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July 2020

Do Not Tease the Cutlass Bearing

Back in the 1980s there appeared a few articles in Yacht Racing & Cruising (and later Sailing World) under the name Ebon Bilgewater, a determined and sometimes hapless young sailorman. This is a slightly updated version of one originally called “Beating the Bushing.” Reprinted by permission.

Anyone who has spent some time around auxiliary sailboats will be familiar with the curious sensations generated by a worn cutlass bearing: a deep, low buzzing in the ears, as if a giant mosquito were hovering nearby, and a tingling numbness in the legs akin to what is felt by some motel visitors after standing on their Vibro-Beds for several hours. The numbness is most noticeable while motoring through a glassy calm with a hot sun beating down relentlessly overhead.

The trade name is Cutless, but most people call the innocent-looking part a cutlass bearing. Photo courtesy of Johnson/Duramax

 The more worn the bearing, the more intense the sensations: In yawls and ketches with neglected bearings, watching the mizzen shrouds vibrate for more than a few seconds will induce optical illusions and nausea. So it is both a seamanlike and medically sound practice to change cutlass bearings when they become worn; and, as in everything else, there is both a right way and a wrong way to do it.

Before getting into procedures, a word about the cutlass bearing itself is in order. First, the proper term for the item is "stern bushing" or "stern tube bearing." But even more proper, if you’re a boat-parts purist, is calling it a cutLESS bearing, because Cutless is a trade-name for the stern bushing made by a particular company. However, the word “cutlass” is widely used, especially because experiences with this particular boat part remind us that a cutlass is a type of sword, habitually used by pirates to hack innocent seafarers into tiny, indiscriminate pieces.

The bearing sometimes lives in a strut; sometimes, logically enough, in a stern tube projecting below the boat or embedded in the trailing edge of a keel. What it bears is the propeller shaft, which first comes out of the engine's transmission and then goes through the stuffing box. The cutlass bearing is the last thing that holds the shaft on its way to the propeller. Theoretically, the shaft makes its way through the bearing straight and true; the clearances between shaft and bearing are minute and precise. No matter how well-aligned the shaft, though, within a certain number of years it will wear down that bearing surface and start to bounce around at a high frequency, thus causing the medical problems referred to earlier.

Cutlass bearings have traditionally been made chiefly of brass or other composition metals like monel, which is an alloy of mostly nickel and copper, used extensively for marine propellers and shafting. The bearing surfaces used to be made of lignum vitae; now they're usually vulcanized rubber, arranged in longitudinal grooves that lightly hold the shaft and allow water to flow in and out as far as the stuffing box for cooling and lubrication. Some cutlass bearings today are made entirely of plastic, so that inserting and removing them is simply a matter of adjusting their temperature (by refrigeration or subtle use of a torch or hair dryer) to let them expand into or contract out of tight places.

The cutlass bearing here lives in the projection of the stern tube outside the keel. Note the painted-over set screw. Doug Logan photo.

 The cutlass bearing to which I am referring in this cautionary tale is one of the older variety: It is to the all-plastic bearing what Ahab, at the height of his monomaniacal fury, is to Skipper, of Gilligan's Island.

Problem: You have just bought a used displacement sailboat. In the surveyor's glowing report, there is one sentence that disturbs you: "Cutlass bearing needs replacement ASAP." You sail the boat for a full season, and whenever you run the engine, you worry. Gradually,you begin to hear the giant, invisible mosquito. Little by little, the vibration of the cockpit sole takes hold of your psyche, until, as the first golden leaves of autumn drift down into your anchorage, you resolve to haul early and have at the bearing, before it causes a problem. You haul and block the boat, remove the prop, loosen the shaft at transmission, slide the shaft easily from engine, and stare haughtily at the naked interior of the cutlass bearing. Now, all you have to do is remove it.

If your cutlass bearing lives in a strut outside the hull, you’re in luck. You can skip all 12 steps in the next section and go directly to the conclusion: “The Right Way: Three Easy Steps.”

