Should I face the split coupling?

[LordGothington]

I have two questions.

I am replacing pretty much everything astern of the transmission coupling -- a new shaft coupling, a new prop shaft, a new stuffing box (the hose, the bronze parts, and the hose clamps), a new cutlass bearing, and a new propeller.

Q1) I am using the split coupling -- there is no pointing in getting a 'fitting' done since it slides on with little force. But should I still get it faced? Or is facing pointless because things will shift a bit when I tighten everything anyway? I asked Don and he said 'no', but also said to ask in the forums.

I can not pre-install the coupling -- I have to install the prop shaft from outside the boat, and then put the coupling on.

I am going to invest in a dial/needle gauge setup for checking the engine alignment later -- perhaps there is some way I can use that setup to see if I need a facing or not?

Q2) With everything being brand new, there is quite a bit of friction between the shaft and the cutlass and also the shaft and the stuffing box -- specifically the bronze section of the stuffing box. Should I be concerned? Or is that normal? Perhaps after a short break-in period everything will turn more freely? I can turn the prop shaft by hand -- but it is definitely not as easy as the old system. On the other hand, I replaced the old system because it was worn out.

I expect that in a battle of the AQ-22 stainless steel prop shaft and the bronze coupling, the prop shaft should wear down the bronze pretty quickly -- allowing the shaft to turn more freely. (side note: I have not installed the flax packing yet, so the friction is definitely not from the nut being too tight.)

In summary, is there anything worth doing before I install this coupling? I searched the forum and saw 1 vote for not needing to face the split coupling and 0 votes for facing it.

Thanks!

[lat 64]

I have been under the understanding that a .005" feeler gauge is all that is needed to get the shaft alignment.

Seems to me the vagaries of a fiberglas hull sitting in the morning sun would warp* and change the shaft alignment more, and make the accuracy of a dial gauge moot.

*I've seen it happen on commercial fishing boats.

[ndutton]

Lord, a dry cutlass will impart a significant torque load on the shaft, especially a new cutlass. Also, the contact between the gland body and the shaft should disappear after the packing flax is installed because it centers the shaft within the bronze casting.

You can eliminate most of the dry cutlass load by applying some liquid dish soap, it's a good trick when installing the shaft too.

[Al Schober]

If you're concerned about the face of the coupling, it's easy to put the coupling onto the shaft and lay the shaft in some wooden V-blocks on your workbench. You can rotate it by hand and check the runout with a dial indicator.
Shaft should turn freely in it's bearings. As suggested, some dishwashing soap on the rubber cutless is good. Similarly, I'd run a piece of emery paper inside the stuffing box - a small burr could be dragging.
Final alignment should be done in the water. I've seen BIG changes in alignment due to the sun heating one side of a hull.

[sastanley]

All good suggestions above...I would also recommend springing for the gore-tex packing..you can almost get it to a dripless state, after a couple of adjustments. Spring a few bucks for a spanner wrench out of the plumbing dept at the hardware store..that is easier than two channel locks..I started mine pretty loose to make sure I was getting adequate cooling, and slowly tightened it up and made sure I could still keep the stuffing box cool enough to wrap my hand around it and hold on to it.

Also, +1 what Russ said on the feeler gauge. You simply mate the coupling to the engine and then use a feeler gauge and get the distance equal all the way around, down to 0.005". A little trick someone (Neil!) explained to me long ago was the back engine mounts are 'gross tune', and the front mounts are 'fine tune', when aligning the shaft.

If you have Nigel Calder's Boatowner's Mechanical and Electrical Manual, it has a good explanation as well.

[LordGothington]

Thanks everyone!

I totally agree that there is no point in checking the engine alignment until the boat is back in the water.

The concern is that if the face of the coupling is not perpendicular to the prop shaft, then there is no amount of engine alignment which can eliminate prop shaft wobble. Consider the extreme case where the prop shaft is coming out of the coupling at a 45° angle -- there is no way you could align the engine that would get the shaft to spin straight.

On the other hand, facing only makes sense if the alignment of the shaft and face in the coupling is repeatable. If I get the coupling faced, take off the coupling, and put it back on and it is aligned slightly differently, then I would have lost the benefit of the facing -- but would be $80 poorer and probably 2 more weeks behind schedule since the metal shop probably has a waitlist. (And yes, I know cruisers aren't supposed to have schedules).

I considered gore-tex / GFO / GTU packing, but decided not to take the risk. It is impregnated with graphite, which is the most noble element in the galvanic series. I have repacked my stuffing box in the water, in general I haul the boat once a year anyway, and I am not concerned about eliminating a few drips per minute. For other reasons, I can't effectively keep a dry bilge.

I know many people use those packing materials and their prop shafts haven't fallen off yet. Additionally, my shaft is AQ-22. I am willing to be convinced, but at the moment I see risk with no real advantage to me. Here is one example of an extreme case that was blamed on the graphite based packing material:

https://forums.sailboatowners.com/threads/stuffing-box-packing.159570/post-1090387

Having used a variety of ill-fitting wrenches in a cramped space to adjust my stuffing box in the past, I treated myself and got a set of these,

https://www.catalinadirect.com/shop-by-boat/catalina-28/engine/maintenance/stuffing-box-wrench-set-1-78quot/

I have not used them yet, but I think they are going to make life way better.

