starting to panic for the winter lay up

 

The gearbox cooler isn't enough to eliminate raw water cooling. As Robbo says, skin tanks don't have a mud box, but a two circuit system would

 

Richard

[Tony Brooks]

That description sounds rather like some heat exchanger cooling systems I have seen on older boats. The header tank on the engine is the heat exchanger while the square box (mounted on the swim/uxter plate?) is a header tank for the skin tank system. The way to tell is to see if it has a pulley driven engine water pump plus a brass rubber impeller (Jabsco) "raw" water pump - plus photos. We will need to see all around the engine so we can trace pipework and look for pumps.

[The Bagdad Boatman (waits)]

If water pumps out of the exhaust then you have a raw water cooling system with a heat exchanger. The inlet of the mud box is at the bottom and should have some sort of weed filter with a valve/tap to stop the the inlet. By closing the inlet and running the engine until the exhaust stops spitting out water the raw water system is winterised. Put antifreeze into the header tank for the heat exchange part. When you run the engine you tell if there is any weed blocking the raw water inlet by the sound of the exhaust.

[DandGNWales]

Thanks again for your replies, I will get busy with the camera, there is a pump driven by the crank pully then another pully driving the alternator, will update with pix when back on board

[Tony Brooks]

If there is only one pump and it is positioned and looks like an older car water pump then it is almost certainly skin tank or keel cooled.

[Dalslandia]

If it is raw water coöled, it use raw water, that come out in the exhaust or hull side.

others it is boiled water cooled, so if it is boiled it is not raw? :-)

 

any way, there is several options.

raw water from outside goes into engine and out, somewhere. see above.

raw water goes into a heat excange, that cool the closed circut water in the engine, the raw water often then cool gearbox oil cooler, and the exhaust pipe/hose

the internal water cool the engine oil.and the exhaust manifolder

 

Keel cooled

if it is dry exhaust, the internal pump is used to circulate water in the engine and when thermostat open it circulate out to the skin tank.

 

dry exhaust and heat exchanger, the "raw" water goes to the skin tank and back to the heat exchange

 

Having the engine conected to the skin tank and use raw water from out side to cool oil cooler and exhaust seems dumb.

Edited October 4, 2013 by Dalslandia

[RLWP]

Having the engine conected to the skin tank and use raw water from out side to cool oil cooler and exhaust seems dumb.

 

Some installations of the BMC 1.5 have a closed circuit running through the engine and gearbox cooler, with a heat exchanger in the header tank. There is then a raw water circuit that passes through the heat exchanger and out the exhaust

 

Without seeing photos I'm hesitant to identify exactly what the OP has

 

Richard

[DandGNWales]

Well just to update the post, had the marine engineer in today and as thought our baby is raw water cooled, so my next question is how often do you clean the mud box out ?

[Tony Brooks]

 

Well just to update the post, had the marine engineer in today and as thought our baby is raw water cooled, so my next question is how often do you clean the mud box out ?

Unless you want to confuse in the future you really need to sort this out. IF you have a car type water pump as you said earlier then it is not direct raw water cooled but has two circuits. Again IF you have a car water pump you should also have a brass raw water pump because it is indirect raw water or heat exchanger cooled. I not that you did not supply the photos as asked so we can still not see which you have.

 

Unless you resolve this you will be in the hands of the engineer because you will get confusing advice from here - people will advise for the wrong type of system.

 

As far as the mud box is concerned the answer is "when it needs it" and that depends upon the water you are boating on/through. On some shallow and very weedy waters it could be several times a day on deep clean rivers it could be days or weeks between cleaning. Basically keep an eye on the raw water discharge and if it reduces clean the mud box. If it is easy to do then look every day. However reduced raw water flow can also be problems with the raw water pump, blocked heat exchangers/oil coolers and hoses. This is why you need to really understand your system.

[DandGNWales]

 

 

Unless you want to confuse in the future you really need to sort this out. IF you have a car type water pump as you said earlier then it is not direct raw water cooled but has two circuits. Again IF you have a car water pump you should also have a brass raw water pump because it is indirect raw water or heat exchanger cooled. I not that you did not supply the photos as asked so we can still not see which you have.

 

Unless you resolve this you will be in the hands of the engineer because you will get confusing advice from here - people will advise for the wrong type of system.

