The Blue View - Replacing a Cutlass Bearing

When we hauled Nine of Cups in December, as soon as the power wash was done and all the sea life was removed from her bottom, I took a walk around looking for problems. For the most part, everything looked good – no blisters, the anti-fouling looked depleted but good, no play in, or issues with the rudder. We hadn't run aground since the last haulout, so there wasn't any damage below the waterline. There were several expected maintenance issues, but the only surprise was that the cutlass bearing needed replacing. The cutlass bearing supports the propeller shaft as it exits the hull, and the actual name is a stave bearing. Originally, they were made of the hardwood, lignum vitae, which is resistant to rot, is very hard and doesn't swell when wet. We know of at least one sailboat that replaced their worn cutlass bearing with a locally fabricated hardwood version when the modern equivalent wasn't available, and it worked just fine.

The name 'Cutless' is actually a tradename owned by Duramax Marine for their molded rubber stave bearing. This then evolved to cutlass bearing and became the generic name. I think if I walked into a marine chandlery and asked for a stave bearing, I'd get some puzzled looks – but everyone knows what a cutlass bearing is. For a boat the size of Cups, the bearing consists of a bronze tube with a grooved nitrile, rubber-like lining.

Since it was eight years since we last replaced it, I was half expecting that it might be time again. To determine whether it needed replacing, I took hold of the end of the prop shaft and wiggled it up and down and from side to side. There should be virtually no movement with a good bearing. I was seeing considerable play in the shaft, so I knew it was time for a new bearing.

removing the prop nut

The first step in removing the cutlass bearing is to remove the propeller. It is pressed into place with a large nut and cotter pin. These come off easily, but the prop itself is always reluctant to come free. I remember the first time I tried getting ours off – I spent most of a day prying, heating, tapping and pulling on it before renting a prop puller tool. All boatyards have such a tool, usually homemade, that makes the job quite easy. Here at Power Boats in Trinidad, I couldn't rent just the tool – I had to hire the guys along with it. The cost was higher, but they had the prop off in just a few minutes.

bearing romoved

Next, the prop shaft has to be removed. On Cups, this entails disconnecting the hydraulic piston connected to the rudder, removing the anode on the rudder, then removing the shaft coupler and shaft seal. I also had to remove the pulley for the prop shaft generator. Once these were all loosened and pulled off, the shaft slid right out. I used a scouring pad to clean and polish the shaft.

cleaning the prop shaft

Removing the cutlass bearing itself is next. It is held in place with two set screws and, in theory, once these are removed, the end of the cutlass bearing can be gripped with a pair of vice-grips or pipe wrench and the bearing can be pulled out. If only it were true. We were in Tahiti the last time we replaced it, and I spent two days trying to extract it. I tried all sorts of schemes and finally resorted to cutting it in half, patiently sawing through it with a hacksaw blade. This time I hired the same guys that had the prop puller. They cut through the old bearing in just a few minutes, using a SawzAll fitted with a 10” blade. In order to pull the bearing out, however, they had to perform some surgery to the end of the shaft tube as well.

new bearing

The new bearing was slid into the tube, and I gave it a few taps with a piece of wood and hammer to ensure it was seated. The set screws were screwed into place, and with help from Marcie, the prop shaft was slid back in. It was a tight fit in the new bearing, and lubricating it with a little dishwashing soap and water helped. The rest of the process was the reverse of the removal process.

shaft reattached

The final step was to repair the fiberglass that was cut when the old bearing was being removed. I mixed up a batch of West System epoxy, thickened with 403 filler to about the consistency of peanut butter, and built up and faired the damaged edge. Once it cures, I will sand it, then give it a couple of coats of anti-fouling.

Hopefully, it will be another decade before we have to replace it again.