YACBQ (Yet Another Cutless Bearing Question)

[JetPowers]

I hope not to be redundant - have checked a bunch of prior threads but come up blank so here I go. And feel free to correct any misuse of terminology.
Please see photos:
'79 Fairways Fisher 34 with bearing housing attached by 2 studs to keel. There's just shy of 1/16" shaft play that was not mentioned in survey and upon questioning he says it's insignificant. But shaft chatters on hand spinning the prop and being a motorsailor I expect lots of engine time so I'm considering giving myself some winter work. (Yard owner agrees with surveyor and that it can wait another season or 2, but he's not a mechanic. Then again neither am I and maybe I should leave it be??)
Anyway I'm hoping I can leave the prop shaft, separate the housing and slide it aft right off the shaft. There's room to do so without removing rudder.
Replace bearing on the bench, then rebolt the housing and seal with "xx00" (4200 has been recommended to me). Last 2 pics attempt to show stern tube arrangement from the bilge - seems a watertight seal I hopefully won't be disturbing.
Seems too uncomplicated to be true. Any pitfalls/advice? Might attempting to loosen the studs and separating the housing prove a regretful action? Thanks.

[capt jgw]

You won't know until you try. I can't tell from the pic of the bearing housing is just booked on the outside or does it go all the in. It might slide right out, or it may be stuck in there with 5200. There has to be some kind of sealant between it and the hull or it would leak. If it won't come out you'll have to pull the shaft. There are a few options after that, cut the bearing apart with hack saw blades, pull it out with a puller, etc. Strut mounted bearings are easier, there is a puller that works with the shaft in place. The hardest part of pulling the shaft can be getting the coupler off. Sometimes they come off easy, other times they fight you.
Once when I had to replace a shaft I actually pulled the engine out and pulled the shaft out and back in through the cabin. I would have had to drop the rudder to go the other way and there wasn't room under the boat for that, and on a paved parking lot so I couldn't dig a hole.

[crosswire]

Two possibilities:

One - The inside photos appear to show a grease lubricated stuffing box being used as an intermediate bearing as the shaft is visible on both sides of this stuffing box. I would have expected to see another stuffing box further aft, which is normally through bolted to the cutless bearing housing outside, which would provide the actual seal between outside and inside the boat. If this indeed the case, I would leave the cutless bearing alone as access further aft looks very tight.

Two - The photos may show the shaft enclosed in a tube that connects the outside cutless bearing housing to the inside stuffing box. If this is the case, I would leave well enough alone until the method used to seal the tube at each of its ends is known. It could be screwed or soldered to the cutless bearing housing.

The chattering mentioned may be the result of the cutless bearing being dry. Did the shaft chatter before the boat was hauled, when the engine was in use?

If the cutless bearing housing is removed, remember there may be one or more allen head screws hidden under paint that need to be loosened before the bearing can be removed.

If the existing cutless bearing is not replaced, be sure to keep the water flush ports on the cutless bearing housing open so the bearing gets lubricated.

[capt jgw]

Pretty much what I was thinking. If the part on the outside is just bolted to the shaft log it should come right off and changing the bearing will be easy. With luck the visible bolt heads on the outside are lag screws and they'll come out easily. If they're through bolted to something inside that could be a problem if you can't get to the nuts. If it's part of the tube inside it's not coming off and you'd have to change the bearing the hard way. That job can wait till it absolutely has to be done.

[capt jgw]

Actually if I were doing this job I'd start by seeing if the shaft coupler will come off easily. No matter how the bearing housing is put together or will be easier with the shaft out of the boat. You then get a chance to check it for straightness, corrosion etc. If the coupler comes off too easily it should be replaced, that should be checked periodically.

[JetPowers]

So all my concerns have basis then. Yes there is no aft gland and seeing no hardware haven't a clue the nature of the joinery. That stern tube HAS to be embedded but can't tell if it's joined to the outer housing.
I do want to soak the bearing but water was shut within 3 weeks of my arrival during which I was occupied learning to winterize. As I've many distractions once March rolls around, the biggest being inspecting and maybe changing 40+yo rigging on 2 unstepped masts, I can't deal with dropping a huge slab of rudder and decoupling the shaft under the gun. I'm too green to do these projects quickly and I might never get on water.
So I might just leave it go the season. It's within tolerance right now. I do not trust my surveyor (SAMS no less) but maybe I will have to.
Worst scenario if noisy with vibration is boat gets hauled early. Maybe better than not attempting to have a season.

Have a couple thoughts though before defeat - see if the present sealant has any give and if so cautiously untorque the studs. My biggest fear is being caught in twilight zone half off and unable to re-seal properly. Then I've bought the big job.
Also maybe join the UK Fisher group and post there. I'm sure it's a common set-up.
Thanks everyone for responding.

[capt jgw]

That may be the best course. You don't know the state of the studs inside the fiberglass and if they are to corrode badly that's where it will happen. Worse case is you start to turn a bolt and it breaks off. Been there done that.
Of course someone who's done the job on that model boat is your best reference, we're just guessing.

[kenbo]

I wouldn't be too quick to assume the cutless is the source of the chatter. How old are the motor mounts? If they are old/original, the motor could have dropped a bit and the shaft could be hitting the shaft tube.

I'd pull the shaft packing off the tube and see if the shaft is centered. If you have a dial indicator you could check the shaft for runout as well.

[JetPowers]

Originally Posted by kenbo

.....the motor could have dropped a bit and the shaft could be hitting the shaft tube.

I'd pull the shaft packing off the tube and see if the shaft is centered. If you have a dial indicator you could check the shaft for runout as well.