I've used feeler gauges in the past to check the alignment, but was not that satisfied with the results. The gauges seemed to indicate everything was in alignment, but I still got a lot of stuffing box wobble. However -- it turned out my cutlass needed to be replaced -- so no amount of alignment could fix that.

I am going to cross my fingers and hope everything is in alignment when I relaunch. My engine is not on nice adjustable engine mounts -- it is bolted onto some angle iron that is fiberglassed into the hull. To adjust the alignment it appears that I have to loosen some bolts and manually insert thin pieces of metal.

This is not the best photo, but if you look in front of the flame arrester, you'll see a stainless steel bolt, and underneath the engine there are some brass/bronze shims:

https://photos.app.goo.gl/9BvZY36G5NjfF8dRA

I'll try the feeler gauges again -- and if those aren't giving me a useful answer I may try this method,

https://www.youtube.com/watch?v=CLyG-8wq268

As you may have gathered from this thread, my experience in attempting to address stuffing box wobble/shaft alignment is limited to a single case where at least one of the culprits was a worn cutlass bearing. Since I have never been in the situation where everything was 'working' I don't know what that feels like

[ndutton]

Please don't ask where I got this . . . . . .

The idea that a split hub coupling should be refaced after installation is due to the perceived notion that they go on more loosely than the standard non-split couplings and will therefore be off-center after tightening the retaining bolts. In reality, our split hub couplings have the same ID as our non-split couplings so there is no need to face the split hub couplings. The benefit of the split hub design is that it is much easier to remove them years down the road, not that they will go on easier.

[LordGothington]

Please don't ask where I got this . . . . . .

Alas, this just adds to the confusion! It would seem to imply that people only want to face split couplings but not solid couplers. But it is my understanding that with a standard solid coupling, the standard practice is to fit & face.

So in the case of the split coupling what exactly does 'reface' and 'after installation' refer to?

Was the coupling already 'faced' before I bought it, so I do not need to 'reface' it at all? Or maybe I am supposed to face it to match my prop shaft, but I do not need to 'reface' it after the coupler is removed and reinstalled?

So far I am leaning towards doing nothing and just installing the darn thing. Worst case -- I have to remove the prop shaft and coupling while the boat is in the water -- which can be done

And now for something completely different.. it seems that the split coupling is 0.20" thinner than the old coupling, so the original bolts hit the transmission case before I can tighten them all the way

So I am going to order some 3/8"-24x1" bolts instead. But.. should I get Grade 8 or 316 Stainless Steel?

My inclination is the 316 SS, because.. why not?

[ndutton]

Lord et al, I apologize for what I'm about to do but it's time to waive my resume' around a little.

I built sailboats throughout most of the 1970's and among other things, installed literally hundreds of engines and drivelines, the most common being, you guessed it, the Atomic 4. Not a single driveline went through any fit and face shi-shi at any of the manufacturers I worked for. The couplers came on the engines, the shafts came from a different vendor. They were taken off the shelf and installed in the boats with maybe a little hand dressing with a file by the installer (the common shaft material at the time was bronze so hand dressing was viable). The points where the coupler set screws landed on the shafts were dimpled on a drill press before final installation and that was about it. There was no lathe or mill work done to either the couplers or the shafts, never.

I also worked in customer service at Islander Yachts and never dealt with any issues with drivelines installed this way. For more in depth reading on factory installed drivelines click this link:

http://www.moyermarineforum.com/forums/showthread.php?t=6530

Please consider that we are not building a jet engine here. Our RPMs are very low and our hulls flex so really all this fussing over precision machining is overkill in practical terms. It reminds me of something I learned in college chemistry labs, significant figures. We could not report a quantitative result out to 4 decimals if our measurements were made in single decimals.

FYI, the quoted text in my previous post came directly from Don Moyer. You'll be hard pressed to find better information anywhere.

[LordGothington]

Lord et al, I apologize for what I'm about to do but it's time to waive my resume' around a little.

Thanks! As noted above, I know just enough to be dangerous. I can see how things *could* be a problem, but I lack the experience to know *if* they are really a problem.

I've decided to install the coupling as-is. Either it will work and I will save time and money, or it won't and I'll learn something. But it seems likely that it will work just fine.

I can see how the facing could be important for a higher RPM engine and a longer prop shaft. But on an Atomic 4 with a 36" prop shaft, I can see how the manufacturing tolerances could be good enough to work out of the box.

[ndutton]

I can see how the facing could be important for a higher RPM engine and a longer prop shaft. But on an Atomic 4 with a 36" prop shaft, I can see how the manufacturing tolerances could be good enough to work out of the box.

Absolutely!

Even though it was not the question you asked, as long as I'm on a roll I'd like to offer a comment on the 'fit' aspect of the 'fit and face' coupler/shaft pairing. Think about what happens to a marine transmission when a coupler/shaft fit is made so tight that it must be installed with a sledge hammer.