A Mystery Leak / looking for ideas

[PlumBob]

We have a leak - that we can't find - here's the scenario.....

After sailing - specifically, after motoring - we take on water into the bilge. The bilge pump will come on about an hour after we get in, and most often, again a couple of hours after that. Occasionally, at other odd times, but not with any regularity, like after motoring.

The prop shaft packing gland is dry. Sometimes it will be moist, but not ever "wet." The same with the rudder post packing gland.

All thru-hulls are tight and dry. There is no water coming down the center of the boat from the anchor locker to the bilge (in the stern.)

The water heater is not leaking, nor any pressurized water leaks (any of which would run down the center of the boat.)

All the thru-hulls in the transom are dry - cockpit drains, exhaust, etc.

The raw-water intake seacock is dry and there are no apparent leaks in the engine cooling system.

The walls of the bilge are dry, down to water level.

I've done everything except lay there on my belly and watch for 2 hours, to see if I can see where water may be coming in. It's not that I mind having water in the bilge, mind you - but I would like to know where it's coming from...

What am I missing here? Thoughts?

All comments appreciated!

[Brighteyes]

I had the identical problem, nearly drove me mad! It turned out to be a pinhole in one of the pipes to the calorifier. Under pressure a thin stream of water came out, hit an electrical loom and dripped down into the bilge. I only found the leak by using a torch, the leak was almost impossible to see as the jet of water was very thin. Start your engine then go over every inch of the calorifier pipes with a torch. Good luck.

[J_m]

Do you have a check valve in your bilge pump hose? If so the vibration of motoring ( or rocking of sailing) may be causing whatever water is in your hose above the check valve to flow (leak) back into the bilge through the bilge pump -- and when water sloshes around enough -- it triggers the bilge pump to go back on. Just a thought.

[Ocean Girl]

Do you have a propane locker that vents out hull?

We are a psc34, previous owner drilled a hole to run cable into boat from propane locker. When she motors her stern squats and a little water comes in, since the PO put the hole for cable at bottom, the seawater drips into the bilge. Genius I know.

[Vasco]

It would help if we knew what make of boat we're talking about. Over the years you get to know what part of which make of boats leak. For example I'm aware of certain leaks that are peculiar to Beneteaus. Also, it is salt or fresh?

[JPA Cate]

I think Brighteyes is on the right track here: what you may be looking for is a leak that occurs only when there is water pressure. If that hypothesis is correct, then anywhere on the system that is pressurized may have a pinhole leak. We had one on our exhaust elbow that took a while to find. In our experience, the exhaust hoses, being extremely heavy duty, are less likely, but we've all known split hoses to occur at times.

[Vasco]

Or there might be a leak somewhere around the transom that occurs when the boat squats when motoring.

[Capt.Don]

Check the anchor locker drain holes - we had a large gap inside the hole between the locker and the hull, allowing water to flow down along the inside hull to bilge. Simple fix - mix thickened West Systems- voila - no more leak and dry bilge!

[ranger58sb]

1) Salt water or fresh?

2) Sometimes you can spread something like flour or baking soda or laundry detergent powder around to locate water ingestion tracks.

-Chris

[PlumBob]

Originally Posted by Vasco

It would help if we knew what make of boat we're talking about.

Sorry, I thought it showed up... Island Packet 32 - (#102)... In freshwater. But the boat lived the first 18 years of its life in Puget Sound.

[neilpride]

Originally Posted by J_m

Do you have a check valve in your bilge pump hose? If so the vibration of motoring ( or rocking of sailing) may be causing whatever water is in your hose above the check valve to flow (leak) back into the bilge through the bilge pump -- and when water sloshes around enough -- it triggers the bilge pump to go back on. Just a thought.

+1 I got this same problem time agoo, bilge dry, if we sail and heel , water flow back to the bilge , the check valve is just few inches after the pump , we fix it changing the check valve and making a hig loop at the hose truhullside area...

Taste it if is fresh or salt water, a stufing box could be dry at your eyes , but motoring cause some vibrations maybe and some leaking is posible...

With a spotlight at hand , run the engine with some one at the wheel and go here and there , engine room as you say it happen after motoring...

[Suijin]

Originally Posted by PlumBob

The prop shaft packing gland is dry. Sometimes it will be moist, but not ever "wet." The same with the rudder post packing gland.

The prop shaft gland would be the first thing I check closely simply because they should drip and they often require adjustment to find the right balance of seal vs. heat.

Have you checked it while the transmission is engaged, and actually lay down and watched it? If you're only checking it after you've shut the engine off, it's possible that it has dried by the time you eyeball it given that it gets fairly warm during operation. You can have fairly significant water ingress and if you're not actually watching it, the "traces" of that leak could all but vanish if you check it a few minutes later.

That said, the leaking should stop for the most part when you shut the engine off (or put it in neutral). The fact that the pump comes on an hour later is telling me that some pressurized part of the system is responsible...the leak is likely continuing as the system cools down. I agree that calorifier is the first thing I'd investigate closely.

And with leaks like this, yes, you probably do need to lay down for an hour or so and see what you can find. If you're in a slip, just idle the motor and throw it in forward and get in there with a good flashlight.

[PlumBob]

I don't think I have a check valve in the bilge pump hose - not absolutely sure - but I've looked over that entire line and I don't think there is anything between the outlet on the transom and the pump itself. There is a strainer on the inlet side - it's dry.

Same thing with the propane locker - I've looked it over, but not with a microscope. I guess I will have to.

The anchor locker, I believe, can be counted out. It drains to an under-floor "raceway" that goes the entire length of the boat, bow to stern, and water from the anchor locker flows down this to the bilge. This raceway is dry. That said, it is accessible in several places, so I will drop some flour in and watch for runs. Leaks at the deck-to-hull joints, stanchions, chain plates, etc. would drain to this raceway, too.

So I guess that really does bring me to leaks that happen under pressure - presumably from heat. So I'll lay there flashlight in hand, both under way and after, and see what I see... Oh My.

Great responses - Thank You All.....

Other thoughts?

PB

[pbiJim]

Cut some pieces of cardboard the shape of your lower bilge & duct tape them into place to form baffles along the bottom of the bilge. Then look to see which baffle sections get wet & which ones stay dry. That should point you to the correct general area.

[Cheechako]

try laying toilet paper around any area where water may run to the bilge right after sailing or motoring. Then check an hour or two later and look for any wet paper...
I like the pressure idea... amazing how hard it can be to see a pinhole stream that is directed right toward the block behind something. I guess running your hand or some paper under the engine pan should tell you this though....