Coupling and Shaft Alignment

Newsgroups Archive Prior to 2025
1

Just had my engine mounts replaced, it’s a relatively new engine but the engine mounts must have been re-used as they were badly worn, one was also corroded. The replacement went well, but the mechanic noted that the half coupling at the end of the shaft was loose, and has likely been enlarged. Therefore a new half coupling is required at some point soon. Of more concern is the PSS shaft seal bellows, which is starting to show signs of being worn out.

All of this unfortunately means haul out shortly in the New Year, something I was hoping to avoid in a season that was supposed to be about sailing, not maintenance. I’ll have to re-build the shaft seal and sort the coupling. While I’m at it I’ll replace all of the through hull valves with some of those new graphite units that turn so easily. I’m also going to eliminate the raw water through hull aft of the galley sink, which I do not use (I’ve dedicated the forward tank for the head).

Such is the reality of owning what is nearly a 30 year old boat…reflecting back I think that most of the boat is now new.

John
NS30U#400
New Zealand

2

2 questions:

  1. The shaft tube is 1 3/4"?

  2. Also, does anyone know what thread and size the through-hull fittings (factory) are?

John
NS30U#400
New Zealand

3

Confess, John - all of us know that you dig the maintenance. It shows in your (beautifully kept) boat.

It might snow here, any day now …

Ernie A. in Toronto

4

Maybe the engine mounts and misalignment with the shaft caused the excessive vibrations in the cockpit. If you have space consider installing a Aquadrive or similar universal drive between the motor and shaft. With to thrust bearing glassed to the hull you can use softer mounts and not having to worry about alignment as long you are within the limits allowed which is a few degrees. As for the stern tube, you better measure it. I have seen differences between NS 26 hulls. Just follow the PSS instructions exactly. If the shaft has been misaligned for some time check the strut, shaft bearing and that the shaft is straight.

Good luck,

Jorgen Moller

PONDUS NS26 #33
Toronto

5

That’s one of the reasons I don’t like shaft seals and prefer old fashioned packing glands. Don’t have to haul to replace the packing. Hopefully the end of your shaft is still within tolerance.

Joe Valinoti
S/V IL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

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6

I suppose I won’t know if the shaft has been worn or just the half coupling until I take it all apart. It’s currently tight, but when the set screws are backed off there is play. Not ideal.

I think the bad engine mounts definitely contributed to the vibration, I’m keen to see if there has been an improvement, but of course the sound proofing will also affect this now.

I do enjoy the maintenance, but I dislike hauling out, as it is quite expensive, and I stress that the clock is ticking and tend to work round the clock while it’s in dry dock.

John
NS30U#400
New Zealand

7

All,

Having replaced a shaft seal a couple of years ago, I can recommend the following be performed as “Shaft Maintenance”:

Replace:
-traditional stuffing box with PSS shaft seal or similar. Properly installed will give you years of service.
-Coupling - Solid is better than split, check for flatness of plate to shaft - lathe with dial indicator, +/-0.001" acceptable.
-Shaft - have one made as a loose coupling will have damaged the shaft
-New coupling bolts - of course :slight_smile:
-ensure keys are tight fit, both ends.
-engine mounts - inspect and replace as necessary
-engine alignment, 0.001" feeler gauge must not get stuck between coupling and transmission plate anywhere.
-check/verify transmission function while down there, should be quite and smooth no clunking.
-cutlass bearing - replace

The above will run you around $1000 plus your time.

Joe

8

Oh, and one more thing. Make sure your log (shaft) is centered in your stern tube! Very important to a good alignment job. Misalignment will cause uneven wear in your dripless or stuffing box.

9

I had a local yard replace the packing about 5 years ago and it still is not leaking. The cost was about $50.00 total.

Joe Valinoti
S/V IL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

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10

And if you reuse your traditional stuffing box, replace with proper stuffing, not the garbage teflon crud they used 10-15 years ago. That stuff ate shafts around here, wore nice grooves in them. Have a couple of wrenches made to maintain your stuffing box if you don’t already have them aboard.

