Stern Tube Too long - Extends into Bellows

[Strgzr]

Just replaced my bellows after removing the shaft coupling. Took 3 days to get the coupling off but found the right formula. DO NOT USE THE FLANGE WITH A SOCKET - Very risky there.

Rather bought one of these:
https://www.deepblueyachtsupply.com/5-i ... nge-puller

Used a flat washer and multiple size sockets to push out the shaft. Learned that you need strong grade 5 or grade 8, fine thread bolts and about 20 flat washers. Course threads are painful. - there saved you 2 days if you do this job. BTW, lots of yards use a sliding hammer, VERY BAD IDEA as tranny doesn't like all that banging.

Ok got the coupling off, cleaned up the SS rotor and carefully cleaned up the Carbon FIber - installed new Bellows. Learned that the Stern Tube extends into the bellows - NOT TO PYI's liking - but this is how the original installation was. The Rotor should not touch the back end of the coupling. Measuring for the compressed length, should get about 6-6 1/8 inch. But you start to get into the key-way up close to the coupling. So, a 1/2 shaft retainer color works, but the risk is that the stern tube is inside the ribbed section of he bellows. One could cut the stern tube some but I am not a fan of that idea. Considering installing a thin 1/4 spacer between the SS rotor and the coupling - thereby moving the stern tube section of the bellows forward and out of the ribbed area. Now the original PSS had the stern tube inside the bellows with no apparent chafing seen in the old cut bellows.

Thoughts anyone?
Michael

[wolfe10]

Concerning: "DO NOT USE THE FLANGE WITH A SOCKET - Very risky there". If you are referring to placing a socket between the transmission flange and shaft flange (i.e. using transmission flange as the "backing" to pry against, I absolutely agree. But, what I did was take two 1/8" thick scrap iron plate I had lying around and drilled them in the same pattern as the flange bolt holes. Yes, you could use one 1/4" piece but I did not have one. Stack the 1/8" plates to give more strength and use them and a socket on the shaft flange to "press" the flange off the shaft. Yup, also used grade 8 fine thread and alternated tightening the four bolts/nuts.


Concerning: "Considering installing a thin 1/4 spacer between the SS rotor and the coupling - thereby moving the stern tube section of the bellows forward and out of the ribbed area." Not sure I understand where you are placing the shim. Assume coupling is not the shaft flange, as that would not move the bellows. Am interested in where this spacer would go. Thanks.

[Strgzr]

Thx for the reply.

I have a shaft retainer between the coupling and the stainless steel rotor. PYI advised that under no cirucmstances should he rotor be laying up against the rear of the coupling. Regardless, the keyway is there as well which can compromise the purpus of the forward most O-ring inside the rotor.

THe whole point here however is the shaft log extends into the bellows. This is a concern BUT, this is how the original installation was implemented.

[wolfe10]

Sorry, still don't understand where the 1/4" spacer is and how it helps with "moving the stern tube section of the bellows forward and out of the ribbed area."

[Strgzr]

Looking at the picture - the most forward part is the coupler. Right aft of that is a retaining ring to keep the Stainless Steel rotor from creeping forward and sinking a boat. Some people use jubilee clamps.

Aft of that is the Stainless Rotor, then the carbon fiber which together create a polished surface that keeps water out. Aft of that is the bellows. The bellows is attached to the Stern Tube.

As you can see there is not a lot of shown shaft. PYI states you cannot have the following, 1 - Stern tube inside the ribbed portion of the bellows and 2 - the stainless steal rotor touching the coupling which attaches the shaft to the transmission.

Right now there is a half inch retaining ring there. a thinner retaining ring would allow me to loosen up the bellows at the stern tube and slide it forward thereby reducing the stern tube exposure to the inside of the ribbed bellows. Overall point being the stern tube is long but I am not a fan of cutting it for the sake of the shaft seal.

Hopefully you understand now. think I have explained this as far as I can. Regardless, I wondered if anyone else has replaced their bellows and found the stern tube to extend into the bellows.

