PYI DSS rotor diameter

[STB]

PYI DSS rotor hole diameter

Hi all,

The yard went to install the maintenance kit (bellows, o-rings, and clamps) for my PYI dripless shaft seals and decided the stators (carbon part attached to the bellow) and rotors (stainless steel part attached to the shaft) weren't in good shape and ordered full replacement kits. I wasn't involved in this decision, but am never one to mess with something that keeps the water out of the boat, so I was okay with it.

They went to install the new kits and couldn't get the rotors onto the shafts. They ordered a new set of kits. I wasn't involved in that decision either. That set of rotors had the same problem.

They determined that they were all made out of spec and sent the old parts and the new parts to a machine shop, instructing the shop to either resurface the old rotors or to make the new rotors match the specs of the old ones, as the machine shop determines is best. I wasn't involved in this decision either, other than that they introduced me to the courier on his way out the door at the end of the day as I was on my way in the door to check on progress.

Their hypothesis is that we have 4 brand new rotors, from 2 different distributors, probably made at different times, out of spec. Having said that, they couldn't tell me what the rotors measured, what the shafts measured, or what the difference was. They just pulled a caliper out of an old toolbox, adjusted it to some measure, and told me they were both "like this."

I became concerned that the problem could possibly be that the shafts could possibly be 45mm, the "metric equivalent" of 1-3/4", which is a hair larger. I didn't have my calipers nearby, so I bought two new ones, calibrated them, and measured the shafts in the area of concern and elsewhere. They couldn't be more perfect 1-3/4". The error was in the thousandths. The old rotors were also stamped 1-3/4".

So, now I am trying to figure out what to do. I think my options are...

Let the yard continue to solve the problem. They are actively working on it. They aren't putting it aside, slow walking it, blaming anyone else, or anything. They are doing their very best.

Another option is to set some parameters. In particular, I could insist that they get the new rotors to work rather than resurfacing the old ones, etc.

Another option is to go down to the shop, measure the parts myself, and see 1st hand what is going on, especially since I measured the shafts, which they did polish to a jewler's shine. From there I could make a decison about old vs new or decide not to make a decision.

Another option is to go to the shop, verifty the rotor hole diameters, and after verifying that they are 1-3/4", take them back to the boat and try to install them myself. Since I don't believe all 4 were made wrong, I figure it just has to be a tight fit. I'm figuring I could ice the shafts for 2 hours, heat the rotors to 120 degrees, and then see what happens with the install. I figure it has to be a tolerance stacking problem. But, of course, if I don't succeed -- this won't have made me any friends at the machine shop or yard.

Or, I could switch shaft seal brands, but the other brands are lip seals, and I tend to not like those since they use a moving seal at the shaft vs rotor-stator interface.

Or, I could back out of all of this and ask them to install a conventional box, which I like, anyway.

Maybe there are more options I'm not thinking of...?

For what it is worth, the yard has been around decades, has a sterling reputation, and they've had all of their "lead" people in the boat studying the problem and trying to sort it out. They aren't hiding, ignoring, focusing on other things, etc. They are being professional about it in every respect (other than, perhaps, calling me before making decisions, but I haven't pushed back on that).

Any thoughts?

Many thanks!
-Greg

 

[tiltrider1]

The old saying, Trust but verify. That is exactly what I would do. Something seems fishy but I would hate to put blame on the wrong party. Measure everything yourself and then you will know all the answers.

 

[firehoser75]

The old saying, Trust but verify. That is exactly what I would do. Something seems fishy but I would hate to put blame on the wrong party. Measure everything yourself and then you will know all the answers.

+1. Verify.

Something is definitely "fishy". I find it hard to believe that PYI missed "getting a fit" for a shaft that does measure 1 3/4 inches four times. Possible if a whole run went bad, but?

 

[twistedtree]

Has anyone called PYI? If you shaft does indeed measure 1-3/4", and the rotors don't, then PYI should be making this right. You shouldn't have to buy two sets of parts then pay for a machine shop to fix them.

