Replacement Flex Coupling

[delmarrey]

Oh yeah! Here's another source I forgot to mention for soft couplers.

R and D MARINE : Flexible Shaft Couplings

[Psyches]

Here's a picture of my problem (sounds like the same as clausont has/had); the rubber is still in really good shape, but you can see how it's disconnected at the bottom end where the propeller shaft is. It also looks like maybe there were bolts or pinds into the rubber that sheared off, kind of hard to tell for sure:

[delmarrey]

I don't know where one would get a vulcanized prop shaft coupler but as a Machinist who has built dies for vulcanizing I can tell you that the one in the picture is really a bad design. And vulcanizing is not used in a high stress twisting application w/o special reinforcements. A Rubber to Metal Bonding Informational Page, About Rubber to Metal Bonding.

And, as well, it looks to be way out of alignment (if both parts are still in place). To add SS lock washers and/or bolts are not recommended on moving parts. They expand and contract with temperature change and movement and usually come loose. AND, lock washers are not used under nylock nuts. A grade 5 or 8 (then painted) would be better. They can be torqued to spec's and will stay that way.

Now that I've picked your picture apart I'd recommend go to this type of set up (after you get the alignment squared away).

[Psyches]

delmarrey,

Thanks for the info; I've only been a boat owner for 6 weeks, but as far as I can tell the rubber piece is the original design for the Tartan 30 series and some others from 30 years ago. I don't know whether the nuts and lock washers are new or what.

It looks like others have asked questions about these parts too - here's the part on someone elses boat:

http://i18.photobucket.com/albums/b1...b-Coupling.jpg

My engine is a Farymann A30M 1-cyl, about 10hp. It shakes like crazy, as mentioned earlier in this thread. If I went with the setup you showed, would you not be concerned about the vibration? Also it looks like the coupling you show is shorter than mine - how might I address the gap?

re: alignment, I've pulled the shaft around a bit to see how secure it is, rotated it some, and probably misaligned it. But on my boat, the stuffing box is connected to the rubber packing gland hose, which I think is also the original design. Then the shaft goes through to the cutlass bearing (which I understand is new on my boat) and rubber packing gland in the "middle". So there is rubber pretty much all around here.

I'm ignorant about most of this, and anxious to both learn and get my boat fixed quickly.

[delmarrey]

It seems obvious that the old style has had a lot of failures (three so far just in this thread). Here are some other options but not cheap I'm sure. I'd be willing to say that you'll have a hard time finding one of the old vulcanized styles.

Engine shaft vibration blocker coupling - EFSC - THE-EVOLUTION-COMPANY-INC - NauticExpo

CENTA Power Transmission - USA - Products - - CENTAFLEX-A

Stromag USA: Products: Couplings

This one on the left would require a support bracket for the prop shaft.
Engine shaft coupling - PROFISEAL - NauticExpo

As for the gap/spacing, anytime one is retrofitting from an original design, one may have to make changes. As in a longer/shorter prop shaft & different flanges.

[clausont]

Psyches- I did finally find a direct replacement coupler for this boat.It was even mentioned by one member here on the forum but I didn't look close enough at what he told me.
PRP Inc. - Global Engine & Engine Parts Distributor - Welcome to PRP Inc.
Call these guys here - they have the couplers coming in (i talked to them just this morning) within a few days. The four bolt coupler is $300 + shipping and the three bolt is considerably less.
They do not show the four bolt on their website - only the three bolt. Changing the coupler should be pretty straight forward. Mine is out and ready for the replacement to drop in.
Make sure to call them soon as they go out of stock FAST and have to be imported from Germany.
Thanks all here who helped on this.

I should mention that this is an excellent time to repack or inspect the stuffing box also.

[clausont]

Delmarrey and Psyches - The next time I haul my boat, I will likely replace the shaft and coupler both (and flanges of course). I will probably be replacing the coupler with an R&D.
My concern is this: The Farymann shakes ALOT and I am concerned the there may not be as much give laterally in the R&D as there is in the vulcanized coupling at 3" long to absorb the shake of the engine. All of my mounts are good. Any thoughts on this
? My shaft is not long enough right now to add the R&D or O would probably have done it that way.
I checked with a rubber mill in Portland, OR who thought they might be able to revulcanize the coupler, but after looking at it, they said it could not reliably be done.

