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PeterI
PeterI

Posted: Mon Nov 14, 2016 7:22pm

Post Subject: Raw water cooling system

Hi, My BMC 1500 engined boat has a raw water cooling system. Raw water flows from sea cock with leaf filter, via Jabsco pump to the engine block, engine pump, exhaust cooler to pipe into exhaust. There is no filler cap on the exhaust cooler. There is a header tank, but again no filler. What is the purpose of the header tank without a filler? Does it need bleeding? How does it deal with silt in the engine block waterways? How do I winterise it - by draining it down fully, and re-lubricating the Jabsco pump each time I want to run it in the winter? The boat's documentation includes an invoice for anti-freeze. Is there a way of doing this without killing the fish in the canal? Thanks Pete

Raw water cooling system
Tony-B
Tony-B

Posted: Wed Nov 16, 2016 7:40am

Post Subject: Raw water cooling system

Something does not sound correct here but photos sent to the forum end up so small as to be useless so I need photos so I can see exactly what you are talking about. Please email some that show the whole engine, gearbox, and cooling system setup. You can email them via the magazine email address or for a fast reply direct to Tony@tb-training.co.uk. Thank you.

Tony-B
Tony-B

Posted: Wed Nov 16, 2016 8:13am

Post Subject: Raw water cooling system

I just realised that by combining your grease question with this one it might indicate that your engine is keel cooled with a wet exhaust but I still need photos to be sure. Please try to ensure I can see where the pipes and hose all run to. If it is keel cooled then my comments about the correctness of the pump I made in the grease topic would be wrong.

Tony-B
Tony-B

Posted: Fri Nov 18, 2016 8:50am

Post Subject: Raw water cooling system

I thought I had better give a fuller reply in case you wanted to do any work on the boat this weekend. The pump image supplied for the grease question is of the smallest pump fitted to BMC 1.5s. A direct raw water cooled engine uses one a size up while a raw water/heat exchanger engine uses one larger still. The talk of a header tank and antifreeze indicates that it is not a direct raw water cooled engine so with that small pump it looks very much as if it is a keel cooled boat with a wet exhaust. The pump is only to cool any gearbox oil cooler (if fitted), the exhaust manifold and the rubber exhaust hose. If I am correct the alternator belt will run over three pulleys rather than just two as on a direct raw water cooled engine. The image for this question is too small to see any detail. If I am correct in my assumption you will find two large cooling hoses that are the equivalent of a carâs top and bottom radiator hose running two a fitting in the bottom of the boat. The coolant passes through the fittings into tubes that are close to the hull where the surrounding water cools the content and the engine (car type) water pump circulates the coolant through the pipes. An explanation about cooling systems is here http://www.tb-training.co.uk/15cool.htm#bmn55 . To winterise it turn off the valve under the sea inlet, loosen the screws on the water pump back plate, remove the drain plug on any gearbox oil cooler and poke through it with a length of stiff wire to make sure the drain hole is free and finally do the same on the exhaust manifold. There will be no silt in the engine block because the raw water does not get into the engine. I may well change my mind about this if and when I get to see photos. I note that the engine is painted in Austin/BMC automotive green and not the typical silvery blue of the official marinisation so it was probably marinised by a small set-up so nothing can be assumed about what they have done. You should check/replace the rubber raw water impeller each year. If you take it out of the pump and as long as it is keel cooled you can run the engine for a very short time without any raw water. The limiting factor is how long it takes to set fire to the exhaust. The engine cooling itself will remain in operation. When you decide to drain the cooling system to renew the antifreeze you would clean all the oil form the bilge and engine drip tray. Then remove a low down hose from the keel cooler fitting and finally undo the block drain tap or remove the block drain plug and poke through to make sure it is clear. Then pump/sponge the coolant into a container for responsible disposal. Hopefully I can confirm all this if I get to see larger photos.

PeterI
PeterI

Posted: Sat Nov 19, 2016 6:26pm

Post Subject: Raw water cooling system

Tony, Thank you very much for your responses. I have sent you some photos. Thanks Pete

Tony-B
Tony-B

Posted: Sat Nov 19, 2016 8:00pm

Post Subject: Raw water cooling system

Pete has sent me a very full set of photos and a diagram. From these it looks very much like an armature marinisation unlike anything I have seen before. I have sent Pete a full reply but as it is an unusual setup it is only likely to confuse other reader. Especially as I can not post decent photos. If anyone has a specific need to know more then please email me. Once again this is nothing like the official and most other BMC cooling systems.

Tony-B
Tony-B

Posted: Sat Nov 19, 2016 8:02pm

Post Subject: Raw water cooling system

Spell checkers ******* - Armature should read amateur

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