Annoying Leak.

SiteSurfer

SiteSurfer

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Hi folks.

Just before I commission a rather expensive engine service and inspection I thought I'd ask the assembled panel for any more ideas on a really annoying leak on the boat.
When motoring or sailing water gathers in the engine bilge area (Volvo MD2010/120S) at a rate that requires pumping out every hour (about 6" in the space of approx 3ft square).

This does not occur when stationary. With the exception of rainwater which gathers in the bilge (the engine cover is in the cockpit) - its dry when on the mooring.

I have tried the methods like talc on surfaces and have determined some areas that I subsequently fixed, such as a split in the rudder tube (glassed up), a minor dribble through skeg bolts (replaced and sealed) - have checked the run through from forward (none) and all through hulls (recently replaced all sea cocks and tested dry). One of the thoughts we had was maybe a leak when heeling from deck joints - subsequently not found to be an issue.

I have heard some anecdotes about the water pump in the Volco MD series leaking - I suppose what I'm asking is whether that leak is flipping obvious? I also noted a tiny drip on the exhaust water trap - but cant rationalise that with the seemingly huge amount of water being shipped.

I have checked also things like the cockpit drains and its dry along the whole length of those - and at the through hull point. I am pretty certain that the sail drive gasket is ok - its less than 5 years since replacement and my understanding is that (should it let go) it generally likely to be more than a dribble.

Short of a hole in the hull I'm no sure where else to look, clearly something is causing water to be forced in but for the life of me I cant think of anywhere else to check.

I have checked:
  1. Sea Cocks
  2. Log Fitting
  3. Cockpit Drains
  4. Other through hulls
  5. Keel Bolt areas (they are glassed in)
  6. Rudder Tube
  7. Skeg Bolts

What have I missed? Or is it possible that it is the water pump and I cant see it coming out of the engine in an obvious fashion (not really knowing what to look for)?
 
Last edited:
There is what is known as a witness hole in the body of the pump that only lets water out if the seal inside the pump is leaking. Difficult to see unless you can get down and look at the side of the pump when the engine is running. If the water only collects when the engine is running then it is likely coming from the engine. If it still comes in when the engine is not running then it is leaking through from the outside of the boat.
 
Ah - now that's useful - thanks. It is absolutely more noticeable when motoring, requiring a pump out out every hour. When sailing its very possible I am accounting for water already leaked from the engine after motoring out from the mooring.. You have confirmed that it is entirely possible that with the limited visibility to the water pump its indeed quite possibly the seal, unlike most boats that I have seen the front of my engine is actually the most difficult to get at as its right next to a solid bulkhead.
 
SiteSurfer said:
(about 6" in the space of approx 3ft square).
Click to expand...


That's quite a decent sized leak, I would have thought it was a small stream rather than a drip, so should be easy to spot when the engine is running. Water pump would be prime suspect, assuming shaft seal has been checked and is ok. Could also be a leak on the intake or exhaust anywhere above the waterline. If you are on salt water, i would expect to see salt crystals and obvious water staining/rust marks in the area too.
 
SiteSurfer said:
Just before I commission a rather expensive engine service and inspection I thought I'd ask the assembled panel for any more ideas on a really annoying leak on the boat.
When motoring or sailing water gathers in the engine bilge area (Volvo MD2010/120S) at a rate that requires pumping out every hour (about 6" in the space of approx 3ft square).
Click to expand...

If the leak occurs when the boat is under way with the engine off, it's probably unlikely to be engine-related.

Edit: Now you've given more information, suggesting that the leak is worse whilst motoring, so it could be engine-related. Always good to give full info in your first question if you want sensible answers.
 
Last edited:
pvb said:
If the leak occurs when the boat is under way with the engine off, it's probably unlikely to be engine-related.
Click to expand...

Yeah, but subsequent thinking back over the amount of sailing we actually did last year, its entirely possible that I am muddying the pitch somewhat, given the relative age of the engine and that to my knowledge its not had a water pump seal ever changed - and Tranona's point about it being tricky to see (and that we can't see the face of the engine due to its install) - I may have (at least in part) a reasonable conclusion that it won't hurt to change it anyway.