11

I have used Teflon and don’t remember a problem except that it did drip. The last was done with graphite and it doesn’t. I was surprised and checked the temp of the packing area with an infrared and it was fine.

Joe Valinoti
S/V IL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

~ ~ ~ ~ ~ (_ ~ (_ ~ (_~ ~ ~ ~ ~ ~ ~ ~ (_ ~ (_ ~ (_~ ~ ~ ~ ~

12

I use a Teflon packing and it drips so infrequently as to be none existent.

13

I guess two school of thought. Stuffing box - traditional, Shaft Seal - Modern. Both have inherent advantages and disadvantages. Since moving to the PSS, I have no drips, no unscrewing of the stuffing box while in reverse and no worry. As I am motor sailing most of the time, it gives me confidence that everything is going to be fine downstairs.

Teflon as many know, is a wonderful material invented and manufactured by Dupont. It has a high melting point, chemical resistance, wear resistance and excellent electrical insulation properties. However, it is totally inappropriate for use as a shaft seal. Due to those properties listed above, it will gaul the shaft if it is allowed to over heat due issues with the drive - witnessed around here on a few shafts. Issue could stem from a variety of causes, such as: shaft misalignment, overload, worn cutlass and or other components, over stuffed or over tightened stuffing box. Traditional stuffing works fine as the stuffing material will fail at a much lower temperature in a way acting as a failsafe to indicate issues that need addressing. They should and will drip or seep accordingly. To some, this is not acceptable. That is purely a personal decision as a traditional stuffing is tried and trusted.

For me, when I got a new prop a couple of years ago, it was time to address the shaft and box that was leaking and unscrewing all the time from vibration. That is a great time to upgrade!

Issues with PSS? No issues at all as long as your mounts and alignment are good. I burp mine every time the boat is launched so that the air is let out of the stern tube and allow the lake water to act as the heat sink. The mating surface (seal) of a PSS is much higher than that of stuffing box and truly drip and worry free.

My advice if you are hauling out, have all the replacement parts ready, cutlass, shaft, coupling, bolts and (PSS or new stuffing and hose). That way you are not wasting time. Time = money! Oh, alignment can take 1/2hr or 6 hours. It all depends on a bit of luck. Mine took about 2 hrs in -15 degree Celius in March!

By the way, this was all “learned” to me by a good friend and retired shipwright who is the only person I allow to touch my boat now.

Oh, if you don’t have access to a machine shop, a pair of narrow wedges on your solid coupling will be your friend :slight_smile:

Regards,

Joe

14

I have been lead to believe that the issue with “drip-less” is somewhat like the term stainless. Operative word is “less” not “none”. If there is no exchange of water in the shaft area then crevice corrosion will occur on the shaft. As well if it is sealed tight boat motion or prop action can empty the tube and then you have no water cooling at all. Being sealed and with the the upward shaft angle it will not refill easily as there is no where for the air to be displaced. The PSS units now all have a vent for this reason.

I use teflon shaft cord as the lubrication is a good thing , but I do have a drip, as I feel drip less is a bad thing… and a diaper in place the catch the water that I can remove every so often.

15

I’m likely going to simply rebuild (new bellows and grub screws and o-rings) or replace the PSS shaft seal that I have now. It has been absolutely maintenance-free to date (some 8 years). I won’t really know the condition of the shaft until I pull it all apart, but I’m hoping that the relatively short 1" shaft won’t run into multiple hundreds of dollars if required.

I’m certain that the bad mount contributed to the vibration, but by the time I get everything fixed I’ll have completed the soundproofing exercise, so the resulting improvement will be a combination of measures.

Of interest to some, I’ve decide that the best way to run wires and hoses around the engine room (where I don’t have a plywood panel) is to epoxy small plywood blocks to the fibreglass (underside of the cockpit), then glue the foam soundproofing over top. Screws can then be driven into these blocks rather than the fibreglass itself. I can’t think of an easier method. There are just a few cables and hoses that must transition along the bottom of the cockpit, there is no better route.