[Psyches]

I did call PRP and get the part number for the 4-bolt, $300 coupler: it's prp-0075. I've learned a bit more too:

(a) turns out my coupler was <6 months old, that's why the rubber looks so new...it is new.
(b) the rep from PRP says he's never heard of a part immediately going bad - there are two failure modes: if the rubber tears, that means the shaft was held (wrapped up, ...), and if the metal separates/becomes unbonded, that means "shaft misalignment"

So it looks like as some noticed/suspected here, I have an alignment issue. I'm not sure what to do about that yet.

Longer term, I agree with others here, it looks like moving to a different coupling system sounds like a good thing. Hopefully I can make this one (another new one, I guess) last at least another year.

[Psyches]

Sorry to prolong this, I'm still searching for near-term solutions and have a (probably dumb) idea. I'm planning to buy another coupling, then the broken one will be a spare if I can fix it.

The broken one is new - why shouldn't a good metal-rubber adhesive work to connect the metal plate back to the rubber? Say something like Marine Adhesive/Sealant #HM11301.

Does this stand a chance of working? Max rpms on the engine is <2900, Hurth 2:1 reduction makes it <1450 rpm on the shaft or 24/sec. Seems to me that a good adhesive might work...

[DeepFrz]

Psyches, could you get someone to make adapter plates for you that would fill the gap and allow you to use one of the better flex couplers? I would hate to take a chance with a rubber adhesive and have it fail in a seaway.

[Psyches]

Yes, I've thought about having an adapter made - ideally I'd be able to use the current setup for awhile, but we'll see. I have some new information though: the rubber isn't bonded at all. I took it apart last night and found there are bolts going thru the rubber from the metal plates on both ends. Looks like ~1.5" x 0.125" bolts on both sides, but I haven't taken one out. All 4 bolts were sheared on the prop shaft (aft) end. I think I could get the stubs out and replace the bolts.

Also, I found that the prop shaft doesn't turn easily at all, as it was or when pulled back into position. I can force it to turn using both hands, but it's hard. So I'm thinking that's the the original problem and cause of sheared bolts. Still don't know if the prop is fouled or what yet. I guess it'd have to be either that the prop is fouled, or the cutlass bearing or stuffing box is frozen, right?

Another strange thing is the aft bolts didn't seem to be holding anything together (see the picture in this thread) . The forward bolts hold the coupler to the transmission plate. I don't know if the aft ones were there for balance or what. I took the forward bolts off and the coupler came off; I took the aft ones off, and nothing came off. I took set screw out, and will need to oil the key way and hopefully just tap the plate with a hammer to remove the rest of the (still broken) coupler from the shaft.

[clausont]

It sounds to me like there is more of a problem than a broken shaft coupling. Mine separated with no torn rubber, but a lot of rust between the rubber and metal. The alignment is not off far enough to be seen or felt but I haven't checked it with a dial indicator.
When I broke mine, I used tie wire (lots of it) to hold the fore and aft sections together long enough to motor to the marina and into the slip, but I would not recommend trying that for more than an emergency repair for very short duration.
I may try something different altogether next winter. I may try to build a hydraulic drive where there is no shaft coupler fixed between the engine and shaft.
I need to think about that one a lot before I try to "re-invent the wheel" so to speak.
It does not appear to be too involved at first thought.

[Psyches]

Well, I'm getting a bit more educated as I go along, and to try and ensure I don't misinform, here's my latest, maybe final update. The summary is though, I'll plan to move to a new coupling style in the future - sooner if I continue having problems, else next year or the year after; I might also have an adapter fit in the interim and use another coupling, to keep from having to haul the boat sooner. But my prop shaft probably needs replacement anyway.

The coupling part number I gave was not complete; the full prp-inc.com part number from farymann is 159-0075 for the 4-bolt flex coupling. I believe that part is rubber metal bonded.

