Replace raw water pump with electric?

[Rivers & creeks]

We had some issues with our Jabsco engine raw water pump this summer with it overheating, possibly due to bearings. One possibility is to have it reconditioned - any suggestions for that by the way? The other idea I had was why don't engines have electric ones? A new replacement Jabsco is about £500 but an electric one would be about £150 - do any engines use them?

 

[Tony Cross]

Would an electric one not need to vary the volume pumped with engine revs as the mechanical ones do? Otherwise at low engine revs you'd fill the exhaust box with seawater which the low revs exhaust gasses couldn't flush out, perhaps risking water getting back to the engine?

 

[Anchorite]

Yes I have fitted an electric pump: my worry was that it would not provide enough cooling water but there have been no problems since fitting it. I don't think the variable speed/flow complication mentioned above holds water! I also fitted a flow indicator connected to a (loud) alarm.

 

[PCUK]

It's more likely it overheated due to lack of water. Get a service kit and do it yourself. The electric pump idea is just silly.

 

[lynall]

Looking at it from a practical point of view, its obviously cheaper for the engine manufacturer to fit an electric raw water pump, the question you should be asking is why didnt they?

 

[parbuckle]

I would imagine engine manufacturers pay only a fraction of the spares cost you can buy a small outboard for £500.

 

[pvb]

We had some issues with our Jabsco engine raw water pump this summer with it overheating, possibly due to bearings. One possibility is to have it reconditioned - any suggestions for that by the way? The other idea I had was why don't engines have electric ones? A new replacement Jabsco is about £500 but an electric one would be about £150 - do any engines use them?

I wouldn't risk an electric pump, raw water output should vaguely be in sync with engine revs ideally. The typical Jabsco pump is so incredibly simple that there surely can't be a problem fitting new bearings in it - even if you pay someone to do it?

 

[concentrik]

I'm making an assumption here (risky I know) that it's the engine overheating not the pump itself.

When we had baffling engine overheat probs I fitted a 'water puppy' electric impeller pump in series with the mechanical pump. I figured that the mech pump would have some effect in regulating the water flow and it probably did. There was never any problem with 'flooding'. The exhaust pressure is so great that you can't fill the exhaust box when the engine is running. Not so when the engine is starting or stopped though... turn the electric pump off first!

Although it worked (and is still in parallel now just in case) you might want to try to find the underlying problem. I disconnected the output from the raw water mech pump and started the engine briefly to see the flow... gushes! Then did the same at various points in the circulation, finding that the flow was down to a dribble at the output from the oil cooler. After cleaning the cooler by pressure back-flowing it, good flow was restored. Engine now always at correct temp.

Our prob was caused by the debris from numerous impeller shreds building up in the cooler tubes... a small coarse pre-filter was fitted to collect any material before it gets to the constricted cooler tubes.

 

[NormanS]

I agree with those who say to check the whole system, and not just the pump. When I took the exhaust elbow off mine a few weeks ago to check it, I found that the bore of the water connector, (which fell apart in my hand, but that's another story), was reduced to a tiny hole. Strangely, it hadn't yet had any effect on cooling, but it must have been close.

 

[silver-fox]

It's more likely it overheated due to lack of water. Get a service kit and do it yourself. The electric pump idea is just silly.

The idea of an electric water pump is not "just silly" as evidenced by the experience of other contributors to this thread.

Of course you are entitled to express your opinion but its not very enlightening unless you explain why you hold it.

So, if the idea is a silly one, tell us why please and we can avoid making a silly mistake.

 

[pete]

A mechanical pump will be probably be much more reliable overall but I do see your point about the price difference after just replacing the mechanical pump on my Yanmar that had a badly worn body with a direct replacement. If you do go for an electric pump be sure to wire in something to prevent the pump pumping should the engine stop unexpectedly with a rope around the prop etc.

Pete

 

[Leighb]

Just a thought, once a diesel engine has started it normally needs no electrical power to keep running. If for some reason there is a total power loss the engine will keep going until you shut it down. If you replace a mechanical pump with an electric one this is no longer true. It may of course not matter as the risk is minute?

 

[rob2]

Some people converted their direct cooled engines to indirect using a proprietary kit (can't remember the trade name...) which used an electric pump. I believe some also fitted warning devices in case of failure. I'd certainly advocate a piddling anti-siphon device so you have a tell-tale to confirm it's working.

Rob.

 

[pvb]

Some people converted their direct cooled engines to indirect using a proprietary kit (can't remember the trade name...) which used an electric pump.

But that electric pump would only be to circulate the coolant. The problem with using an electric pump for the raw water is that it must only operate when the engine's actually running, otherwise it'll fill the exhaust with water and wreck the engine. That means further complication, probably with a relay controlled by an oil pressure switch. And if the pump can supply enough water to cool the engine at high revs, it may supply more water than the exhaust can easily blow out at idle speed.

 

[David2452]

Some people converted their direct cooled engines to indirect using a proprietary kit (can't remember the trade name...) which used an electric pump. I believe some also fitted warning devices in case of failure. I'd certainly advocate a piddling anti-siphon device so you have a tell-tale to confirm it's working.

Rob.

I remember those, a lot of them were done to convert V8s in the states (where they were made) the coolant pump was retained and the electric pump was used for the raw water, very popular at one time.

 

[ghostlymoron]

I agree with pcuk stick with original equipment. Simple, reliable, easy to service, flow matches revs, no rewiring or dodgy connections - do I need to say more?

 

[charles_reed]

For my last two engines I've always carried a spare raw water pump.
Mainly because on the 2GM Yanmar it was easier to change the pump than the impeller.
My experience has been that for every 3 impellers you have to replace water-seals and bearings.
In Crete I managed to get seals and bearings for the Johnson pump for about €6, the actual Johnson parts cost about £15, but their waterseal has a ss spring.
I had the Jabsco on the 2GM re-machined (you get internal scoring on front and rear faces which cripples the pump performance) for £8.
New pumps are between £240 and £290. 2nd hand they cost about £150.
I now only replace impellers once, before stripping and rebuilding with all new parts, my raw-water pumps. With a decent pre-filter impellers do <600hours.
Don't actually see the purpose of replacing the designed pump with a makeshift device such as an electric pump, no cost benefit and major reliability handicaps.

 

[makingplansfor]

We had some issues with our Jabsco engine raw water pump this summer with it overheating, possibly due to bearings. One possibility is to have it reconditioned - any suggestions for that by the way? The other idea I had was why don't engines have electric ones? A new replacement Jabsco is about £500 but an electric one would be about £150 - do any engines use them?

What Jabsco pump do you need - I had some drama early this season which led to me now having 2 spare pumps (one with only 10 hours run but a cracked shaft collar) and bits - said pump is a Jabsco 3270. Let me know if any of these parts are of interest??

 

[Rivers & creeks]

Thanks - I'll try and identify the model - I discovered in the summer that there are hundreds. It's definitely the pump not the engine overheating. We've cleared out all the water pathways and replaced the oil cooler. The pump overheated in the summer, the disc inside the housing that's visible was glowing red hot. Consensus is it needs new bearings but I don't know who to approach to do that. The new price was ridiculous - £500ish.