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Thermostat for BMC 1500


Mad Harold
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My boat has direct raw water cooling and when I bought it I noticed the temperature needle hardly moved off it's stop.On investigating I found that there was no thermostat fitted.I fitted an 82 degree thermostat and now the engine runs at 80 degrees.

I have posted on another thread and was advised [by Mr. Brooks] that this is too hot for a direct raw water cooled engine,but ok for a heat exchanger cooled engine. I can only think that this is because with a heat exchanger cooled engine the cooling water entering the engine will already be hot,but with direct raw water cooling it will be cold causing a thermal shock.  Is this a correct assumption to make?

There is a 74 degree thermostat listed by ASAP supplies,but I am not sure if 8 degrees will make much difference to the chances of a cracked cylinder head.

Would I be better off running without a thermostat ? as the boat was when I bought it.

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I don't think thermal shock is the problem,: the water will be coming passing through the engine from the time it is started. At higher temperatures, corrosion may be increased, and also the deposition of anything dissolved in the cooling water. The obvious one is salt in a sea going boat :D , and recommended raw water cooled temperatures seem to be based on salt water use. 

The highest coolant temperature may not be at the thermostat, so a higher running temperature may cause the possibility of local boiling, as a direct raw water cooled engine does not have a pressurised cooling system. The difference between highest and thermostat temperatures would increase as the engine is worked harder.

A thermostat is an improvement over none, as without one a cold engine may never warm up in low temperatures, and a cold engine will wear faster than a warm one.

 

 

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No - its nothing to do with thermal shock unless you restart a badly overheated engine without allowing it to cool properly.

I will explain again (as per the other thread and what others said there). Once the water temperature gets much above about 60C and solids dissolved in the water start to come out as per the scaling in a kettle. That is fact. The hotter the water the more scaling.

A heat exchanger boat keeps the same coolant in the engine system for some years unless work is being done on it. This means the water in the coolant losses the dissolved solids  just once and can then deposit no more. This means you can almost forget about internal scaling.

A direct raw water cooled engine keeps passing new water with dissolved solids in it through the engine so the scale keeps building up until is is so thick it restricts the cooling water flow or insulates the metal so heat can not escape. That is when the head cracks or distorts. This is why its best to use a low temperature thermostat. 72 is better than 82, but 62 is even better.

 

The heat passing through the metal into the cooling system is not evenly distributed throughout the system. Some parts like exhaust valve seats and injector bosses have to get rid of far more heat than other parts so tend to run hotter than what the temperature gauge suggests. When the engine is delivering sufficient power the coolant at these points can boil and scale even more. This is known a localised boiling on the engine hot spots.

A direct raw water cooled boat can not pressurise the cooling system and even if it could you do not need much pressure to push the Jabso impeller wings away from the pump wall and stop/reduce water flow. This means that direct raw water cooled boats have to operate at with the coolant bat atmospheric pressure so the boiling point will be about 100C.

Heat exchanger boats can pressurise the engine part of the cooling system so the boiling point is well above 100C. It is even higher because antifreeze has an influence as well. Thus the running temperature of the engine can be higher than on a direct raw water cooled one without suffering localised boiling. This helps engine efficiency but I doubt an owner would notice.

 

Back to Furness's boat. 

In canal use the engine only produces a few HP so that means less heat to dump into the coolant. You may never get localised boiling with no pressurisation but on a river when you play chicken with the big boys you may well.

If the cylinder head around the heater plug and injector bosses starts to discolour its a sign of localised overheating and it may be too late.

We had such problems with the direct cooled 1.5s on the hire fleet in this respect we did run without a thermostat and changed them to keel cooling with an 82C stat as soon as was practical. That solved the overheating and allowed us to use calorifiers effectively.