 

[STB]

The yard did call PYI. They reportedly don't know or expect there to be a problem with the parts, but offered to do anything in their power to get the parts needed to the shop, including paying any nearby dealer with anything we need in stock for whatever it is we need, even if it means breaking kits for a single part, etc. They also apparently offered to pay for the machining if it is demonstrated that their parts aren't to spec.

Not sure how the story will end. If it is a tradesmenship issue that is made easier by the machine shop relieving some metal. PYI could say existing parts /should/ fit. Yard could say they don't. Shop could relieve some metal 2ith fingers pointing. Hard to say.

 

[Solly]

The stationary part on the bellows should have a good bit of clearance. Shouldn't even be close to rubbing. The rotating collar on the shaft has O rings that slide over the shaft to seal. Are they using lube to slid the collar on the shaft ?? Right size O rings ??
Nothing to machine there.

Sounds like the wrong size kit or not following the install procedures. Double check sizes and part numbers to be sure.

 

[STB]

I did check the part number against the catalog and log and shaft measurements. It was the right part number. The stainless rotor is also stamped 1-3/4".

I wasn't there to see what they tried. I saw a thing of their dishwasher liquid on the boat. I can only assume they tried lubing it with that, as per the instructions.

 

[STB]

Hey Solly,

I checked the part number -- the part number was for the right sized kit and the 1-3/4" shaft diameter was stamped on the part, itself. I saw they had a bottle of dish soap in the boat, so I can only assume they lubricated it.

I'm going to try to go in the morning and see the "other" set of rotors they ordered and should be there. I wonder if they lubed the shaft, but not the o-rings.

 

[STB]

So, for anyone curious how the story ends...

The machine shop resurfaced the old stainless rotors. They were reinstalled today with new o-rings. No problem with the install.

I asked to see them before install, but, of course, they were reinstalled without them letting me do that. I pulled back the bellows and they looked good to me.

The thing that frustrates me about this is that, from the very beginning, I thought the old ones were fine and needed minimal machining. I had bought a maintenance kit. But, I was told I was wrong, they were too far gone, and they needed to install new everything. Then, suddenly that doesn't work and I'm told they are plenty good an just need to be machined -- but we still need the new kits because my old carbon stators, which looked perfect, were "brittle". Sigh. Probably just $500 of my money they spent for no reason.

As for the reason the new ones didn't fit, it appears to be a tolerance problem. I measured a section of my shafts at 1.7540" +/- 0.0010". I called PYI and they told me they currently machine them to 1.7540", but didn't have a tolerance on that or specs going back 20+ years. The upshot is that it was just too tight, at least without doing things the yard wouldn't do, e.g. heat and cool.

As for the old ones, the machine shop said they appeared unaltered, but had a slightly larger diameter. They were 20+ years old, so the tooling probably changed and got tighter since then.

The metric model apparently would have fit and been okay, but the yard was going to charge me extra days to wait while they got sent in and the old ones never looked bad to me.

As for machining the new ones, the "machine shop" was actually a prop shop and didn't have tooling to deal with the diameter and o-ring groove, just the face. So, adjusting the new ones wasn't an option and the yard wouldn't let me adjust them by hand. I dont think they expected me to be successful and wanted to keep them returnable.

We'll see how much this adventure costs. I splash in the morning. Haven't seen an invoice, yet.

 

[Ski in NC]

I too have seen shafts slightly out of spec one way or another, and it does cause problems. When dealing with a couple thou out, you really need to use a micrometer checked against a standard and not a caliper. Although the caliper can be ok if checked against a standard. Not sure what was used there.

But when I first read this, my first go would have been to renew the face of the SS rotor and replace the bellows and carbon ring/seal body. There is a bushing inside the seal body that if it wears it will cause trouble.

