Episode 32 - Diesel engine Part 3 - Interrupted by water

The scariest thing about this project is not knowing quite everything about what keeps water out of the boat.

The glass reinforced plastic (GRP) hull is easy, and the stopcocks are not difficult to figure out. The shaft seal, however, was a mystery. It turns out that that the type of seal on my boat is a PSS Shaft Seal, installed when I replaced the shaft and prop in 2019. Normally, access to the seal is by the usual contortions and boat yoga performed over the engine, which is not designed to comfortably bear your full body weight, transmitted through the softer regions of your belly, whilst you try to get your hands to the seal.

The PSS Shaft Seal website has an interesting graphic that tells most, but not all, of the story. What is not immediately obvious to the uninitiated is that the bellows (the black wriggly rubbery section) are fixed to the boat and all they do is push the sealing ring (the part with the small pipe coming out of it) against the stainless steel collar (to the right of the assemblies shown on the website). The stainless steel collar is fixed to the prop shaft which, of course, rotates. The joint between the sealing ring and stainless steel collar keeps the water out of the boat.

The pressure holding the sealing ring against the stainless steel collar is quite light; it only needs to resist about 0.3m (1 ft) of water pressure, so it does not need a lot of pressure to keep the water out. It is not difficult to dislodge (I’ll return to that, shortly), but is usually kept safely in position by the engine. 

Another important feature is the small tube coming out of the side of the sealing ring. This is to allow air in the seal to be “burped” out, by squeezing the bellows. If you don’t “burp” the seal, it will drip. An air bubble in the seal is enough to crack open the joint between the sealing ring and stainless steel collar. You need to burp the seal every time you put take the boat back into the water, or it will drip.

With no engine to keep things in place, the shaft is vulnerable to getting knocked about, especially when you are trying to cut away engine beds with a demolition saw in close proximity. Many times, I dislodged the seal, letting water in, but it was relatively quick and easy to re-seal it with a bit of a wiggle. 

Religiously, or so I thought, I would not leave the boat unless I was satisfied that the seal had been seated nicely so that it would not leak in my absence. I even devised a little cradle for the prop shaft so that it was not resting on the bottom surface of the shaft tube. The timber got painted red from my engine-part respraying exploits, and you can see it in some of the photos under the prop flange.

However, alas, I either let my guard down, or something happened in my absence to dislodge the seal. I left the boat on Friday afternoon, confident that it would stay dry, and got a call from the marina on Tuesday morning to say that the boat was taking on water and was lying about 1 foot lower than it should. Phil from the marina politely asked if he could open the boat to drop a couple of pumps in there to pump it out. Politely, I responded yes please, and privately started to worry about where the water was coming from, and whether I should try to get the boat on the slip (which was closed for Christmas) in a hurry.

As I live only about half an hour from the Marina, and was working from home, I clocked off for lunch and hied on down there as fast as the legal road speed limits would allow. The pumps had done their job and the boat did not sink. It was wet, though, and the prime suspect, a the dislodged shaft seal, was burbling away merrily, trying to sink the boat anew. With a bit of a wiggle, I re-seated the seal and set about cleaning the boat (again) and mopping out the bilge (again) and wondering if I should get an automated bilge pump, and where I could possibly put it. I did not dare to switch on the electrics, but it is possible that the water reached to the lowest of the switches in my switch panels. I remembered that my surveyor had mentioned something about the disadvantages of having switch panels mounted low down. I will need to rewire the engine connections in any case, and this water ingress might precipitate a more comprehensive rewiring project.

Phil suggested I put some tape around the seal to keep it safe. One of the advantages of volunteering with the SES is that you learn some useful stuff, like what tape is useful for what. In this case, I did not want something that stuck like superglue to the more rubbery parts of the seal, because it might damage it when I pulled it off. In any case, residual glue on the parts would attract dirt and the ever-present boat-crumbs that seem to spontaneously regenerate in the bilge. I needed something that was moderately water-proof and that would not stick to anything but itself. The worst solution was gaffer tape; the best duct tape. Fortunately, I had a small roll of duct tape at home, and dutifully applied it to the seal. I checked the boat over the next couple of days and was glad to see it bone dry (again). I also removed all the clutter I had left in the boat, including all the cushions, to take them home to dry them. In the process, I found some lockers that I did not know I had, and some stuff in the lockers that I did not know I had, including a spare jib-track car. I had previously tried, and failed, to find a replacement for the broken one on deck, and had started to buy the (expensive) parts to replace not just the cars, but the tracks also, because the new cars do not fit the old tracks. In the end I gave up, returned the parts to the shops I had bought them from, and set a block up on the toe rail for the jib sheet as a jury-rig.

There are some lessons to be learned here;

• Berthing in a marina is expensive, but cheaper than finding out that your boat has sunk while you were away. I am very grateful to Phil and the others at the marina for keeping an eye on my boat and all the others in the absence of their owners.
• When doing major surgery to your boat, it is a good idea to empty it of everything that is not screwed down. I had to get everything out for a clean and a dry part way through the project, and might have made life easier for myself by doing it at the start. It would have meant less cleaning, especially to the cushions and other soft bits and pieces, such as the life-jackets.
• If your shaft seal is dangling around in mid-air, secure it with a little chair and tape it up with duct tape.

Finally, I will probably get an automated bilge pump. The question is not about expense - the cheaper ones are about $50. The question, in my case, is that the bilge is so shallow that there is not enough headroom under the floorboards to get an off-the-shelf pump in there. The maximum headroom under the floorboards is just about a hand-breadth (not including my thumb), or about 80mm, which is less than the 125mm needed for the smallest pump units. Possible solutions are a pump with a remote sensor and suction tube (not available off-the-shelf), or taking out a section of the cabin sole in the engine compartment under the cowling, or cover, that sits over the engine. Another conundrum to solve, and the list just gets longer!

Phil from the marina took this photo after he had started to pump the boat out