  • Greenie 2
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Have been looking closely at my cooling system, and the more I look, the more puzzled I become. A direct raw water cooling system seems very rare and mine doesn't look right somehow. I have been asking several boat owners if they have a direct raw water system to ask if I could have a look,but everyone I asked had either skin tanks or heat exchanger cooling. Happily the boat moored next door but one was direct raw water cooled.[I never thought of asking there]

The owners kindly allowed me to have good nose around their engine room,and I found a few differences to mine. First,their water pump is the standard BMC pump in the front of the engine.Mine has a Jabscoe pump mounted on a bracket on a blanking plate covering the hole where the original pump was.Theirs had two water inlets connected to the water filter,mine has only one.The water bypass on this installation comes out of the cylinder head,on mine,it is in the pipe leading to the engine.

On heat exchanger cooling systems I have looked at,the Jabscoe pump is driven off what looks like a smaller diameter pulley bolted to the engine pulley.On mine it is driven by the engine pulley,and is probably being driven too fast.

I am guessing that my boat has not always been direct raw water cooled and was probably heat exchanger cooled at some time,because with direct water cooling there is no need for an expensive Jabscoe pump, but something went wrong,possibly a corroded heat exchanger,and to save money a previous owner dispensed with the engine driven water pump and simply plugged the raw water pipe from the Jabscoe into the engine,removing the small pulley and using the engine pulley to drive the Jabscoe possibly thinking that the engine would need a greater flow of water than the heat exchanger.Even at tickover there is a steady stream of water from the outlet,squirting about three inches and at cruise about six inches.The more I looked at my system the more "Fred In a Shed" If I may quote Tony Brooks it looked.

 Direct raw water cooling is undesirable for all the reasons given by all the contributors to this thread [localised overheating,scale build up,sediment build up] so I will at some point convert to heat exchanger cooling. Nick at TW Marine Furness Vale showed me some heat exchangers,on the computer,and one I think he said it was a Polar,looks compact enough to fit easily.I will also need a standard water pump,they come in three impeller sizes,60mm 70mm and 74mm,but I don't know yet what size was fitted to mine,untill I remove the Jabscoe  and blanking plate.

Could anyone tell me what the correct gearing is for a Jabscoe pump ?[ What size pulley on the pump to what size pulley on the engine?]

Thank you all for giving me the benefit of your knowledge and experience.

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1.The other boat does not have direct raw water cooling if it really does use the usual engine water pump because they can not prime themselves. I suppose it might be a real bodge because on a narrowboat the water pump MIGHT eb below the water line so with the right pipework the engine may fill itself naturally but if so its a very odd system. You only need one connection from the sea inlet & strainer, no idea what the other one is for so a strange system.

2. Raw water cooling done to a decent standard implies a self priming pump - e.g. a Jabsco.

3. Your blanking plate with a single bypass pipe in it over the water pump hole sounds  like a typical Newage/BMC official marinisation for direct cooling to me. As does the Jabsco on a bracket - A photo would help. Some not so shabby marinisations fitted the Jabsco to them timing cover and drove it from the camshaft

4. An estimate from memory. The pulley ratios by DIAMETER were about 3:1 with the 1 being the engine pulley. The water flow required for heat exchanger cooling was achieved by fitting a larger Jabsco pump. Tell Nick the same size as  DV36 but with the normal higher lift cam fitted.

5. If you are converting to heat exchanger cooling I would suggest that you keep as "standard" as possible and fit a Bowman heat exchanger exhaust manifold assembly. The Polar equivalent now seems to have problems with its rubber end caps.

 

If the engine has been satisfactory so far why change it? It may be a good idea to remove the thermostat again or fit a much cooler one. Remember all this cropped up because you recommended that a member converted his admittedly very dodgy system to a one with known problems. Post a photo and I am sure we can give you more info about your system.

 

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A further thought. Combined sea cock and strainers only have one (outlet) connection on them.

Remote strainers, usually the plastic types, must have two connections. An in from the sea cock and  an out to carry the raw water to the raw water pump. If the other boat has a remote strainer then it will have two pipe/hose connections on it.

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Some pictures of my engine installation.It's direct raw water cooled and I have removed the 82 deg thermostat replacing it with a 74 deg one.