Finally , you can rely on the set screws on the rotor but the do slip under pressure and vibration. Retaining collar keeps that from happening.

[Strgzr]

To add, this will be an issue with most C350s that were outfitted with a PSS Shaft seal because the overall length of the working area is very short on shaft working space.

[wolfe10]

GOT IT.

So just going with a thinner ring between flange and SS rotor. Yes, that would allow the bellows to be moved forward a little and still retain the same clearance at the flange. I was picturing ADDING a 1/4" spacer, and couldn't figure out how it would help. Obviously it wouldn't.

And, yes, at least on our 2003 there is very little room between rotor on properly compressed bellows and the flange.

[Strgzr]

Right. Meaning for most of us with factory installed PSS systems, our stern tube extends into the bellows. THis all said, I have found that our engines are not predisposed to move fore and aft much as with higher speed and power engines. Therefore, providing no obvious interruption inside the bellows - meaning push gently on all for sides laterally and look for what I would term "easy deflection", that it may be unlikely, as it has been since the boat was launched, that internal chafing from the stern tube to the bellows is going to occur.

I opened up my old bellows and no sign of chafing. Also I read "again somewhere" that the bellows expand out in circumference when compressed. So I am going to check these things and likely go with what was sent from the factory. I will monitor closely.

BTW, having some rubber bicycle tire inner-tube is part of our "dooms day" kit.

anyway, any thoughts c350 owners or anyone else.

MP

[Outlander366]

I just started the work to replace the PSS dripless shaft and found that the clearance between the transmission flange and the shaft flange was so small that I had to cut away the rubber boot and slide the SS and carbon ring down the shaft. No problem since I was going to change the boot anyway but this has got to be the worst engineered (or was it) maintenance set up I've ever encountered.

I don't understand why the engine could not have been designed to be positioned one or two inches forward of where it now resides. I've been thinking I could do that but probably not a good idea for a couple of reasons. One is the 8 degree drop on the transmission (ZF 15MA). Moving the engine back two inches would probably mess up the current shaft lead in geometry. And second, I understand there are aluminum backing plates where the engine pads are fastened to the stringers. This provides a better holding area than if I just drilled holes in them to re-position them to move the engine forward.

I have one burning question about all this PSS maintenance. What method did you use to get the shaft coupling back on the shaft with so little clearance between the transmission flange and the shaft? Seems to me this is the bigger challenge than getting it off, although that was no picnic either.

Thanks

[wolfe10]

"I have one burning question about all this PSS maintenance. What method did you use to get the shaft coupling back on the shaft with so little clearance between the transmission flange and the shaft? Seems to me this is the bigger challenge than getting it off, although that was no picnic either."

Agree difficult.

What I did was make a "backer" from scrap 2X4's and 1X4's so that force on the flange as the shaft was "driven" forward would NOT, absolutely not contact the transmission flange. Did not want to risk transmission damage.

Lined the shaft key way up and started it on the shaft. Then installed the backer and my brother beat the propeller end (yes, out of the water) with a sledge hammer onto a 4X4 so he would not harm the prop. I had measured how far onto the shaft the flange needed to go and he kept hitting until it reached that mark.

Not a job for the faint of heart, but I could not come up with any way to "pull" the flange onto the shaft/nothing to pull against.

[Outlander366]

I've been thinking that's how it could be done. You must have used the 1x4 between the transmission flange and the shaft flange as I don't think a 2/4 would fit between them. Is that correct? There is that little bulkhead where the transmission fits through to the shaft. Is that where you positioned the 2x4s?

Wouldn't have any pictures of the set up would you?

George

[wolfe10]

Sorry, no pictures. And this was long enough ago that I do not remember exactly what I used where. Likely even some scrap small pieces of plywood and 1/8" thick aluminum flat stock I had in the garage to increase spacing as the clearance increased.

