Bilge influx and pump issues

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webcraft

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Those following our saga with Avy-J, our 'rescue yacht' Morgan Giles 30, will know some of the history. A new engine should have sorted all major trauma, but...

The boat is still leaking...

(For history, it always has, a bit, but there were too many other things to worry about and a 500gph Orca pump with field sensor switch took care of it until the pump and switch failed, probably due to oil contamination from the leaky old engine, now gone)

Stern gland is tight for now and not dripping (we are at anchor). There is a slight weep (a tablespoon or less in 12 hours) from the log transducer, butIMG_20211019_094623_1.jpgut otherwise the bilge forward of the main sump is dry.

The sump is a sort of round basin which is presumably sitting inside the long keel. I currently have a 500gph Tsunami pump in this sump, with a Whale field sensor switch. See the image above.

There is maybe a litre accumulating over 12 hours. The water has a slight brown (rusty?) tinge, and I think it may be coming out under the lip of the sump pan.

Could this be water that is somehow getting into the encapsulated (cast iron) keel then finding it's way round the incompletely bonded sump pan? If so, might another tube of water weld epoxy be a good investment as a temporary solution prior to a major investigation the next time the boat is out of the water?

(For info, when the boat was lifted there was no evidence of any water draining out from the keel anywhere, though there was a little from the rudder)

Re. the current bilge pump - it is a cheap 500gph (nominal) Tsunami, and it seems to be struggling with a 4ft head and about 3m of 3/4“ pipe with a couple of sharpish bends in it. The field sensor switch is dead, new water witch on order, but I think I need a bigger pump, maybe 1100gph. That is as big as I can go with the existing outlet.

(Please remember when responding that this is a MAB we rescued from the scrapheap, it is not as far as I can tell in imminent danger of sinking so please no tales of horror and we have just relaunched so cannot afford to haul and start major work right now)

- W
 
I notice that the sump well is a 'pot' only secured with some rusty screws, so water could be leaking up from below as you suggest. Maybe leaking in around the rudder pintle fastenings? I always wanted a MG30!
 
Did you undo those three screws and try removing the sump pan while the boat was out?

What is the encapsulated keel made of?
If it's scrap steel punchings with resin poured over, and now it's rusting, the growth of the rust can put a lot of stress on the hull.
Water leaking up through an encapsulated keel doesn't sound good.

More likely, the water is getting in elsewhere and just getting under the rim of the sump and mingling with the crud that's under the sump.

Those centrifugal pumps are not right for this application.
You need to chase the moths out of your wallet and buy a proper diaphragm pump.
When your toy pump stops, all the water in the pipe will run back, nearly enough to re-fill the sump?
Get something proper that pumps air and blows the water out of the plumbing.
Then use a sponge to empty the sum and see what's going on.

The sump looks like it was made to be removed. It would have been trivial to glass it in, somebody made a definite decision not to do that.
How about drilling a small hole in the bottom of it, which can then be sealed with a self tapper and a rubber washer?
Find out if there is a finite amount of water in play or whether the ocean is passing through your keel?
I put this on here as an idea, might provoke some thoughts from people familiar with exactly how the boat was built.

I think I'd want to remove the sump, get the void under it dry, then seal the sump properly.
If there is a void under the sump, and if it can be got dry.

But then I'm not a boatbuilder, designer or naval architect, I do other sorts of engineering.
 
neil_s said:
I notice that the sump well is a 'pot' only secured with some rusty screws, so water could be leaking up from below as you suggest. Maybe leaking in around the rudder pintle fastenings? I always wanted a MG30!
Click to expand...

Aha! Upper rudder pintle fastening sounds a likely candidate.

I presume fixing that would involve rudder removal and precision engineering...


