Shaft Alignment - CD30, Volvo MD7A

[S/V Ethan Grey]

Reading through the manual, it recommends checking the propeller shaft for alignment once per season. I decided to check mine today because I am leaking around the shaft log and I was wondering if the engine was out of alignment, leading to the shaft log leak. Supposedly, the time to check is with the boat in the water. I’m having her pulled next week so today was my chance to see if misalignment is the root cause of my troubles.

I removed the bolts to separate the two mounting flanges. I then pushed the prop back, disconnecting the two. When I did this, the shaft dropped about 1/2 an inch. That started me wondering if there should be that much play. Should the shaft drop that low?

Am I supposed to lift the shaft up and pull it to the flange, or should the shaft only be pulled towards the flange? I’m assuming that the shaft will sag somewhat and that I should pull the prop shaft up and in to the mounting flange and then check the gap.

Please take a look at the photos and let me know your thoughts. Thanks as always!

[mgphl52]

David, My first thought was have you checked your packing gland? If it hasn't been adjust in a long time that could cause your leak. As for the "drop" in the shaft, I suspect that is due to how much shaft is forward of the cutlass bearing. It could also indicate a worn cutlass bearing?
I'm hoping more astute members will chime in here and help us both!

[Frenchy]

You are surmising correctly that the shaft will normally drop - even with a new cutlass bearing. The bearing is only
rubber and can't be expected to hold the shaft in alignment that far away.
One thing you may want to check before you try to align the engine: the perpendicularity of the
prop flange face to the prop shaft. I had a frustrating time until I realized that face was not perpendicular.
Ideally, the flange would stay on the prop shaft after machining, but it is usually removed and reinstalled to get
it in the boat - unless the engine is removed.
Anyway, to check it, mark the prop flange at 90 degree intervals and put it up to the transmission flange, turning
and measuring at the same point on the transmission flange. You should get the same measurement with your
feeler gauges (or zero gap). If satisfied, check all around as usual for engine alignment.
This procedure takes patience. I found that knocking around the front of the engine to get the flanges parallel
is very difficult without an indication of how far you're moving it. Clamping a dial indicator somewhere near the
front solved that. At least you can see how far you're moving the engine and make adjustments. Harbor Freight sells
inexpensive dial indicators, if you're interested.
Good luck - Jean

[kerrydeare]

... checking the propeller shaft for alignment ... I decided to check mine today ... I removed the bolts to separate the two mounting flanges. I then pushed the prop back, disconnecting the two. When I did this, the shaft dropped about 1/2 an inch ...

I will not contradict others who have responded, but I would still like to offer to my own experiences with the typical CD stuffing box that usually shipped with these boats.

One fundamental problem was that the stuffing box was "hard mounted" to the hull (in fact bolted through the glass) without benefit of any sort of bellows, hose, or possibility of adjustment to address alignment issues. This meant that the system, if not perfectly aligned, would eventually cause excessive wear on the cutlass that was well beyond expected tolerances. After sailing for some while and encountering the typical problems (groundings, picking up a pot or two, etc.), problems could easily ensue.

Many boats provide some sort of "cushion" to avoid this, and I eventually resorted to the PSS system for relief. This was after almost sinking the boat twice due to leaks while sailing "Down island." I well remember swimming under the boat and forcing packing in from below the waterline in order to make it back to a facility to effect repairs.

Rather that force the issue, you may want to consider replacing the original stuffing box with something like the PSS (there are several choices).

[S/V Ethan Grey]

Kerrydeare,

I didn’t realize that the PSS would allow a little more misalignment than the traditional stuffing box. I’ll have to look into this. I wonder if your shaft log/stuffing box installation is different than mine. Maybe Cape Dory did it a couple of different ways. I don’t understand what you mean by “hard mounted to the hull”. For mine, the rear of the stuffing box is visible and accessible. I can see where the rubber tube attaches to the fiberglass shaft log by two clamps. Was yours not like this? What’s weird with mine is that the bulkhead that the shaft log goes through is no longer fiberglass, it is some sort of filler. I don’t know why that is.

