What You Dont Know CAN Hurt You

By Tom Neale, 4/14/2011


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You never know what sneaky little issues are developing on your boat that can rise up out of the dark and bite you on your backside. This is true for just about any part of the boat, but it’s what may be going on under water that really gives me concern.

We’ve just splashed after yet another haulout at Camachee Island Yacht Yard in St. Augustine FL (www.camacheeisland.com/camachee-cove-yacht-harbor). I always dread haulouts because of the cost, the hassle, (I hate living aboard on the hard and now seldom do) and what they may turn up. Also, I feel like I’ve lost my freedom when my boat is landlocked. I avoid haulouts as much as I can by regularly diving the bottom and checking things out. I also use Interlux Ultra anti fouling paint which I think is a great product. But you’ve got to have those haoulouts because the world is far from benign down there. This past one, as it turns out, saved me some money—much more than the money I save on diesel fuel because of a clean bottom.

Scrap of Monofilament Almost Ruined Thruster
I have bow thrusters. Wouldn’t be without them in a boat like mine. (She’s a single screw, long keel very heavy 53’ motor sailer.) Just a few barnacles or oysters or clams growing in the tunnel or on the propellers will substantially impair the performance of thrusters. I check them out while diving and knock off what I can with a long screwdriver, but there isn’t clearance between the ends of the propeller blades and the tunnel walls for me to do much behind the blades. So each haulout the propellers get pulled and cleaned. The tunnel is also cleaned and sanded and everything is painted. This year after the blades were pulled, the yard owner happened to be walking by and looked into the tunnel to check out the job. He saw oil seeping from one of the shaft seals. (At first, when the propellers had been pulled, it wasn’t noticeable because it was a slow leak.) Later there was a puddle of oil on the bottom of the tunnel and it was milky. This means oil and water mixed.

In my thrusters the gear box, which is outside the boat and in the tunnel, is kept full of clean oil by gravity feed through a clear tube running from a reservoir inside the boat. You watch the reservoir for losing or gaining oil and for oil discoloration. Depending on the water pressure on the seals, the amount of time you use the unit and other factors, it’s hard to say, without the experience of having a thruster failure, whether a bad seal will increase or decrease the level of oil in the reservoir. My level had not changed and there was no sign of milkiness in it, so all appeared to be fine. But not so.

Clearly, seawater had leaked past the seals into the gear box when the boat was in the water. Without that water pressure the fluid had run out past the seals and notified us of the problem. But fortunately, there was no sign of milky oil even in the tube entering the top of the gearbox. This meant that the problem hadn’t been there long and there should be no damage to the gears from running in oil/salt water. The gears are robust and don’t have the intricacies of, say, a transmission. But some sea water had gotten in there and it would have continued over time until a problem occurred, possibly without my ever knowing it was happening. By the time I noticed something unusual in the reservoir or feed tube it may have been too late. I would never have seen this little leak on my regular dives.

Vern Making Sure All is Well as Del Lowers Away
I was unhappy at the problem but very happy that it was discovered. The new seals cost around five bucks apiece and were in stock. But that wasn’t the end of this story of unseen problems.

The guy who changed the seals, “Del,” knows his stuff. I’ve appreciated his help before. I’ve also appreciated and written about the “Del and Vern Show.” These two guys can handle a boat getting into and out of tight spots (such as haulout facilities) like magic. Only one seal was leaking, but obviously I had both changed because I figured the problem was associated with old age and the other might soon follow. But when Del pulled out the bad seal he noticed something there besides the seal. It was a very fine somewhat mutilated piece of plastic monofilament--that stuff that’s good for fishing but bad for so many other things. It was caught up in the seal. I have no clue how this happened, except to assume that one time when I was operating the thrusters a little piece was floating in the water and got sucked in by the thruster and then, simply from bum luck, got wrapped around the shaft and worked its way into the seal. The bottom line is that if I hadn’t gotten the boat hauled then, and if there hadn’t been an observant yard operator, and if the guy replacing the shaft hadn’t also been observant, I would maybe be looking at another haulout and another set of gears for my thruster, pretty soon down the road. And worse, I might have had a thruster failure at the worst possible of times and done some other damage to my boat and maybe others.

There are other things that only a haulout will reveal. For example, monofilament around the shaft working into the cutlass bearing—a very expensive repair if you don’t catch it. Another example is oysters, clams and barnacles growing up in those through hull intakes. It’s been my observation that usually this doesn’t happen, I suppose because there isn’t much food floating by except when that engine or air conditioner is sucking in water and then it’s probably floating by too fast. It’s more likely to happen with a sink or some other kind of drain. But in that situation you just experience a slow diminution of outflow. When the critters make a home in an engine raw water intake you may not notice the slightly diminishing flow as they grow. At first, your engine may not notice it and may not overheat. But your impellor will notice and eventually will start to self destruct on a regular basis. I know one guy who changed his impellor repeatedly and then his water pump twice because he thought something was wrong with “his impellor eating piece of ……” Only later did he find that the pump wasn’t getting the water it needed because a fat clam way up inside the intake had been getting fatter and fatter. Unless the critter lies on the outer limits of the through hull, you won’t see it until you haul out and take a look. Often this involves removing the outside strainer.

So I’ve just suffered through the trauma of another haulout, but I’m very glad I did and, in the long run, will probably have a little more money to buy diesel fuel.

Tom’s Tips About Removing Exterior Strainers

1. Removing exterior through hull strainers can present serious issues, but, nevertheless, they should be removed periodically so that they and the through hull can be cleaned inside and painted with a coating appropriate to the metal surface.

2. These are usually screwed into the hull. Fiberglass hulls can only take so many screwings and unscrewings before the hull begins to break down around the holes making it difficult for the screws to bite.

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