Running the engine today,the temperature barely reached 60 deg after 1 hours running,I was going to take it up the cut to see if it would rise to 74 deg but the weather was 'orrible,rain and sleet.Although the engine had a service last September,as well as changing the thermostat,I gave the mechanics a dose of looking at,syphoned a pint or so out of the tank,[it was clear],drained the gascolator [no water in it] and cleaned the muck from under the filter screen in the fuel pump.With the weather the way it was,and me stinking of diesel,and feeling fed up by this time,I retired hurt and went home.

My boat at the moment is on the Peak Forest Canal,and my home mooring is in Huddersfield.If and when the Marple lock flight opens,it is a four or five day trip,but if I have to go the long way round,[Macc,TandM,Bridgewater] it is likely to be ten  to twelve days.This is why I worry about my engine,I would not be a happy tiger if the donkey handed it's dinner pail in on the way home.

Thanks to everyone for their advice.

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Thanks. OK, its not a official marinistaion (Newage or Tempest).  The exhaust manifold is not water cooled and the bracket for the Jabsco pump is wrong although to my mind it looks better mounted.

The raw water strainer will have two pipe connections because it is remote from the sea inlet.

I can't trace the cooling circuit because the pipes disappear but it does not have the spring loaded bypass that prevents the Jabsco pressure forcing the thermostat open as used on the official version but I can see a T in what should be the supply to the engine but he service valve that looks as if it MIGHT be an adjustable bypass is fully closed. On the other hand it might be a feed/return for a calorifier.

I am mystified by the hose that is T'ed into the pump outlet that runs backwards and then disappears under the starboard deck.

I notice that you have an electric oil pressure gauge. The senders are not the most reliable so if you loose oil pressure just make sure you have oil and there are no leaks. Then the most likely problem will be a faulty sender.

 

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2 hours ago, Tony Brooks said:

I am mystified by the hose that is T'ed into the pump outlet that runs backwards and then disappears under the starboard deck.

Thank you for your views on my cooling system. The hose T'ed into the pump outlet is the bypass.It exits next to the exhaust stbd aft.

I don't really know what you mean by the service valve.If you mean the blanked off pipe on the cylinder head,next to the thermostat housing,it is in what was a blanking plug.I take the blanked off pipe off and flush the engine through with water regularly to help keep sediment down. It is drained out of the valve I fitted in the engine feed pipe [pictures 2 and 4] primarily to quickly and easily drain the engine when I leave the boat for a week or so,if below zero temperatures are forecast. I realise that there is a drain valve on the rear stbd side of the block,but the lever has broken off mine and it is awkward to reach.

When I bought the boat I only had a hull survey done,had I asked for a full survey,no doubt the" Heath Robinson" cooling system would have been noted.Although I have been around engines for many years,a narrowboat installation was new to me.It was only when I bought the boat and looked at other peoples engine rooms and asked "what's that bulbous thing nailed to the side of your engine?"to be told it's a heat exchanger,I wondered why mine doesn't have one.

Anyway,direct raw water cooling is the system my boat has got,and my thanks to you and others for pointing out the shortcomings of this method of cooling.Now that I understand it a little better,I can monitor it for it's known faults.  

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The service valve is the thing I now know you use to open the drain at the front of the engine.

There appears to be nothing to prevent the bypass robbing the  of cooling water when hot apart from hose size and length. I am sure that's fine for canals but when on a river and running hard be ready to clamp the bypass to restrict the bypass flow if the engine overheats. It probably won't but just be prepared in case. The Newage marinisation had a spring loaded bypass valve so it only opened when the thermostat was restricting the main water flow but yours works so don't worry over much..

 

 

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  • 3 years later...
On 04/02/2018 at 11:17, Tony Brooks said:

The service valve is the thing I now know you use to open the drain at the front of the engine.