- W
 
Last edited:
Wing Mark said:
Those centrifugal pumps are not right for this application.
You need to chase the moths out of your wallet and buy a proper diaphragm pump.
When your toy pump stops, all the water in the pipe will run back, nearly enough to re-fill the sump?
Get something proper that pumps air and blows the water out of the plumbing.
Then use a sponge to empty the sum and see what's going on.
Click to expand...

Something like this?
Jabsco Electric Diaphragm Bilge Pump 31705-0092

Is that designed to sit above the sump with an inlet pipe going into the sump?


The sump looks like it was made to be removed. It would have been trivial to glass it in, somebody made a definite decision not to do that.

I think I'd want to remove the sump, get the void under it dry, then seal the sump properly.
Click to expand...

Yeah, think I will remove the screws and see if the sump lifts out and what lies underneath. I will wait until we are in a marina near a hoist rather than at anchor though. Wish I had done this when the boat was on the hard recently, but of course the issue only raised itself when we launched.

- W
 
Sprinkle a load of talcum powder all over the place & when you return to the boat the path of the water will be obvious. So some round the pintals will show straight away if they are leaking. Same for other penetrations through the hull.
Do not discount windows, plus shroud & deck fittings leaking when it rains. Water could be ponding somewhere else ie in stringers & leaking through slowly
 
Daydream believer said:
Sprinkle a load of talcum powder all over the place & when you return to the boat the path of the water will be obvious. So some round the pintals will show straight away if they are leaking. Same for other penetrations through the hull.
Do not discount windows, plus shroud & deck fittings leaking when it rains. Water could be ponding somewhere else ie in stringers & leaking through slowly
Click to expand...

It's not rained significantly in the Algarve for months, and the sump was bone dry before we launched 4 days ago, so it's def. a current leak.

Talcum powder is a good idea!

- W
 
webcraft said:
Something like this?
Jabsco Electric Diaphragm Bilge Pump 31705-0092

Is that designed to sit above the sump with an inlet pipe going into the sump?




Yeah, think I will remove the screws and see if the sump lifts out and what lies underneath. I will wait until we are in a marina near a hoist rather than at anchor though. Wish I had done this when the boat was on the hard recently, but of course the issue only raised itself when we launched.

- W
Click to expand...
Yes, that's the type of pump I had in mind.
If the underside of that sump is open to the sea, and the bottom of it is 18inches below the waterline, it's an exercise for the reader to work out the pressure and force on it.
Once you break the seal, those little screws are unlikely to hold it ever again.
I would not disturb those screws while afloat, at least not without drilling a small hole in the bottom of the sump to check there's no significant water pressure behind it.
 
Wing Mark said:
Yes, that's the type of pump I had in mind.
If the underside of that sump is open to the sea, and the bottom of it is 18inches below the waterline, it's an exercise for the reader to work out the pressure and force on it.
Once you break the seal, those little screws are unlikely to hold it ever again.
I would not disturb those screws while afloat, at least not without drilling a small hole in the bottom of the sump to check there's no significant water pressure behind it.
Click to expand...

I see what you mean. Maybe drill a very small hole in the bottom of the sump first.

Bottom of the sump is approx 1.1m below the waterline, so pressure would be 1.1 bar.

- W
 
webcraft said:
I see what you mean. Maybe drill a very small hole in the bottom of the sump first.

Bottom of the sump is approx 1.1m below the waterline, so pressure would be 1.1 bar.

- W
Click to expand...
0.11 bar or 1.5psi.
1 atmosphere is about 10m of water.

It would be good to know from another owner what's under the sump pan and how it connects to the pintles if at all.
But from chatting to people who used to work in the industry, I would not be totally confident that every boat is laminated exactly the same.
Is the ballast only in the front part of the keel?
 
 
webcraft said:
It's not rained significantly in the Algarve for months, and the sump was bone dry before we launched 4 days ago, so it's def. a current leak.

Talcum powder is a good idea!

- W
Click to expand...
Bucket of sea water is nearly as good as rain and plentiful where you are.... ?

Ink
 
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