 

As far as the mud box is concerned the answer is "when it needs it" and that depends upon the water you are boating on/through. On some shallow and very weedy waters it could be several times a day on deep clean rivers it could be days or weeks between cleaning. Basically keep an eye on the raw water discharge and if it reduces clean the mud box. If it is easy to do then look every day. However reduced raw water flow can also be problems with the raw water pump, blocked heat exchangers/oil coolers and hoses. This is why you need to really understand your system.

Hi Tony,

Thanks for your reply, the marine Engineer was very busy so just told me it is canal water cooled and also has a tank with antifreeze for the heat exchanger. I only have my camera phone and as it is very murky here and does not have a flash I don't think the pictures would be of any value, but once I find my proper camera, I will take some pictures to finally know 100% what we have.

 

It was my confusion, the water pump is a big brass type run from a separate belt to the alternator, and from looking the engine also has a normal car type water pump that flows the water/antifreeze mix around the system.

 

I am taking her up the river later, so when I have the engine covers up will give the camera phone a go and see how they turn out, thanks again for your help, I do really want to bottom this out.

Cheers

Geoff

[mrsmelly]

Hi

 

Im a bit laet on this one but you could well have both systems. Two of our engines at work are raw water cooled and keel cooled at the same time. This is unusual but works very well, our engines do a hell of a lot of hours without problem.

 

Tim

[Tony Brooks]

Allowing for the possibility that it is an odd one like Tim describes I feel it is almost certainly Heat exchanger/ indirect raw water cooled.

 

You need to get to grips with changing the raw water pump impeller (the brass one), cleaning heat exchanger tubes and eventually descaling the exhaust mixing elbow.

 

Glad we have got it more or less sorted.

[Naughty Cal]

Our boat is also indirectly raw water cooled and it is a very effective system. You will need to learn how to change the impellor though, even a short term raw water restriction will pull teeth off the impellor.

 

Also you will need to protect your raw water system during the winter from frost damage.

[nebulae]

When winterising your engine,turn off the valve on the mudbox/filter. Run the engine until water stops coming out of the exhaust(max,a couple of minutes)There may be a water trap on the exhaust(This stops water running back into the engine)If so,it will usualy have a drain on the bottom.Make sure that the direct cooling system has at least 25% antifreeze .DO NOT run the engine for long periods without antifreeze/corrosion inhibitor in the direct cooling system.Allways carry a spare impellor for the Jasco type pump.I recommend that you turn off the seacock when you are not running the engine,otherwise,if a pipe comes off,the boat will sink.

[Naughty Cal]

When winterising your engine,turn off the valve on the mudbox/filter. Run the engine until water stops coming out of the exhaust(max,a couple of minutes)There may be a water trap on the exhaust(This stops water running back into the engine)If so,it will usualy have a drain on the bottom.Make sure that the direct cooling system has at least 25% antifreeze .DO NOT run the engine for long periods without antifreeze/corrosion inhibitor in the direct cooling system.Allways carry a spare impellor for the Jasco type pump.I recommend that you turn off the seacock when you are not running the engine,otherwise,if a pipe comes off,the boat will sink.

Alternatively if you have access to a reliable electric supply keep the engine bay heated. This is what we do and it also means we can still use the boat without a load of faffing about each time.

[Neil2]

When winterising your engine,turn off the valve on the mudbox/filter. Run the engine until water stops coming out of the exhaust(max,a couple of minutes)There may be a water trap on the exhaust(This stops water running back into the engine)If so,it will usualy have a drain on the bottom.Make sure that the direct cooling system has at least 25% antifreeze .DO NOT run the engine for long periods without antifreeze/corrosion inhibitor in the direct cooling system.Allways carry a spare impellor for the Jasco type pump.I recommend that you turn off the seacock when you are not running the engine,otherwise,if a pipe comes off,the boat will sink.

I don't think you can ever be sure there will be no water in the raw water part of the system.

 

I recently hired a raw water cooled boat and asked the guys at the yard how they winterised them. They close the seacock and take the top off the filter/mud box then turn the engine over whilst pouring a 50/50 anti freeze mixture into the filter/mud box. Someone has to watch the exhaust until coloured water starts coming through, ideally with a bucket to stop any discharge into the canal, though you can use environmentally friendly anti freeze as a further precaution.