I can't swear to actually pumping the egine bay out and then testing whilst sailing properly - I've looked usually after motoring in (or whilst motoring) and made an assumption.

EDIT ** Yes - very true. PVB. **
 
I once had to deal with a leaking wet exhaust. The very old stainless steel water trap had succumbed to the corrosive effect of salty exhaust water, and what seemed like a very small drip was slowly filling the bilge sump. We realised there was a problem because the bilge alarm was going off approximately hourly. It required about 30 litres of water to set off the alarm so this tiny drip was actually delivering about a litre every couple of minutes. My point is simply that one should not be deceived by the tiny-ness of a drip if it’s regular.
 
KenMcCulloch said:
I once had to deal with a leaking wet exhaust. The very old stainless steel water trap had succumbed to the corrosive effect of salty exhaust water, and what seemed like a very small drip was slowly filling the bilge sump. We realised there was a problem because the bilge alarm was going off approximately hourly. It required about 30 litres of water to set off the alarm so this tiny drip was actually delivering about a litre every couple of minutes. My point is simply that one should not be deceived by the tiny-ness of a drip if it’s regular.
Click to expand...

Thanks for this, I am beginning to wonder if the combination of (my version) of an inconsequential drip and a possible hidden water pump leak has conspired to provide the issue.
 
In my experience the majority of leaks in boats are via the raw-water pump (or its piping) - next in order of frequency are leaking exhausts, less frequent leaking stern-glands.
As has already been pointed out a drop every 10" is a leak of 18 litres an hour.
I've assumed the OP can confirm the leak is of salt, not fresh water.
If it's fresh water look at the freshwater piping, but first check by turning off the FW pump.
Looks as though he's started at the least likely and is moving, irresistibly to the more likely.
 
Flica said:
In my experience the majority of leaks in boats are via the raw-water pump (or its piping) - next in order of frequency are leaking exhausts, less frequent leaking stern-glands.
As has already been pointed out a drop every 10" is a leak of 18 litres an hour.
I've assumed the OP can confirm the leak is of salt, not fresh water.
If it's fresh water look at the freshwater piping, but first check by turning off the FW pump.
Looks as though he's started at the least likely and is moving, irresistibly to the more likely.
Click to expand...

I took my life in my hands one day and stuck a finger in - its salt water.
 
Tranona said:
There is what is known as a witness hole in the body of the pump that only lets water out if the seal inside the pump is leaking. Difficult to see unless you can get down and look at the side of the pump when the engine is running. If the water only collects when the engine is running then it is likely coming from the engine. If it still comes in when the engine is not running then it is leaking through from the outside of the boat.
Click to expand...

This sounds spot on. I had the same problem with an old Volvo engine. You’d be surprised how much water pours out of that little hole!
 
I'd start by running the engine while tied to a pontoon or quay. First with it in neutral for a while to check for water if none then in gear to eliminate prop shaft seal. If it's only when motoring then it almost has to be engine or prop shaft seal. If you get it running in neutral then it eliminates your shaft seal.
 
Have decided to man up and stop being a total wuss about engines.

I can't see where I can possibly go wrong doing my own service on the damn thing and whilst at it I'll have the water pump shaft out and change the seals too. I've found a replacement water trap too - so will change the whole shebang and exhaust hose and see if that helps - if nothing else it will give me some peace on mind.
 
KenMcCulloch said:
I once had to deal with a leaking wet exhaust. The very old stainless steel water trap had succumbed to the corrosive effect of salty exhaust water, and what seemed like a very small drip was slowly filling the bilge sump. We realised there was a problem because the bilge alarm was going off approximately hourly. It required about 30 litres of water to set off the alarm so this tiny drip was actually delivering about a litre every couple of minutes. My point is simply that one should not be deceived by the tiny-ness of a drip if it’s regular.
Click to expand...

The last major water leak I had turned out to be a porous wet exhaust hose. Changed the hose, a nightmare job, and all was fine.

Richard
 
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