Engine driven bilge pump...

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Swenns Dad

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Hi all.

Just in process of replacing the thru hull hoses. I’m also changing bilge pumps and, in the process of doing so wondered if I could effectively divert the raw water inlet pipe to another hose, for the purposes of using the engine driven raw water pump as an emergency bilge pump?

Anyone ever seen this? Obviously, the hose would need a coarse strainer on it.
 
Yes.

If you’re prepared to set up a manifold system. I ve seen them for bilge/fire systems, but usually a separate pump.

The problem with using the cooling pump is if it runs dry you’re now without an engine.

W.
 
When you look at the flow rate through the raw water pump, it won’t add a vast capacity. If you’re seriously looking at increasing the bilge pump capacity then a bigger electric pump will deliver greater capacity. However, nothing whatsoever to stop you doing as you suggest, using a T valve to switch between the normal inlet and a hose routed into the bilge. Worth doing if it’s a relatively easy fix.
 
This suggestion pops up from time to time. An engine raw-water cooling pump has nowhere near adequate flow capacity to act as an emergency bilge pump. Sorry.
 
I have seen one, where you clamped an impeller and housing, around the prop shaft, and rportedly, that worked well, as long as you have a long enough run of shaft, to be able to mount the system.
Going through a rubber impeller, with probably an aluminium housing, would probably need a very fine filter, since just fine particles of sand, in the housing, would act like grinding paste, which would work, if you were not far from home.
How long it would remain effective, on a long trip, is anyones guess.
Running outboards, in silty water, or shallows, destroys the pump housing, in short order.
 
duncan99210 said:
When you look at the flow rate through the raw water pump, it won’t add a vast capacity. If you’re seriously looking at increasing the bilge pump capacity then a bigger electric pump will deliver greater capacity. However, nothing whatsoever to stop you doing as you suggest, using a T valve to switch between the normal inlet and a hose routed into the bilge. Worth doing if it’s a relatively easy fix.
Click to expand...

I had thought that, not a huge flow through the cooling pump, but I suppose it could be the difference between surviving long enough to be rescued, or not. Noting a couple of high flow electric pumps and a couple of manual whale pumps are also going in...

Whale do a y valve which would do the job nicely, by the look of it.

Maybe I’m going bilge pump crazy!
 
earlybird said:
This suggestion pops up from time to time. An engine raw-water cooling pump has nowhere near adequate flow capacity to act as an emergency bilge pump. Sorry.
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Don’t disagree, wrt the flow. Not considering it as a pump to use in any situation other than, float or sink situations.... as I suppose any additional bailing of water must be a good thing, if you’re in the unfortunate scenario to need it ?
 
Swenns Dad said:
Hi all.

Just in process of replacing the thru hull hoses. I’m also changing bilge pumps and, in the process of doing so wondered if I could effectively divert the raw water inlet pipe to another hose, for the purposes of using the engine driven raw water pump as an emergency bilge pump?

Anyone ever seen this? Obviously, the hose would need a coarse strainer on it.
Click to expand...
I would certainly not do that for a bilge pump that may be required in an emergency. Even with a filter, if the system blocks and/or runs dry you will then have an overheating engine and therefore a second emergency to sort out. Too risky. I would ensure all bildge pumps systems are independent.

Www.solocoastalsailing.co.uk
 
Plum said:
I would certainly not do that for a bilge pump that may be required in an emergency. Even with a filter, if the system blocks and/or runs dry you will then have an overheating engine and therefore a second emergency to sort out. Too risky. I would ensure all bildge pumps systems are independent.

Www.solocoastalsailing.co.uk
Click to expand...
Yeh, sound points made. Maybe an independent engine driven pump is the way ahead.
 
Plum.
Swenns Dad, is talking about using one of those Y valves, with a lever.
If the bilge got dry, or the hose blocked, he could just flick the lever, and be back to raw water cooling.
 
STILL AFLOAT said:
Plum.
Swenns Dad, is talking about using one of those Y valves, with a lever.
If the bilge got dry, or the hose blocked, he could just flick the lever, and be back to raw water cooling.
Click to expand...

The problem is you have to be watching it and in the situation you’re using it distraction is likely.

The only issue with a separate pump is you need to be circulating water through it all the time the engine is running to avoid destruction of the impeller. Or fit some form of clutch.

W
 
PilotWolf said:
The problem is you have to be watching it and in the situation you’re using it distraction is likely.

The only issue with a separate pump is you need to be circulating water through it all the time the engine is running to avoid destruction of the impeller. Or fit some form of clutch.

W
Click to expand...
Yeh, agree.

Suppose I could also fit a flow switch between the engine pump and the strainer, linked to an alarm.

That will also warn me if the raw water inlet ever blocks up too.

?
 
Swenns Dad said:
Yeh, agree.

Suppose I could also fit a flow switch between the engine pump and the strainer, linked to an alarm.

That will also warn me if the raw water inlet ever blocks up too.

?
Click to expand...

if your in a position to do so I would fit one anyway.

I had IIRC a Perkins impeller fail, in the maybe 15 seconds it took my engineer to fall out of his seat and get to the engine room we had melted a fair amount of the water cooled exhaust system.

This was despite shutting it down as soon as the alarm went off and it was at relatively low RPM.

W.
 
PilotWolf said:
if your in a position to do so I would fit one anyway.

I had IIRC a Perkins impeller fail, in the maybe 15 seconds it took my engineer to fall out of his seat and get to the engine room we had melted a fair amount of the water cooled exhaust system.

This was despite shutting it down as soon as the alarm went off and it was at relatively low RPM.

W.
Click to expand...

Any recommend on a make/model of flow switch?
 
If you really want a serious capacity increase perhaps add an extra engine-driven pump which can readily be connected/disconnected from the engine. A friend had such a pump when he kitted out his boat for 'round the world'.

As for the drive connection, you could perhaps set a belt-driven pump with a pivoting, over-centre latching idler wheel to tension the belt, thus being able to quickly put on the loose belt and instantly tension it up with a lever on the idler wheel pivot.
 
Re inventing the wheel ?
stuart seacock s had a tapping especially designed as a bilge pump connection but that was before GRP so most wooden boats required regular bilge pumping circa 1950s you used the off on lever to select water source
it worked reasonably well but was only 3/8 BSP as I recall so not exactly fast but for non emergency use it was ideal
 
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