Using a bilge pump as a temporary (emergency) raw water pump

[NickWilson1972]

I was going to launch my yacht on Friday but predictably the raw water pump failed. It isn't the impeller and looks like a pump wear issue. Replacing DIY is beyond my skills set (probably) and certainly not in my time availability.

I am at a club and nearest marine engineer is 5 miles away and won't travel. I have several other jobs I had put aside for end of season but thought why don't I just drop the yacht into the marina for a week and get them all done.

Yacht is a Hunter Channel 323 (4500Kg) so I need engine power to launch and get up the channel to the marina. When I had a similar problem with a Hunter Horizon 272 I did it with a Haswing 24v 2.0 on a hang off the stern mount which worked. I don't think that is an option with a 32 footer.

How about rigging up a 500-750gph bilge pump on a pole with a pipe going to the inlet port on the impeller housing. Id take the impeller out and just flush raw water through the engine raw water cooling system . I would put fine mesh around the BP intake to minimise weed etc. Even at 30% of rated flow the BP will be delivering 16 litres of water per minute. The engine is a Nanni 21.

I know there are limitations but do people reckon this is feasible for a launch and 5 mile journey?

 

[Channel Sailor]

I suggest get it towed up the channel.

Why, well a number of reasons, but one would be what happens if the temporary measure fails halfway along the channel. You would need a tow then anyway (after it has been pulled out of a mud bank).

Other reasons would be: proving to yourself you will not cause a hydraulic lock in the engine. You don’t know for sure the pump body has failed, it could be something else that complicates your plan.

Maybe delay your plan so you can acquire the necessary DIY skills to fix it yourself.

 

[NickWilson1972]

I suggest get it towed up the channel.

Why, well a number of reasons, but one would be what happens if the temporary measure fails halfway along the channel. You would need a tow then anyway (after it has been pulled out of a mud bank).

Other reasonsroving to yourself you will not cause a hydraulic lock in the engine. You don’t know for sure the pump body has failed, it could be something else that complicates your plan.

Maybe delay your plan so you can acquire the necessary DIY skills to fix it yourself.

Cheers

If I pack out the impeller housing with grease / glycerin it works for a minute or two which indicates its a wear issue and as the grease clears the lack of flow resumes. Its a speed seal mount (original without the bearing) and I have saned it down as well as the opposing face which hasn't worked.

Contingencies against the problems you raise.

• Test on land first
• install back of stern mount which I can mount a 3.5HP mariner on and the electric. Certainly enough to give steerage.
• Ensure sails can be used - its only actually the launch and marina where I need the engine
• Ensure hook is ready to drop
• Have a spare BP ready and wired just incase. The cheapo seaflo's cost nothing

Problem with delaying plan is the yacht then becomes another sailing club caravan. I want to sail. I have learnt from experience that the 1.5 hour round trips to learn simply isn't worth the time when that resource is limited.

 

[mogmog2]

Replacing the water pump on a Kubota D722 (Our Beta 20, your Nanni N3.21) is absolutely not difficult: The sensible option would be to get one delivered pronto and swap it over - no precarious alternatives or whatever.

The University of Youtube will show you how to do it - most engines are pretty much the same ( loosen alternator, remove belt, undo probably two bolts that hold the pump on with little clampy things, see pic (probably one of them is a bit awkward to get to), put new pump in. redo clampy things, put belt back on (maybe replace as well for good measure) and tension. Job done. Cup of tea time

Othere info that may be of interest:
IIRC pumps like the Johnson F4B & Jabsco equivalents run at around 40 lpm
FWIW in our Centaur (ca 3.5t) we got towed across a (millpond) Solent by a mini tonner with a 2.2 Merc!

 

[NickWilson1972]

Replacing the water pump on a Kubota D722 (Our Beta 20, your Nanni N3.21) is absolutely not difficult: The sensible option would be to get one delivered pronto and swap it over - no precarious alternatives or whatever.

The University of Youtube will show you how to do it - most engines are pretty much the same ( loosen alternator, remove belt, undo probably two bolts that hold the pump on with little clampy things, see pic (probably one of them is a bit awkward to get to), put new pump in. redo clampy things, put belt back on (maybe replace as well for good measure) and tension. Job done. Cup of tea time

Othere info that may be of interest:
IIRC pumps like the Johnson F4B & Jabsco equivalents run at around 40 lpm
FWIW in our Centaur (ca 3.5t) we got towed across a (millpond) Solent by a mini tonner with a 2.2 Merc!

cheers


It looks like the d1 MD 120S MS series Volvo 3593654 / Johnson 10-24751-01.

I know what ever I buy, irrespective of the amount of research won't fit.....

 

[Iliade]

Where is the boat? Someone here may be able to offer a tow.

 

[Channel Sailor]

“I know what ever I buy, irrespective of the amount of research won't fit.....”

Suggest take the old one off first, take it to the spares dealer to make sure you get the right one. Or take lots of photo’s of it for them. Or try to buy it on a sale or return basis.

 

[NickWilson1972]

Blackwater - Marconi

Would be a nice offer (and I would cover diesel costs and a generous bar allowance) but requires a fair degree of coordination.

