Electric Water Pump to replace old worn out mechanical, Volvo MD2B

[RogerG]

Hi all,

Been away from this forum for some time due to work pressures but am now semi retired.

My problem is that I have a 1974 Albin 25 Motorsailer with its's original Volvo MD2B engine. The engine was rebuilt a good few years ago with the waterpump being refurbished. I thoroughly checked the engine over before moving the boat from Ely in Cambridgeshire, out to the tidal Ouse leading to Kings Lynn and round through the Wash to a new permanent mooring at Sutton Bridge on the Nene. The total running time was 10 hours, with a quick check at Kings Lynn in the engine sump tray. There was a very small occasional drip from the water pump, but nothing to concern me so I proceeded out into the wash. the engine ran very smoothly all the way, with the last 2 hours showing an increase from 80-90 degrees C on the temperature gauge. On arrival at my new home mooring at Sutton Bridge, I found about 2" of water in the sump tray which amounted to about 2 gallons. I ran the engine again which was instant starting and very smooth, however this time there was a fast trickle of water from the bottom of the pump casing. The impeller was renewed before the journey, so The leak would suggest that the inner shaft seals have gone and probably an ovalling of the shaft contributing.

Bearing in mind that replacement pumps for these old engines are impossible to obtain, do members here think that replacing the pump with an electric, salt and warm water pump would be a practical alternative. The old pump and shaft could easily be removed and a blanking plate put on the block, then the existing piping connected to the electric pump. The pump can be placed below the waterline, so a non self priming pump should be sufficient.

Has anybody else tried this with any success or can offer useful advice or problems I hadn't thought of?

Roger

 

[kashurst]

I would have thought a good marine/machine shop could rebuild it - if necessary modify the seal mount to take a modern equivalent. Or try ASAP supplies to see if there is an upgrade solution with some sort of adapter. I wouldn't go down the electric pump route.

 

[kashurst]

just googled images for your engine. the sea water pump looks very similar to the pump used on farymann single cylinder diesel engines used in all the fischer panda/paguro etc generators. might be worth asking a few questions

 

[RogerG]

Hi Kashurst,

Thanks for the replies and the Farryman similarity is a lateral direction I would never have thought of, I'll see if I can pursue it. As regards a rebuild, I am not sure how practical that would be as it has already been remachined once and probably won't take a second go.

I have found a company that offer a repair kit and they list the MD2B as one of the suitable models. I'll get the old one out and see where the main wear is. It could be something simple like the seals giving out as it hadn't been run for some time, but I am expecting the worst. Any particular reason why you wouldn't recommend the electrical pump route?

Roger

 

[Tranona]

Never heard of an electric pump for circulating water through a seawater cooled engine. The pump runs at engine speed so the higher you rev the more heat you produce the more seawater needed to cool it. Don't see how you can do this with an electric pump.

 

[Jcorstorphine]

Never heard of an electric pump for circulating water through a seawater cooled engine. The pump runs at engine speed so the higher you rev the more heat you produce the more seawater needed to cool it. Don't see how you can do this with an electric pump.

Think it is possible as usual set up for direct seawater cooled engines is that most of the sea water is bypassed into the exhaust with the thermostat opening and closing. Our old BMC Vedette (Morris Minor engine) in my Fathers boat would vary between 70 and 75 and if you felt the exhaust water you could feel the water temp changing from cold to hot every few mins. Going back to OP, he would just need to make sure that the pump was rated to operate against the back pressure from the exhaust and that it had sufficient flow to keep the exhaust cool. The biggest problem is interlocking the pump so that it does not flood the engine in the case of a prolonged starting issue. The danger being the exhaust pipes gets filled with water and falls back into the engine. He also needs to ensure the pump stops as soon as the engine.
There are various ways of doing this from either the alternator or a pulse counter off flywheel teeth however engine may not have teeth on flywheel as could be dynostart.
I would have thought best option would be to go for a belt driven Jabsco and fit an extra pulley on the flywheel. One slight snag being the flywheel bolt on MD2B requires a torque of 500 No and that is a metre long torque wrench.

 

[Jcorstorphine]

Bl00dy iPad, changed Nm to No cos it think I don't know what I am doing.
Yes it is 500 Newton Metres and that need two of the biggest fitters in our workshop to help me when I was rebuilding my MD2B

 

[RogerG]

Never heard of an electric pump for circulating water through a seawater cooled engine. The pump runs at engine speed so the higher you rev the more heat you produce the more seawater needed to cool it. Don't see how you can do this with an electric pump.

Hi Tramona and Jcorstophine, thanks for your input.

I haven't heard of an electric pump for circulating raw water through a marine engine either, however I don't really see why it shouldn't be perfectly feasible. As was mentioned, the raw rather is passed continuously through the engine and then while the thermostat is closed it passes directly to the exhaust outlet. It only circulates through the engine once the thermostat opens. I am unsure as to why this could lead to engine flooding as any surplus water should bypass straight through. The MD2B worship manual mentions this constant through flow, with the opening and closing thermostat regulating the flow through the block.