Thank you. Good advice. Amateur machinist, I'll try the dial indicator

[skipperpete]

First, the chatter, you need to slide the propshaft back far enough to view the area on the shaft that contacts the bearing and see how that looks. It should be shiny but could also have a calcium buildup where the shaft has a gap between itself and the bearing, its like a crust of 120 grit sandpaper and is easy to remove. The less pleasant cause of the chatter could be corrosion that occurs along the area where the bearing flutes contact the shaft, usually a straight line of pitting in 3 or 4 places.
There’s a fair chance that the bearing carrier in your photo is threaded onto the stern tube and those bolts are only there to stop it rotating..... no biggy, but beware of undoing the stern tube where it threads into the stern gland carrier as you turn the bearing carrier to get it off the stern tube.

[Toccata]

I'll save you a lot of research and reading, with a summary here, but do read Gerr or Calder on this issue so you are familiar with what you are taking on BEFORE you start.
You probably have an inner bearing behind (aft of) the stuffing box. The exposed metal aft of the inner bulkhead looks like the outer surface of the stern tube. The outer bearing carrier should be screwed onto the aft end of that tube (The inner bearing likewise is screwed onto the stern tube which is threaded thick wall bronze or similar.)
If you remove the outer bearing carrier, the replacement cutlass bearing should go back into the old housing and be centred/aligned with the shaft, but, if the carrier/housing doesn't fit back exactly where it came from or the shaft has worn the original bearing into a new centre, you have created (or revealed) an alignment issue. Chances are the carrier/housing will go back into the same place as it will be threaded/screwed onto the stern tube.
To do this properly IMHO
Steps: Remove the shaft to check it. Remove the cutlass bearing. Reinstall the shaft, fit the inner coupling and connect to the engine.
(You could possibly leave the shaft in place, remove the prop, unscrew the bearing carrier and slide it off the shaft. Note support the shaft or you will see that it is drooping and so stressing the inner bearing.)
Slide the replacement cutlass bearing along the shaft looking for a precise fit into the outer housing. Happy days!
If the replacement cutlass bearing won't go into the housing: Disconnect the coupling (from the engine) and see if you can then slide the new cutlass bearing into place after the shaft finds its happy place in the inner bearing and you then know you have an alignment problem, which should be solvable by adjusting the engine mounts. OR
Machine the new cutlass bearing outer diameter down "a bit" (in small steps) until it slides into place, epoxy it into the housing (bearing carrier) and refasten the grub screws. In this case he shaft is the alignment tool. In the second scenario you are accepting the current engine/shaft alignment and fitting the cutlass to that. This may be problematic as the engine mounts maybe old and flogged out, the engine could have settled, the previous owner may have played with it and got it wrong.
If you have a raft of other stuff to deal with the outer cutlass bearing may be a lower priority. Steps: I would check the engine alignment when next in the water (it will be different out of the water due to different stresses on the hull) and see what that does to the vibration.
Check the condition of the soft engine mounts, if old and squishy, replace them.
Consider fitting a flexible device between the engine/gearbox flange and the prop shaft. Note this will push the prop aft by an equivalent amount and require either moving the engine forward or shortening the prop shaft to reestablish the correct amount of unsupported shaft aft of the original bearing housing. But it would be considered good practise to have some sort of flexibility between shaft and engine if you also have soft engine mounts. Also in your case I suspect you have an inner bearing/bush in which case the flexible coupling is even more important given the shaft is supported right at the inner gland.
Then there is the question of what type of material to use for the new bearing. Locals here favour the "rag type" others will swear by the rubber type.
Thread Drift.
I also cannot see any anodic protection of your prop or shaft. You may consider adding a shaft anode between the prop and outer bearing carrier, or an anode with strap to the outer carrier although this will be insulated from the shaft and prop by the cutlass bearing. OR an inner shaft strap type contact bonded to an anode. You may accept it as is because your prop appears ok depends if you are going to other marinas with possibly dodgy electrical issue......complicated isn't it!
I think I have covered the basics, others may chip in and complete the story if I have missed anything. Goodluck.

[Toccata]

my mistake. You do have a short length of rubber hose between the packing gland and the inner end of the stern tube.
There may be no inner bearing at all, just a free floating shaft with the packing gland in the floating section, or the bearing/bush may be in the casting holding there inner end of the stern tube.
If the inner bearing is in the floating section it is not really performing as a bearing but just a guide to keep the packing centralised on the shaft.
This all makes the alignment issue a bit different.
The inner end of the shaft maybe relying on the engine for support, so disconnecting it will allow the shaft to settle on the side of the stern tube.
Several things to consider here:
Check the condition of the engine mounts. Decided if they are reusable.
Split the coupling and do an alignment check. Just to see if it's "in the ball park" (Note if there is no inner bearing the shaft will drop down when released. I would make a support or tie it up to something, before disconnecting it just in case there is no inner bearing)
Disconnect the rubber hose and pull it off the stern tube (slide it forward) to see if the shaft is sitting roughly in the centre of the tube at the inner end or indeed if there is a bearing there. This will give you a rough idea of existing shaft alignment.
Slide the prop shaft back and look for wear on the outer end of the shaft.
Attend to the outer cutlass bearing, either by removing the whole outer assembly leaving the shaft in place or slide the shaft out and replace the bearing with the housing in situ (rudder removal probably required)
It's all relatively simple, low speed, low tech engineering, but there is a degree of interpretation required at each step as to how tight something is, how much movement is acceptable, how much wear is acceptable, ideally a marine engineer would cast their eye over your assembly.