[mgphl52]

David,
That is rather strange? Maybe a PO did some "improvements" along the way?
When I bought KAYLA (the first time...) she had a drip-less seal that had been in place for at least 10 years and more likely over 15. When I replaced the cutlass, I had the PSS pulled and installed a bronze packing gland a friend of mine gave me (from his CD25D) since he had just had a drip-less seal installed.
My rational was if the packing gets a little loose much less water is coming in than if the bellows give way.
And the bellows were stated to be replaced at 10 year intervals.

[kerrydeare]

Kerrydeare,

I didn’t realize that the PSS would allow a little more misalignment than the traditional stuffing box ... I don’t understand what you mean by “hard mounted to the hull” ...

I suspect my description itself was less than ideal, and I will try to be more clear and precise. In the old or factory original system, the packing nut is threaded onto the stuffing box which is itself rigidly attached to the hull. This means that the "seal" is not permitted to move at all and fits rigidly to the shaft. Inevitably this will eventually cause wear and damage to the shaft unless the alignment is prefect and rigorously maintained as such. I am referring only to the original Spartan fittings supplied with boats similar to the CD 28.

With the PSS and similar, the equivalent of the packing nut, which is actually a torroidal or donut shape flat-sided part, is instead fitted to a rubber bellows, which is then itself attached to the stuffing box. There is thus a certain degree of freedom allowed in the system, while still maintaining a watertight seal. The design results in essentially no wear on the shaft and allows a certain degree of movement.

Frankly I am not even satisfied with this description, but it's about all I have time for right now. Best bet is to take a look at the PSS literature and diagrams for a better engineering explanation.

[S/V Ethan Grey]

Kerrydeare, thanks for the clarification and the suggestion of PSS. What you’re saying makes sense and is well worth serious consideration. I can’t wait to get the boat hauled to figure out what my real problems are.

[kerrydeare]

Kerrydeare, thanks for the clarification and the suggestion of PSS. What you’re saying makes sense and is well worth serious consideration. I can’t wait to get the boat hauled to figure out what my real problems are.

This is far from a simple issue because we are dealing with gear that can sink the boat. I'm not sure how your particular rig is set up, but in the CD28 the stuffing box is for all intents inaccessible when it comes to maintenance and adjustment, at least for those of us who cannot manager to climb into the lockers upside down, and later get out.

Therefore when we re-powered the boat after about 15 years of heavy use, the first thing to go in after the old engine was removed was a new shaft seal, and at that time (c.1994) the PSS was a hot item. In fact I installed it myself, and I'm far from a mechanic. After that there was never an issue with the seal itself up until the sale of the boat in late 2019. About a year prior in 2018, the cutlass and the Spartan shaft through hull were removed, repaired and a new cutlass installed. That made all the difference in the world in engine alignment, performance, etc., for this very important piece of gear.

Not sure exactly how this info helps you directly, but just thought it would add a bit of background.

[kerrydeare]

You are surmising correctly that the shaft will normally drop - even with a new cutlass bearing. The bearing is only
rubber and can't be expected to hold the shaft in alignment that far away ...

We had a different result with the CD 28. That may be due to the shaft being shorter, but I am not certain.

When we had the old Spartan stuffing box repaired and the cutlass replaced, the shaft was held very rigidly by the cutlass and there was little if any "play" or "drop" or similar issue. It should also be stated that a PSS gland was used and it replaced the original Spartan packing nut, but the PSS actually does not directly support the shaft as it is attached via a rubber bellows..

Based on the above and the result my mechanics achieved with this refurbished system, I would say there should be no "drop" but instead that the engine itself should be aligned to match the shaft, instead of "lifting the shaft" to meet the engine.

Please remember that I am not at all some kind of guru on this, but I did suffer through this aspect of the boat for many decades (and to my knowledge we never sank).