There appears to be nothing to prevent the bypass robbing the  of cooling water when hot apart from hose size and length. I am sure that's fine for canals but when on a river and running hard be ready to clamp the bypass to restrict the bypass flow if the engine overheats. It probably won't but just be prepared in case. The Newage marinisation had a spring loaded bypass valve so it only opened when the thermostat was restricting the main water flow but yours works so don't worry over much..

 

 

Yes I know I'm guilty of digging up a long dead thread whilst fishing for info on what seems to be the same direct salt or freash water cooled old BMC donkey. I've noted the need to replace the thermostat if one is fitted, with a real cold one, and know my Zinc and Alloy anodes game, (Thinking of fitted one under the pressure cap if the salt water is close enough with the engine running for it to work.

  In the end I'm going down the keel cooling road, but will fit a pair of valves, (1 inch BSP stainless Y valves are kind of expensive), that should allow me to use either raw water, or an internal keel cooling tank.

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1. There is no way I can see of using the ENGINE water pump, as opposed to a self priming Jabsco type, to run raw water cooling.

 

2. Any anode has to be in very good electrical contact with what it is supposed to be protecting. I very much doubt you would get a good, long term, electrical contact by fitting one to the moving part of the pressure cap because it is spring loaded and moves up and down in use.at could be used. There may also be another at the back of the head. They are often blanked with a hexagon screw plug. You do not need an anode in a keel cooler or heat exchanger system because the corrosion inhibitors in the antifreeze will do the job.

 

3. You only need a cool thermostat in direct raw water cooled  engines try to prevent internal furring on the hotspots under high power/speed.. This is because these engines run unpressurised. Keel cooling and heat exchanger engines are fine with a hotter stat.

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26 minutes ago, Tony Brooks said:

1. There is no way I can see of using the ENGINE water pump, as opposed to a self priming Jabsco type, to run raw water cooling.

 

2. Any anode has to be in very good electrical contact with what it is supposed to be protecting. I very much doubt you would get a good, long term, electrical contact by fitting one to the moving part of the pressure cap because it is spring loaded and moves up and down in use.at could be used. There may also be another at the back of the head. They are often blanked with a hexagon screw plug. You do not need an anode in a keel cooler or heat exchanger system because the corrosion inhibitors in the antifreeze will do the job.

 

3. You only need a cool thermostat in direct raw water cooled  engines try to prevent internal furring on the hotspots under high power/speed.. This is because these engines run unpressurised. Keel cooling and heat exchanger engines are fine with a hotter stat.

I was thinking of connecting the cap to a nearby earth point, but you have pointed out there are other places to fit a Zinc. 

 

I've been looking for a low temperature thermostat, but can only find a 72 degree one, when I think your other thread post says 62C. Any ideas, as local boiling is not a good idea, as you previously pointed out.

 

I will probably cost me nearly a grand to fit my old BMC 1500, 500 for parts and another 500 for the RNLI engineer, if I can't find another good marine engineer before the New Year.

 

PS: Do you think the circulating pump has been removed ??

Edited by TNLI
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Thanks to Mad Harold for the pictures posted above, as I now know where to mount the Jabsco pump, also I thought it needed a mounting plate, so will count the bolt holes to figure out which one it is.

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1 minute ago, TNLI said:

I was thinking of connecting the cap to a nearby earth point, but you have pointed out there are other places to fit a Zinc. 

 

I've been looking for a low temperature thermostat, but can only find a 72 degree one, when I think your other thread post says 62C. Any ideas, as local boiling is not a good idea, as you previously pointed out.

 

I will probably cost me nearly a grand to fit my old BMC 1500, 500 for parts and another 500 for the RNLI engineer, if I can't find another good marine engineer before the New Year.

 

You can't fit a bonding strap to the moving part of the pressure cap to which you would have to fit the anode. It is the only part that would allow the anode to poke down through the filler hole. It is possible that this particular engine only has a non-pressurised cap fitted and if so your idea would work because there are no moving parts and typically just a rubber seal. In the late 60s/early 70s 62C stats were available but now direct raw water cooling of marinised industrial/automotive engines is virtually obsolete I expect it will be difficult to find such a low temperature thermostat. You may have r run without a thermostat.

