In pursuit of a dry bilge

We’ve always maintained our boats with minimal bilge water and kept the bilges clean so the engine room doesn’t smell. We check the bilges as part of our regular engine room checks, so we can spot water leaks right way if the level increases, and mechanical leaks are obvious if an oily sheen forms on the bilge water surface. Despite having our previous boat for thirteen years and not finding all the water leaks, neither one of us can figure out why there needs to be an inch of water in the bottom of the bilge.

We have a dripless packless-shaft seal, instead of the conventional stuffing box that drips water by design, so we have no regular drips of water into the bilge. Most are just the minor leaks that occur in most boats. They can be hard to find, however, as many show up only in rough water where we can’t be out investigating the source of the leaks. Still, it seems that we ought to be able to find and fix them all. In measuring the bilge water with a total-dissolved solids (TDS) meter, we found it was a mix of fresh and saltwater. Not all was coming in from the sea–some must be coming in from rainwater or boat washing, as our freshwater tank wasn’t losing any water.

Over the past three weeks, we decided to go after the leaks more seriously to try to get a dry bilge. Here’s what we found:        

  1. The cockput gunnel gangway socket drain runs into bilge        
  2. The cockpit shower door leaks water in rough seas into the starboard aft cockpit locker        
  3. Vents on the starboard aft cockpit locker door leaks water in rough seas       
  4. The hatch from the cockpit to the lazarette leaks a bit of water in rough seas
  5. The propane locker drain hose leaks into the lazaratte at the entry to the locker and at the thru-hull        
  6. The thru-hull for the propane locker drain has no ball valve and plastic connection are in use       

The gangway socket drain accounted for much of the freshwater in the bilge water. Every time rain fell, or we washed the boat, that socket would fill with fresh water that would run into the bilge. But boarding seas would bring saltwater in as well. Instead of draining into the bilge, we installed a small thru-hull in the cockpit below the socket to exhaust into the cockpit.

  

  

To seal the cockpit shower door, we fitted it with insulating foam. We’d already installed a piece of marine board sealed with 5200 marine adhesive over the leaking vents in the cockpit door, but the door is somewhat curved and the marine board had lifted away slightly. So this time we built a gasket from non-skid shelf liner to put between the vents and the marine board, and sealed that with 5200.

  

    

We weren’t bringing much water in through the hatch from the cockpit to the lazarette, and only in heavy seas, but enought to be irritating. Tightening the door didn’t completely solve the problem so we replaced the gasket with a different design. The original was rather rigid and we felt one with a hole through it that could compress more would work better. We’d mentioned this to Don Stabbert, whose boat Starr is docked nearby. Don dropped off a large bag of gasket samples and later a supply of one that we thought we work well. Off came the old gasket and on went the new.

    

    

The propane locker has a drain hose from the bottom of the locker, through the lazarette, and overboard via a thru-hull. This is a safety precaution in case of a propane leak. Tightening the clamps easily resolved the two hose leaks. Replacing that thru-hull was a much bigger job. At minimum we wanted to replace those plastic parts–a Nordhavn had sunk at the dock recently because plastic parts were used in a thru-hull application. But we also wanted a ball-valve to be able to close the thru-hull in an emergency should the pipe break. The existing thru-hull at left was solidly bonded to the hull with 5200, but we eventually managed to remove it by forcibly rotating it in place. We replace it with a new industrial-strength valved thru-hull.

  

We still have a few pieces of equipment that drain into the bilge via hoses and a manifold to a single point: the engine intake drains and the lazarette freezer. These should rarely run water, so we we just put a small bottle on the end of the hose to collect any water that does come through.

  

Beyond the bilge, we also wanted to get our exterior lockers drier. While we had stopped saltwater from entering the lazarette through the propane locker drain, we couldn’t prevent saltwater from entering the locker itself. The drain had to remain open in case of a propane leak, and that meant saltwater could get forced through the hose and into the locker. We also had several lockers where fresh water would get inside, partly from condensation. The lockers drained fine and weren’t really a problem, but we didn’t want their contents sitting in water and wanted to improve aeration so they might dry faster. In these we installed modular floor tiles, cut to fit.

We’ve been checking the bilge regularly, and so far it has remained completely dry for three weeks. This includes an offshore run through Kaiwi Channel to Kane’Ohe Bay on the east side of Oahu, where the cockpit was awash much of the run there.


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6 comments on “In pursuit of a dry bilge
  1. Yes, we are a dry exhaust boat as well. We have 5 water intakes on Dirona: 1) house raw water pump, 2) hydraulic cooling, 3) wing cooling, 4) generator cooling, and 5) water maker. The first 4 are down in the main bilge and one is behind the generator. Any of them in the main bilge can vent the PSS. Ours is hooked up to the house raw water inlet.

    –jrh

  2. Doug says:

    James,

    I would like to install PSS seals in our 47. We had them in our sportfish and loved them. You mentioned that the venting hose from the seal was connected "to the raw water intake". Since you are dry exhaust, I assume like us, what raw water intake did you plumb it to. I see in the picture the hose, but I can’t tell what exactly you plumbed it to. Can you plumb it to any raw water intake, generator, watermaker, wing engine, etc. since it really is only acting as a vent? I would appreciate any information you can provide.

    Thanks. Doug

  3. Doug asked "what is the source [for the dripless shaft seal cooling water] that is available 100% of the time." It is a dry exhaust boat so its a good question. The PSS installation instructions only require a water source on boats that run faster than 12 kts so this is not a requirement.

    From: http://www.shaftseal.com/en/about/installation_instructions
    ——
    15. Plumbing the system:
    15A. Low speed boats:(Under 12 knots of boat speed under power).
    Note:Sailboats or displacement powerboats with a powering speed below 12 knots can use either method A or B.

    Using a 3/8 ” ((8 or 9 mm)ID “underwater rated ” hose ((not provided with the PSS), connect the hose to the hose barb fitting installed on the carbon and secure the hose with two (2)hose clamps.Run the hose to a point in the boat at least two (2)feet above the waterline,making sure that the hose does not apply any load on the carbon part of the seal.Keep the hose as close as possible to the centerline of the vessel so the top of the vent hose is never below the waterline,even if the boat heels.Secure the hose in place with the necessary fittings that insure it will not pull free and drop.This hose is now a venting hose that will help ensure that no air is trapped in the seal.
    ——–
    I talked to PSS on this specific installation and they confirmed that a water source was not required. They recommended connecting the cooling water hose to the raw water intake so that air could bleed out when the boat is returned to the water. And, if there is any low pressure pulled in the shaft seal area by the hull passing through the water, this would relieve it. You can see this hose in the top picture above. It enters from the right side of the picture and connects to the raw water intake. There is no pump and no pressure water supplied to the PSS.

    –James Hamilton

  4. Doug says:

    Where do you get the water from for your dripless shaft seal? Do you have wet exhaust? If not, what is the source that is available 100 percent of the time when the engine is running?

  5. Thanks Eric. We appreciate the feedback.

    –jrh

  6. Eric Meslow says:

    Great information and I love the detail of your blogs.

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