Certainly as the shaft was driven onto the flange, there was more clearance between the shaft flange and transmission flange, so "shimming" increased.

[Outlander366]

Thanks for the info. I start this process next week and with any luck will complete it and get everything back together.

I'll try to take pictures of my setup especially if I think of some other method to get the work done.

George

[KenKrawford]

Next time I replace mine I’ll probably use a split coupling similar to this - https://www.getaprop.com/hurth-split-coupling-4bs
It would solve the “lack of clearance” problem trying to get the coupling back on the shaft.

[wolfe10]

Sorry, Ken, that is cheating. It would make the job too easy.

No MacGyver points for that one.

[nybor]

Hi. I installed my pyi many years ago and now have to do it yet again ()%)+$@&%^)+$@&^%+)*%&)$&%)&
I am not at the boat but just want to make sure of the dimensions before ordering a new unit.

The shaft is 1 inch. Is the shaft tube 1.5"?

Thanks

dave

[Strgzr]

Ok guys, good replies.

First, split coupler is ok and I actually bought one but did not use it. First, this would have necessitated drilling a new locking screw divot in the shaft as a split coupler is shorter in length. Second, a split coupler must be faced, or put onto a lathe which some say would include being with the shaft attached. Latest person I spoke to however said facing a new coupling does not need to be accompanied with the shaft. BTW, taking the shaft out involves dropping the rudder. Options there are 1 - dig a hole or 2 - do the work with the boat on the travel lift. I re-used the original coupling taking care to ensure I kept the alignment with the flange the same. I had to re-tap the lock bolt holes a little to get the threads to accept the square head lock bolts.

Finally installing the shaft in its original orientation involved light tapping on the prop with a rubber mallet. any other orientation and it would not go. Once I got it nearly flush with and the divot holes lined up, I tightened up the lock bolts. Forgot to mention I oriented the key in the 6 O'clock position so it would not slip out. But I checked to ensure it stayed inserted into the keyway. I used soapy water to make all this work. Finally I tightened up the flange bolts to 40 ft lbs. Don't know if that was correct but for a 5/8 bolt that was the torque spec. So it can be done without dropping the rudder, moving the rudder etc. I plan to keep a tight eye on this until confidence is regained. Note, the keyway is visible about 1/4 way past the afte end of the coupling. I used a small Allan wrench to tap inside the keyway to ensure the key was there pror to tightening up the divot locking square head bolts.
One final note, some areas of he flange clearance looking for .004 of an inch depends on how much face surface prep you do. Because this shaft on the 350 is so short, and the prop turns easily, I am going to look for excessive vibration. If comparable to previous installation, I am calling it a day. One final final note, I replaced the maralon water feed and purchased lots of little set screws. One final final final note, go easy on the rubber O-rings. I used soapy water. Do not use any grease or silicon as it will dry-rot the rubber. Soapy water only. Finally, finally, finally, I painted the whole area with epoxy which makes for easy cleaning. Apparently our bilges are done in gel coat. so moral of that story is you can paint epoxy over gelcoat but you cannot gelcoat over epoxy. Ops but really, so what - more epoxy if needed. OUT!!! MP C350 #275

[Strgzr]

2 inch stern tube. 1 inch shaft.

[Strgzr]

Sorry, third response post here. Note I put a blue shop towel between the carbon fiber and the stainless rotor during all maintenance actions to preclude any incidental damage to the mated services. Also, I was advised by PYI not to overtighten the hose barb as it will crack the carbon fiber. Word of caution there.

[william vanwagoner]

The last time this job was done on my C350 the yard removed the shaft but did not need to drop the rudder. There was sufficient deflection allowing them to slide the shaft alongside the rudder. They also used a split coupling which has worked well. I will be replacing the bellows again in about a year and am thinking about replacing the split coupling with a Sigmadrive which functions like a split coupling with a universal joint function allowing up to 8 degrees of deflection pretty much eliminating fine engine alignment adjustments. Has anyone tried the Sigmadrive on the C350?