Mine was not bonded on one end, however. It turns out the PO initially ordered a coupling, but prp sent the 3-bolt in the catalog, rather than the 4-bolt with the above part # (not pictured in the prp-inc catalog). So that was sent back, and PO found a fairly new but already separated 4-bolt part locally, and had 4 holes tapped through both metal ends and the rubber, and placed 1/4-20 3" 8-18 ss bolts. The bolt heads were forward, running aft. They sheared off at the aft end. Both fore and aft plates were connected with the nylock nuts and lock washers to the transmission drive and shaft, respectively.

It's still possible I have an alignment problem and I know I have a shaft friction problem, maybe due to the stuffing box (it was almost too loose leaving Sausalito on the "maiden voyage", now it seems too tight after the probs we had on said voyage). There was no problem at the prop or shaft underwater. I had the prop replaced, but the old is still a good backup prop. I may be repacking the stuffing box, and definitely finding and fixing the friction problem (hopefully these are the same), and also maybe tweaking the alignment. But when I get the shaft rotating well again, I'll be trying out the ss bolt solution until my new coupler arrives (est end of May, they are backordered from Germany).

[clausont]

My new flex coupling arrived last Friday. I found that while I had ordered it to be shipped Blue label, they shipped it Red label to be sure that it arrived here by the weekend. The extra cost of the Overnight air shipping was absorbed by PRP - I was truly amazed at this service! I had not mentioned anything to them about this, I only found out about it when I called to confirm that it had been shipped and they told me about the change in shipping and assured me that they were taking care of the extra cost of the shipping.
I installed the coupler the next morning and found that the engine was indeed badly out of alignment (more than 1/8"). It took me about an hour to re-align the engine and finish bolting things up.
I was now excited to start the engine and put it in gear to check the morse cable adjustments I had made and the coupler. So I turned things on (The battery switch was already on by now), hit the starter button and nothing happened except a faint click. Rats! Batteries are dead. How did that happen? Ok, which one of the kids turned on the big work light on the spreaders? Oh, well. Nothing to do now. Dead batteries and no charger that would charge them enough to start the engine.
Wait a minute! There is this hand crank thing here - I winder if I could actually start the engine cold with the hand crank. My oldest one held open the compression release, I twisted away and she let go of the compression release. Bingo! It fired right up no problem!
The long and short of it is all systems are go now. I ran the engine against the dock lines for about an hour with no problems at all.
We still didn't take the boat out as it was blowing strongly all day and I did not want to take the boat out untested with my family aboard in those conditions. Maybe next weekend we will actually take her out.

[Cal2-29]

Originally Posted by clausont

My new flex coupling arrived last Friday. I found that while I had ordered it to be shipped Blue label, they shipped it Red label to be sure that it arrived here by the weekend. The extra cost of the Overnight air shipping was absorbed by PRP - I was truly amazed at this service! I had not mentioned anything to them about this, I only found out about it when I called to confirm that it had been shipped and they told me about the change in shipping and assured me that they were taking care of the extra cost of the shipping.
I installed the coupler the next morning and found that the engine was indeed badly out of alignment (more than 1/8"). It took me about an hour to re-align the engine and finish bolting things up.
I was now excited to start the engine and put it in gear to check the morse cable adjustments I had made and the coupler. So I turned things on (The battery switch was already on by now), hit the starter button and nothing happened except a faint click. Rats! Batteries are dead. How did that happen? Ok, which one of the kids turned on the big work light on the spreaders? Oh, well. Nothing to do now. Dead batteries and no charger that would charge them enough to start the engine.
Wait a minute! There is this hand crank thing here - I winder if I could actually start the engine cold with the hand crank. My oldest one held open the compression release, I twisted away and she let go of the compression release. Bingo! It fired right up no problem!
The long and short of it is all systems are go now. I ran the engine against the dock lines for about an hour with no problems at all.
We still didn't take the boat out as it was blowing strongly all day and I did not want to take the boat out untested with my family aboard in those conditions. Maybe next weekend we will actually take her out.

I have a Cal 2-29 and I'm in the same situation. My flex coupling sheared in half last season. My boat has been on the hard while my marina has made excuses for not fixing the engine. I finally decided to tackle this myself. How hard was installing the flex coupling? Please give me all the details.

Thanks!

Greg