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3 minutes ago, TNLI said:

Thanks to Mad Harold for the pictures posted above, as I now know where to mount the Jabsco pump, also I thought it needed a mounting plate, so will count the bolt holes to figure out which one it is.

 

Oh dear. That is the ONLY 1.5 that I have seen that uses the engine water pump to drive the Jabsco. it is very non-standard and will need a new pulley or drive adaptor machining. I would point out that his front engine mounting is very different to yours and this may make fabricating a bracket for yours more difficult.

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I no longer own the boat illustrated,but I can give a verbal description of it's cooling system from memory.

I fitted a 72 degree thermostat as that was the coolest one I could find for the BMC 1500.

The engine coolant circulation pump was removed and a blanking plate fabricated for the hole.

A foot mountedJabsco pump was mounted on a substantial bracket  and bolted to the engine,can't remember where exactly.

One of the blanking bolts on the cylinder head was replaced with a hose connection for flushing the water jacket.

The pump,and alternator were driven by a single belt.

A restrictor was put in the bypass (a piece of smaller diameter tubing) to slightly increase the pressure in the system.Not by much,as a Jabsco pump with it's rubber vanes will not pressurise the system.It was trial and error to get the right diameter restrictor.Without the restrictor water used to squirt about six inches at tickover and about nine inches when cruising from the hull outlet.After fitting the restrictor it was about three inches and six inches.

It all worked well and never overheated even on the river,however,a pre cruise check was necessary to clear any bits of weed from the inlet strainer and the water filter.

Also when filling the water tank I would put the hose on the connection on the engine and flush the water jacket.

Usually a few seconds of brownish water used to squirt from the hull outlet and then run clear.

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4 hours ago, Tony Brooks said:

 

Oh dear. That is the ONLY 1.5 that I have seen that uses the engine water pump to drive the Jabsco. it is very non-standard and will need a new pulley or drive adaptor machining. I would point out that his front engine mounting is very different to yours and this may make fabricating a bracket for yours more difficult.

I kind of think I need to go down the Keel cooling only road and sell the Jabsco pump! The cost of the new pump and machine shop job, plus 50 quid for the old Jabsco, (They are around 150 quid new), will be the roughly the same as the cost of the internal cooling tank welding and header tank.

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1 minute ago, TNLI said:

I kind of think I need to go down the Keel cooling only road and sell the Jabsco pump! The cost of the new pump and machine shop job, plus 50 quid for the old Jabsco, (They are around 150 quid new), will be the roughly the same as the cost of the internal cooling tank welding and header tank.

Finally, a possibly sensible idea.

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5 minutes ago, TNLI said:

I kind of think I need to go down the Keel cooling only road and sell the Jabsco pump! The cost of the new pump and machine shop job, plus 50 quid for the old Jabsco, (They are around 150 quid new), will be the roughly the same as the cost of the internal cooling tank welding and header tank.

 

Have you seen the Jabsco pump? There is no sign of it in the video. My advice would be to wait until you can post comprehensive photos of the engine so we can see exactly what you have and perhaps offer ideas. If the exhaust manifold cum header tank does not have  a large outlet port then you might need another one suitable for tank/keel cooling.

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3 minutes ago, Tony Brooks said:

 

Have you seen the Jabsco pump? There is no sign of it in the video. My advice would be to wait until you can post comprehensive photos of the engine so we can see exactly what you have and perhaps offer ideas. If the exhaust manifold cum header tank does not have  a large outlet port then you might need another one suitable for tank/keel cooling.

I keep thinking there must be a pump some place, BUT it just occured to me that the chap who restored the engine might have got his comment about it is a raw water cooled version mixed up with a keel cooled version, as there is still a need for a raw water pump for the gearbox oil cooler. 

I'm voting in favour of it being keel cooled, but not sure if I will find out later this afternnon, as the shop chap in charge of the storage area only seems to be there half the time.

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