Boatworks

The forgotten details

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I often hear from people who, after years of preparation, have set out on their first ocean crossing with a high degree of confidence in their boats. Then something really disconcerting happens—say, the propeller shaft disappears out of the back of the boat. It’s quite a confidence shaker. I’ve heard enough of these stories to be able to identify several easily prevented but potentially catastrophic mishaps. Here are 10 items to add to your commissioning schedule; they’re probably below your radar, but they could save you a great deal of trouble.

1. Check that the propeller shaft is firmly attached to its coupling. If the shaft comes loose when the engine is in reverse, or even when the engine is shut down and you are under sail, it may be sucked out of the back of the boat. If it is not blocked by the rudder before pulling all the way out, you will suddenly be faced with a round hole that has the potential to flood your boat at a truly alarming rate.

If the shaft is held in its coupling by a set-screw, make sure the screw is seated in a drilled recess in the shaft (you will need to take the screw out to check for this; if there’s no recess, you can drill one, but take care not to mess up the threads in the coupling). The set screw needs to be secured with locking wire. Better yet, drill through the coupling and shaft and add a through bolt with a Nyloc nut to ensure it won’t vibrate loose. This way the shaft will never come loose. Finally, install a spare shaft zinc, or a hose clamp, around the shaft just in front of the stuffing box or shaft seal. If the shaft does come loose, it won’t be able to slip out the back of the boat.


2. Look closely at the rudder stock where it exits the bottom of the boat. On modern boats many rudder stocks are made of aluminum, which can corrode rapidly, causing the loss of the rudder. Unfortunately, this seems to be an increasingly common event. If you’re worried about your rudder stock, remove the rudder and inspect it. Some aluminum rudder stocks, like those from the Danish company Jefa, are designed to be galvanically isolated from the rest of the boat. If this galvanic isolation is accidentally violated (which is easy to do, for example, when installing an autopilot), the stock can corrode quite rapidly. If you have a multimeter and know how to use it, you can test for galvanic isolation by putting the meter in the ohms mode and testing with its probes from the rudder stock to the engine block or any other metal wired back to battery negative. The multimeter should show infinite ohms (no circuit). If the rudder stock is bonded instead of isolated, you should read very low ohms to the bonding circuit. In this case, be sure to regularly renew the zinc anodes on the outside of the hull and check that the circuit between them and the rudder stock is very low resistance (less than 1 ohm). Because a zinc’s effectiveness is directly related to its surface area, they should be replaced when they are no more than half consumed.

3. Stainless-steel chainplates are always suspect. Moisture can collect in any place where chainplates pass through a deck or are bonded into the boat. In the absence of a fresh supply of air, deoxygenated moisture can rapidly corrode stainless steel, resulting in chainplates that can eventually fail without warning.

Unfortunately, the chainplates are often buried behind cabinets and liners, but they really should be removed and inspected on older boats before an ocean crossing. And, just because one comes up clean there’s no guarantee the others are okay; you need to look at all of them. Hopefully the boatbuilder will have made the chainplates accessible, but unfortunately many do not.


4. Check your roller-reefing forestay. Forestay failure on boats with roller-reefing headsails used to be more common than it is now. Furling units are also much more reliable. The problems that do arise are almost always caused by the halyard wrapping around the forestay or by the roller-reefing line snarling up on the drum when the sail is let out. New units may work fine, but once the bearings are a little worn or there’s some dirt in there, the system can foul up, generally at times when you least want it to. To avoid trouble, the halyard must either angle away from the forestay at 10 degrees or more or must have an anti-wrap device. The reefing line must run onto the reefing drum at a 90-degree angle.

5. Clean your fuel tank. Over time, sediment in the fuel settles to the bottom of the tank. The engine’s pick-up line is set an inch or two above the bottom of the tank, so the sediment normally goes unnoticed. But when the boat gets into turbulent seas, the sediment is stirred up and can get sucked into the fuel filters and plug them up while the engine is running. At best, the engine will lose power and maybe die. At worst, the fuel filters may rupture under the suction pressure from the lift pump, flooding the injection system with the dirt from the tank, and causing serious damage to the engine.

It is important to periodically clean out the fuel tank, down to its lowest point, especially on an older boat. If there is no access to the tank’s interior, then access must be created. Keeping the tank clean will also help limit algae growth in the fuel. Algae can live in the interface between diesel and water. If you keep water out of your tank, you will not get algae. If you keep your tank clean, your fuel filters will always look clean when you change them. The corollary is that if your filters are dirty, you urgently need to clean your tank.

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