S/V Blue Teal, Alberg 30 #285 -- Mechanical Propulsion

From: David Fay
Sent: Tuesday, January 29, 2019 6:22 PM
To: Alberg 30 Public List -- open to all
Cc: Gerard Kuperus
Subject: Re: [Public-List] stern tube question

Having just done replaced my cutless bearing, I can provide you with some guidance. I decided to replace my bearing when a friend pointed out to me, after my boat was hauled this past fall, that he could wiggle my prop shaft (maybe a 1/4" of play). He recommended that I replace the bearing and, since he builds drive trains for the new Zumwalt-class destroyers at Bath Iron Works, I tend to listen to him (about drivetrains anyway)

Here are the steps I followed:

1. Remove the nuts holding your prop on.
2. Borrow a prop puller, or improvise one, and pull your propeller off. Don't lose the key that fits in the keyway and keeps the prop from rotating on its shaft.
   I have a three blade prop and it took some gymnastics to get it past the rudder. At one point I thought I was going to have to remove the rudder, but I finally found a combination of rudder angle and prop rotation that did the trick.
3. Remove the cutless bearing housing, which includes the cutless bearing. This is bolted to the trailing edge of the hull with two bolts and also screwed on to the stern tube. The first step is to remove the two bolts holding the housing to the hull. The next step is to unscrew the housing from the stern tube. However, the stern tube is just floating in caulk (thiokol, unless it has been modified) so nothing prevents it from rotating when you try to unscrew the housing. So put a pipe wrench on the interior end of the stern tube and wedge it against the hull or have a helper hold it so you can unscrew the housing without rotating the stern tube. My housing came off with no trouble once the stern tube was immobilized but it had been removed just five years ago when my engine and prop shaft were replaced. I can imagine that it might be hard to unscrew if it hasn't been touched in decades.
4. Now you need to remove the cutless bearing from the housing. The first thing to do is remove the two set screws that keep the cutless bearing from rotating. The set screws have hex socket heads so you need an Allen wrench to get them out. But both of the heads were stripped so I couldn't get the set screws out. Ultimately, I had to drill the set screws out, redrill the holes to a larger size, and tap new threads in the holes. I ordered 18-8 stainless steel cup point set screws from McMaster-Carr (3/8"-16 thread, 1/4" long, $4.57 for a pack of 25) as replacements and they worked fine. I went back and forth about whether I should coat the threads with Tef-Gel to fight galvanic corrosion (stainless steel set screws in bronze housing) or Loc-Tite to keep them from backing out (the originals had been scored with a metal punch once they were in place so they wouldn't rotate). I still haven't made up my mind about that but I'll probably go with Loc-Tite.
5. Once you've removed the set screws you need to get the old cutless bearing out. That proved to be the hardest step for me. The basic idea is to cut the bearing from the inside with a hacksaw blade in one or more places to relieve the pressure fit and then to collapse the bearing onto itself. It's hard to make a good cut through the bearing material (a brass shell surrounding a rubber interior) because the forward end of the bearing butts up against the threads that screw on to the stern tube and you really don't want to wreck them. Fortunately, someone had cut a path through the threads on my housing, so that made it easier to cut the bearing. But one cut wasn't enough because the bearing still wouldn't come out. So I cut it in another place. Still wouldn't come out. Then I tried pushing the bearing in through the set screw hole and it began to collapse. With a lot more sweating and sw#@%@ring I was finally able to fold the bearing onto itself and then to work it out using a chisel.
   The housing was a little worse for the wear but still usable. At one point I did look into whether I could get a new housing if I broke mine and they are still available (for $136)
6. Having gotten the old cutless bearing out, you now need to order a new cutless bearing. The first step is to determine the diameter of your prop shaft because cutless bearings are available in various sizes. My shaft is 7/8" so I ordered the proper size Johnson Duramax cutless bearing ($75).
7. Next install the bearing. First, you need to clean the inside surface of the housing. Rod Collins at Compass Marine has a good description of how to do this with a Dremel tool. But I didn't have a Dremel so I used 320 grit wet/dry sandpaper as he suggests. Even with the cleaning, my bearing would not slip into place. On the advice of my friend, I heated the housing in a 200 degree oven and cooled the bearing down in the freezer. That got it most of the way in so I tapped it home with a hammer and protecting piece of wood. If that hadn't worked, I would have followed Rod Collins' instructions on how to press it into place using a threaded rod and washers.
8. You can now use a hacksaw to cut the bearing to length because the standard bearing length leaves about an inch of the bearing hanging out from the housing. I suppose you could just leave it but I need room to install a zinc on my prop shaft between the housing and my prop.
9. The final step is to drill through the two water inlets creating holes in the cutless bearing so that water can more easily get inside the bearing and cool the prop shaft as well as to travel forward to the stuffing box. Some people say that the holes aren't necessary on a bearing this small but others say it is. I haven't completed this step yet.