John
NS30U#400
New Zealand

16

John,
With regards to your plan for the wiring you may want to think of future access. If you put the sound insulation panels on first and then attached the wires to it you may not be able to access them without removing the sound insulation. The panels I used have a hard outer surface that hold screws without any problem. If that is not an option consider running some cheap conduit or hose that you can run the wires through and just remove the foam backing from the insulation where it goes over the conduit. This might be less work then then installing wooden stringers.

Mark Powers
La Reina 26c
Vancover, British Columbia.

17

Regarding the coupling, I thought old one was too loose as well and this might cause some shaft vibration but a new one fit on the shaft just as “loose”. Maybe it was the shaft that was worn but I don’t think so.
Pulling shaft, repacking stuffing box, replacing cutlass bearing all ok and relatively quick but the coupling took much effort to get off the shaft. This has been discussed before. The setscrews raise a couple little bumps on the shaft which prevents the coupling from just sliding off even though it’s still loose just after you back off the setscrews. You have to force it off by placing a nut or an appropriate socket between the transmission and the shaft then tightening a couple of the bolts back up, repeat with a longer socket until the coupling comes off. Later a couple passes with a file takes the bumps off so the coupling goes back on easily.

Also getting the old cutlass bearing out was relatively quick but I didn’t know there were two set screws holding it in. These were covered and filled with paint. On my 26 they are on the port side of the strut. If you take some sand paper and clean off this side you will see them. The Cutlass bearing is an interference fit in the strut so you have to destroy the old one to get it out by cutting it with a hacksaw but it might come out much easier if you remove these set screws first You may have to drill them out.
Have something like a 5/8" threaded rod that is about 2.5 times the length of the cutlass bearing, 2 nuts, and two heavy washers ready. Use it to squeeze the new one back in. An easy job really.

18

I have the W13 in my 26 and have been trying to get the vibrations down for 9 years now. Did everything the list suggested. New mounts, clean fuel, coupling, check straight shaft. Last year I replaced the martec prop with a fixed plastic prop. The martec had worn pins. This made some difference, maybe 10 %?
The W13 is just a noisy, vibrating beast so it can’t be helped.
My solution is just to turn it off as soon as possible.

Tom
NS26 # 28 North Star
Penetang

19

One of the things we did when putting the new solid coupling on the new shaft is dimpling the set screw position PRIOR to installing the coupling permanently. What we did is the following:

  1. Slide the coupling on the shaft with key inserted. You may use a piece of 4x4 on end grain and use gravity to tap the coupling on by banging like a tamper. Crude but safe.
  2. put a drill in the set screw hole to mark the location of the two (2) set screws (90 degrees apart - in my case). Drill size should be the ID of the set screw thread (minor diameter).
  3. remove coupling
  4. put the shaft into a vise on a milling machine or drill press and plung with round nose/ball cutter, perhaps 1/4 dia (or match the diameter of the set screw), - 0.050"-0.125" deep
  5. Modify set screw on grinder to form a round end to the same diameter of the plunged area.
  6. Reassemble coupling with key and insert set screw with locktite blue.

Now, this may seem excessive, but, I can crawl on my hands and knees if I have to, in the open water, and get my coupling off. I have no worry of the setscrew galling the shaft which makes it impossible to remove the coupling without destroying the shaft. Never mind what happens after the coupling gets loose and starts to mince the shaft. My coupling was oval by 0.050" by the time I took it off!

Ounce of prevention, worth the pound of…

Do it once, do it best!

Joe

20

Lastly, we used:

https://www.deepblueyachtsupply.com/

Was around $375 USD shipping to Buffalo NY (we live an hour away in Canada) for new 1" shaft and solid coupling.

1/2 the price from something similar in Canada.

Joe