The Wrong Way: 12 Easy Steps

  1. You understand that the cutlass bearing has been embedded in the aft end of your keel for 14 years, and that it is likely to be a bit recalcitrant about coming out. All right, then, the first thing you will have to do is remove the set screw that (you think) keeps it in place. The screw might be in the side of the external strut, or in the keel at the side of the bearing, or inside the boat, aft of the stuffing box somewhere in the stern tube. It will probably be painted over, or stripped, or both. Also, if it’s inside the boat there will be tankage, or plumbing, or some engine or cockpit part that will prevent you from turning your hex wrench or screwdriver more than a twitch at a time. (If the screw is not already stripped, go ahead and strip it; get that step out of the way. Maybe you can get hold of enough of it with Vice-Grips to move it, or if that doesn’t work, hit your Vice-Grips with a hammer. You didn’t like those Vise-Grips anyway. Or just face the music and drill it out. You can tap a new set of threads before you put in the new bearing.)
  2. Next, listen to some pundit tell you that a bearing can be knocked out with a dowel or a piece of pipe of a bit smaller diameter. If you are foolish enough to try to tap the bearing out with a dinky little hammer and a broomstick handle held against the bearing, and find that it doesn't work, you will probably be foolish enough to think a little more force is necessary. In that case, the best thing to do is go and get the jack of your foreign car, place it between your engine transmission and the cutlass bearing, and crank it right up.
  3. After you have put the remnants of your automobile jack in an appropriate receptacle, you will probably want to lose your temper, go to the hardware store, and buy a four-ton hydraulic jack. By all means, do so. They're surprisingly inexpensive, and pack quite a wallop.
  4. Place your new hydraulic jack between your engine transmission and the cutlass bearing, using all sorts of blocking materials and galvanized pipes in between. You will be dimly aware that you are skating on very thin ice over very deep water. It will be exciting. Go for it.
  5. As you pump up the pressure on the hydraulic jack, and near its maximum capacity, you will begin to hear creaking and moaning in the boat. You will be tempted to pay attention to these sounds. You may even think that the boat is trying to tell you something, like: Stop. The bearing isn't going to move. Quit bothering it, or you’ll be sorry. But you won't listen to the boat, will you? No, you are quite sure you've got all the angles covered.
  6. Sooner or later you will reach a point where you will want to give the jack One More Little Pump. By now things are very exciting, with strange and exotic sounds coming from everywhere. You know the bearing has to give, and you know it will be on the next stroke. Oh boy. You can hardly wait. Just to be on the safe side, though, remove yourself from the area and do that last stroke by remote control. Tie a piece of flag halyard to the jack handle. Take off the doors or hatch to the engine compartment, lead the flag halyard over the top of the engine, and pull the pump handle in the comfort of your main cabin.
  7. You have now pulled the handle that extra stroke. You have heard even more strange and portentous sounds, but, as you cringe your way back to inspect the bearing, you find that it hasn't budged. You're good and mad now, aren't you? Go ahead, show that bearing a thing or two. Give it the Old What For.
  8. For the Old What For you will want to be fully braced, knees bent, feet wedged against something solid, hands holding the length of flag halyard in a pose which, if the flag halyard weren't there, would remind an onlooker of a late 19th-century pugilist.
  9. Now begin your last Herculean tug. The creaking and groaning will resume. Increase tension. The cords in your neck will stand out like the striated vertical ridges on the slopes of a brewing volcano. Your fingers, wrapped by turns of a stretching, humming polyester boa constrictor, will turn a royal maroon. You will probably want to grit your teeth and grunt something like, "Come on, you little...," and more to the effect that if the cutlass bearing doesn't move, you will somehow punish it severely. What you don't realize, and you will understand quickly in hindsight, is that it is impossible to intimidate a cutlass bearing.
  10. At some point during the Old What For you will hear a loud noise; a giant cracking, clapping sound, much like what you would hear if you happened to be standing near a sequoia when it was snapped off halfway up the trunk. The flag halyard in your hands will go slack, and simultaneously you will punch yourself in the nose. You will then fall backwards into your companionway ladder, which will shatter like a prop in a Three Stooges gag.
  11. Now you can pick yourself up off the cabin sole. Your ears will be ringing, but you can be thoroughly pleased with yourself. Judging from the sonic boom, the cutlass bearing has emerged from the stern tube at Mach+ speed, flown through the chain link fence of the boatyard, and landed at the far side of a neighboring parking lot. 
  12. Check your work. Remove the jack and all blocking materials from the bilge where they have fallen. Look down the stern tube. The cutlass bearing is still there, is it not? Now look behind you. Your two aft engine mounts are sheared off, are they not? And the transmission is now resting directly on the turn of the bilge. What a nuisance.

The Right Way: Three Easy Steps

  1. Find yourself a comfortable stool, or a boat cushion will do. Place it on the ground near where the cutlass bearing is located in your keel or strut. Sit down.
  2. Take a new hacksaw blade, wrap one end of it in a rag so you won't hurt your hand, insert it in the cutlass bearing, and begin sawing. Saw for quite a while, until you’re through to the stern tube all along the bearing.
  3. Take another new hacksaw blade, begin at a point about 90 degrees away from your first cut, and saw for another long time. At some point during your session, the cutlass bearing will slip from the stern tube like a jellybean from the mouth of a child, and land in your lap. This may hurt, but you should be glad of the pain.

Ebon Bilgewater is Ambrosia Bilgewater's brother.