Also have to launch first which requires engine power unless a rib used to tow you off

 

[NickWilson1972]

Where is the boat? Someone here may be able to offer a tow.

Blackwater - Marconi



Would be a nice offer (and I would cover diesel costs and a generous bar allowance) but requires a fair degree of coordination.



Also have to launch first which requires engine power unless a rib used to tow you off

 

[iamtjc]

I know what ever I buy, irrespective of the amount of research won't fit.....

I spent weeks on my water pump on a Nanni 2.14
New seals, impeller, flattening the faces etc.

In the end bought a new pump from A R Peachment (the Nanni distributor).
They know their stuff and will send the right part.
Half an hour later all my water pump woes were a thing of the past. Probably one of the best bang for the buck purchases I have made.

 

[NickWilson1972]

I spent weeks on my water pump on a Nanni 2.14
New seals, impeller, flattening the faces etc.

In the end bought a new pump from A R Peachment (the Nanni distributor).
They know their stuff and will send the right part.
Half an hour later all my water pump woes were a thing of the past. Probably one of the best bang for the buck purchases I have made.

Cheers. Thanks for the tip

The point 'spent weeks' is the whole crux of this

 

[mogmog2]

cheers


It looks like the d1 MD 120S MS series Volvo 3593654 / Johnson 10-24751-01.

I know what ever I buy, irrespective of the amount of research won't fit.....

ASAP do a parts ID service - free. And Marine Service Kits are pretty clued up IME. On our old MD2B, the pump seals didn't match the normal ones, but they got there after I sent photos. The whole pump should be easier as there are only two critical buts: the flange mount type/size and the shaft drive style (some shafts have a tab that goes into a fork in the engine side and others it's vice versa - easy to see the difference).
I'm not sure if the clamp on flanges are engine specific, but again should be easy enough.

 

[NickWilson1972]

Update.

I managed to repair. I sanded the back of the speedseal plate until all the ribbing had gone with an orbital sander using progressively finer grades of paper. I went up to the yacht and did the same on the pump plate. greased down the impeller with glycerin and the back of the speed seal plate and O ring. Installed and raw water being drawn through adequately for 15 mins with no sign of diminishment. Certainly good enough to launch next Saturday.

Thanks all for advice and opinions. I am still interested in the concept of using a bilge pump as an emergency form of engine cooling in the event of a failure at sea which can't otherwise be resolved. I shall discuss with my marine engineer end of season for his views.

 

[ridgy]

I just rebuilt my 2GM pump with a kit from Marine Service Kits. It had suddenly started leaking quite badly but when I stripped it down I also found that the bearings were seized and it was hard to turn by hand so I'm surprised the belt had not been worn out. They are actually very simple things and easy to rebuild. It required a bit of youtubing for the first time but now I could do it again in 10 minutes.

Once you understand how they work you will also understand how fundamentally reliable they are and this would be a more worthwhile exercise than trying to imagine some lashup with a bilge pump. I suggest that you google "bilge pump duty cycle" before you spend any more time on the idea.

 

[mogmog2]

I just rebuilt my 2GM pump with a kit from Marine Service Kits. It had suddenly started leaking quite badly but when I stripped it down I also found that the bearings were seized and it was hard to turn by hand so I'm surprised the belt had not been worn out. They are actually very simple things and easy to rebuild. It required a bit of youtubing for the first time but now I could do it again in 10 minutes.

Once you understand how they work you will also understand how fundamentally reliable they are and this would be a more worthwhile exercise than trying to imagine some lashup with a bilge pump. I suggest that you google "bilge pump duty cycle" before you spend any more time on the idea.

I was just thinking that, if I was that worried about water pump failure, I'd buy a spare - either an aftermarket one, or get one off eBay and refurbish it with bits from MSK.
Possibly no harder to swap over, than to rig a reliable bilge pump alternative.

 

[ridgy]

I was just thinking that, if I was that worried about water pump failure, I'd buy a spare - either an aftermarket one, or get one off eBay and refurbish it with bits from MSK.
Possibly no harder to swap over, than to rig a reliable bilge pump alternative.

Absolutely, changing the pump is a 5 minute job on a 2GM, just undo 2 bolts and 2 hose clips, and I can't imagine it being much more difficult on any other engine. Given that a kit with all new internals including the cover plate and the shaft was about £120, a new pump is absurdly expensive at about £360 but other than a drip through the water seal there is nothing to break on a rebuilt pump. I bought a spare water seal at the same time but I don't imagine using it for years and there is really nothing else to fail apart from the belt which is a consumable item anyway.

 

[PabloPicasso]

Okay here we go.

1. Will an electric bulge pump give too little water

2 . If it gives too much you risk hydrolocking the engine with associated damage (i.e., it may fill the exhaust up and pour back in through the exhaust port as it opens potentially causing catastrophic damage. How would you know until it was too late?

3. With careful supervision it perhaps could be made to work. Ideally a speed variable pump matched to engine rpm. requirements.

4. I suppose a manual bilge pump might work for a short time, such as entering a harbour or marina. It will need careful monitoring and coordination, and a fit willing crew, oh Yes, and a mechanically strong reliable bilge pump

It.might be easier to call for a tow. Paying for a tow may workout less than a blown engine