Roger

 

[Jcorstorphine]

Hi Roger. The danger I am referring to is based on the following non interlocked electrical pump.
1. You swich on engine power and you turn the key to start the engine.
2. This action brings on the elect water pump.
3 You continue cranking but engine has an air lock in the fuel line and does not start.
4 During this period the elect pump has been pumping water through the bypass into the exhaust but due to only moderate pressure from the engine, not all of the water is expelled as it would be when the engine is running and assuming you have some form of U bend in the exhaust pipe, when you stop cranking, water may find its way back into one of the cylinders through an exhaust valve.

This has been reported a number of times on these forums even with convention setup pumps and ends up with major stripdown due to seized pistons.

 

[RogerG]

Hi Roger. The danger I am referring to is based on the following non interlocked electrical pump.
1. You swich on engine power and you turn the key to start the engine.
2. This action brings on the elect water pump.
3 You continue cranking but engine has an air lock in the fuel line and does not start.
4 During this period the elect pump has been pumping water through the bypass into the exhaust but due to only moderate pressure from the engine, not all of the water is expelled as it would be when the engine is running and assuming you have some form of U bend in the exhaust pipe, when you stop cranking, water may find its way back into one of the cylinders through an exhaust valve.

This has been reported a number of times on these forums even with convention setup pumps and ends up with major stripdown due to seized pistons.

Now I get your point basically the same as stalling your car while driving through a ford! So the answer would be to find a way of limiting the flow until the engine fires up, perhaps a solenoid switched by the alternator output. I should add that it is all hypothetical until I have fully checked the existing pump, but interesting nevertheless and potentially very useful.

Roger

 

[vas]

I had to rebuilt my generators sea water pump twice until it worked fine and that included new shaft, seals, machining the body to get bigger seals in, new key, etc. Still, it's a device that I can get in my hands in ten min, no sensors, El. Cables and complex methods to keep seawater out of my yanmar 20 cylinders.
I'd recommend fixing or a new pulley and a 200 jabs of or other pump!


Cheers

 

[RogerG]

I had to rebuilt my generators sea water pump twice until it worked fine and that included new shaft, seals, machining the body to get bigger seals in, new key, etc. Still, it's a device that I can get in my hands in ten min, no sensors, El. Cables and complex methods to keep seawater out of my yanmar 20 cylinders.
I'd recommend fixing or a new pulley and a 200 jabs of or other pump!

Hi Vas, thanks for the input.

I suppose I was hoping lots of replies would support my electric pump idea, but sadly not to be. The Jabsco replacement is an idea that I might have considered if I had the engineering skills to do the work myself,. I haven't, so on top of the £400 plus for the pump and fittings, a new crankshaft pulley belts and bits and the considerable labour charges it is likely to be an up to £1500 job. Much as I love the boat and engine I really wouldn't want to contemplate that sort of outlay to repair a leaky pump on a 43 year old engine. The other option of a further rebuild is probably the better one, so I'll see what I find when the old one comes out.

Roger


Cheers

 

[RogerG]

I thought I would post an update. A couple of days ago, despite living in a small village, I found a precision engineering company in an old scout hut in the owners back garden. Although I have lived here over 3 years I had never seen it before and spotted a small sign by chance while walking the dog. It's only 3 mins walk from my house, so I paid them a visit and spoke to the owner and his two engineers, both old school very friendly and who were delighted to look at the pump.

I took the pump off the engine block and could see a slight gap around the rear seal and some lateral movement in the shaft. I decided to leave it assembled and took it to the workshop yesterday. I had a phone call this morning asking if I could come by and look at what they had found. The pump was completely disassembled and clearly needed new seals, the main shaft had a very noticeable groove around it caused by oscillating around the middle seal. The main casing was completely undamaged which the engineers were surprised about and they had already sourced new seals, which they were happy to put on the old shaft if I didn't want to go for a shaft replacement. Their advice though was to replace it as the new seals would quickly be damaged by the movement. I completely agreed with that, so the repair will consist of a new shaft which they will fabricate from scratch, new seals, reworking the impeller housing end plate which was bowed and had been reversed by a boatyard mechanic recently. The engineers felt that the now inward bowing would but pressure against the shaft and seal, so are going to completely flatten the plate in their press, repolish it and refit with a new gasket. Finally they will clean and polish the whole pump casing.

Total cost for all this work? £90-100 depending on the cost of the seals. I am amazed to find that such friendly, honest and down to earth businesses still exist and would happily recommend to anyone in the east of England area who needs an estimate for this type of precision engineering work. Not sure if I am allowed to post details but message me if anyone wants contact details.

Roger

 

[Jcorstorphine]

Hi Roger, good result. Best way forward is by far to get your pump rebuilt. They sound a good bunch of guys. If you have a min, can you PM me their details.

 

[vas]

Total cost for all this work? £90-100 depending on the cost of the seals. I am amazed to find that such friendly, honest and down to earth businesses still exist and would happily recommend to anyone in the east of England area who needs an estimate for this type of precision engineering work. Not sure if I am allowed to post details but message me if anyone wants contact details.

Roger

Brilliant outcome!
that's what my machinist did to my yanmar pump, fabricating a shaft is no such a big deal after all.. Having some old school REAL mechanics is invaluable if you own an old boat/engine.
very well done!

cheers

V.

 

[Sailerbailer]

I would be interested in details of the engineers who machined a new shaft. My water pump shaft is also worn, so the pump leaks. Its a yanmar ysb12, so it may be easier to have one made if i can't find a replacement.

Many thanks