[Frenchy]

Well, I'm no "guru" either, but I've done some reading on the subject and managed to align A Beta 25 and my
old Universal 5424 in a CD 33. About the only way I know of to find the correct vertical transmission flange position is to
let the prop shaft hang down, measure the distance down from the transmission flange and then push the shaft up
as far as it will go and measure that distance. When the the two distances are equal, the transmission output
flange is in the correct vertical position.
Then, it's a matter of aligning that transmission flange to the prop flange so there's less than a .004-.005 gap
all the way around, still retaining the vertical and horizontal positions. It's not easy. Sometimes, in attempting to
adjust the angle of the engine, you throw off the position of the flange.
It seems to me that with a PSS seal and a conventional cutlass bearing, the prop shaft would still be able to
move up and down and sideways. The only guiding being done in that case is with the rubber inside the cutlass
bearing. If you had a stern-tube type stuffing box bolted to the hull, that would definitely restrict movement.
- Jean

[mgphl52]

If you had a stern-tube type stuffing box bolted to the hull, that would definitely restrict movement.
- Jean

On my CD28, it's not "bolted" but glassed in. As previously stated, very limited access for maintenance.

[kerrydeare]

... It seems to me that with a PSS seal and a conventional cutlass bearing, the prop shaft would still be able to
move up and down and sideways. The only guiding being done in that case is with the rubber inside the cutlass
bearing ...

I can only report my individual experience. The new cutlass (of a few years back) was sufficiently supportive (correct word?) that the shaft simply did not move. And I mean that I and others shoved pretty hard. The mechanics then adjusted the engine beds and mounts to match what was (or appeared to be) the "natural position" of the flange based on how the shaft fit and extended from the cutlass.

BTW, this technical mechanical and engine stuff is quickly getting beyond my ken, so I probably have not a heck of a lot more to offer. I predict our local experts will soon chime in with much better answers than mine. That's what we're here for, eh?

Best regards,

Armond

[John Stone]

David
I originally thought I might install a PSS. But I started running across a number of horror stories. Sure, some people seem to love them but plenty of folks have gone back to traditional stuffing box after suffering significant failures. Maybe they weren’t installed correctly.

I have turned away for the PSS dripless and gone with a traditional bronze stuffing box and plan to use goretex or graphite stuffing. Apparently that’s what’s they are using in the USCG...or so I have read. I have also read there is practically no water drips with graphite or gore stuffing. I’ll know more about it after a couple years use.

I have a couple issues with the PSS. The first is its expensive. When maintenance is performed as recommended by the manufacturer it get even more expensive—bellows replacement every six years. Another thing, for me, sailing offshore, if I have a leaky stuffing box I can tighten it. I can wrap the packing nut with waterproof tape. I believe I could stay ahead of any leaks. But if a PSS bellows tears badly it’s going to be a whole lot harder to stop the flow of water. And if I’m hundreds of miles offshore that would be a real problem. You can change flax out with the boat in the water if you had too. If you suffer a bellows tear the boat has to come out of the water and quickly I would think.

Here is an interesting link on things to watch out for. https://waggonerguide.com/dripless-shaf ... ance-free/

Clearly, there are some, maybe even many, sailors that are very happy with them and swear they work great. Over on Sailing Anarchy, a place I normally avoid, there are some interesting threads on the dripless boxes. Folks will say they love them but then go on to say “except for that time when the bellows failed and we nearly sank....”.

But here is the thing, be wary of falling into the trap of treating the symptom. If you have a shaft engine miss-alignment, installing a dripless stuffing box is not going to correct the problem. What you are going to end up with is a worn out shaft log bearing and trouble with the Dripless seal. Any misalignment is going to eventually cause problems. I’d recommend you start with the bearing shaft alignment. Then consider a flexible coupling. Then get a dripless seal if you want.

I recall reading some positive info on the PSS on mainsails site (AKA Marine How To). He seems pretty competent and reasonable. You might find some good info there to help you decide.

I’d also ask Jim W and Steve L for their thoughts. They are both a couple smart experienced sailors.

Happy sailing.

[Frenchy]

I have to agree, John, on the PSS seal. It's expensive, not necessary, and a gremlin waiting to bite you in the
you-know-where. If you forget to "burp" the seal after launching, it can overheat, I'm told. That can destroy the
seal or the bellows. Some have water injection, but again if that system fails, you're in deep trouble. I don't know
how you would replace the bellows without disconnecting the drive flange- another pain- Jean