No idea what was done on original fit up. Yard guys (especially in Asia) can get mighty creative. Could have just popped the orings out of the rotor and run a small cylinder hone through the bore to knock out a few thou.

For the yard to do quality shaft work, they really need on hand a few good mics and standards. Otherwise they are doing guess work and you really should not pay too much extra for this.

But in their defense, I'm using my pretty good hindsight!!

 

[Solly]

I was on the PYI site this morning and they said neither the rotor or the stator should need replaced in normal use..... Maybe some normal wear where they mate during breakin.
Anyway at least everybody was working towards a solution. It's done and hopefully all good. The peace of mind will be worth it !
Might as well look at the positive.

 

[bluebyu]

Thanks for the update.

Sad PYI would not share the tolerance. Guaranteed the lathe/CNC operator has a print with a tolerance!

 

[STB]

Hi Ski, Hi Solly, Hi Blubyu, Hi all,

Ski: Both the yard and I were using micrometers. My boat and I live different places and some tools I have in both places -- and others in the wrong place. I had to make do with what a quick trip to Lowe's could get me. But, I was able to borrow a gauge set and calibrate it. It was within stated accurace on the gauges and precise in use.

I really think PYI just made the diameter larger years ago. Maybe they used the metric part for both imperial and metric shafts. In my way of thnking, between the set screws and back clamp it shouldn't be a super critical measurement. And, forwhatever a one white mouse experiment is worth, the old ones lasted decades -- and apparently will last decades more.

You made me feel better about having replaced the carbon stators. It turns out they charged me $500/shaft for the full kits. So, replacing those cabons cost me $700 for parts vs just refacing and using the maintenance kits. And that isn't counting the $252 in extra days of "storage fees" while the boat say on the dry as they made phone calls and waited for parts. I still donm't buy them being brittle. They looked like the day they were made to me.

Fortunately, they didn't seem to charge me for the phone calls. On the flip side, I asked them to replace my 8 swim step nuts and bolts. And, that apparently took 2 people 4 hours each for $800 plus $32 in parts. They made their own washers, calling them "backing blocks"! Sigh. The diver and I could have done it for $132. I wasn't thinking when I asked -- it ust popped into my head and to their checkbook it went!

All in all, this was a good yard experience. The bill was $1200 over my mental calculator for the work -- and that is less than $1000 for the kits, $700 over my mental math for the swim step, and extra $250 of storage put together. So, the situation with the DSSs, which was a PITA situation, I really should have just swapped the swim step bolts myself. Me asking them to do that was as silly as them making their own washers.


Solly: Indeed. So right you are! I feel good knowing the water will stay on the right side of the hull -- the outside!

Bluebyu: In PYI's defense, I don't think they were holding back. I think the product manager gave me whatever he head readily available. And, if I'd asked him to chase the tolerances down, I suspect he would have. They seemed very first class and spent a lot of time talking to me and the yard and they offered to own the whole situation if the machining was bad. But, once I heard the spec, I knew that even we weren't even good nominal, so they didn't matter.

The time that was lost was lost because the yard really didn't have reasonably accurate, reasonably precise measurements to give them or they would have probably called it what it was earlier. The yard was just treating their micrometer like a tape measure.

They didn't mean to be sloppy. And, within the context of what they do every day, they weren't sloppy. They were skilled marine generalists, not machinists. If the yard had a machine shop on site, and a machinst was measuring, it might have gone differently. O an engine builder. Or even an vehicle brake technician. But, they had the trades they had and did the best they could with them.

I really can't complain. The work was done right. It was done neatly. They mostly put up with me running around with a micrometer and chasing after them with the machine shop(prop shop) and PYI. They didn't slow walk the job when it got involved. They followed through. They let me do thing on the boat while it was there (except Sunday). They dropped cloth and towels and took off their shoes while working to keep things neat. The invoice was fully itemized and accurate to the screw.

If someone did something wrong, it was me, not insisting that we just use the maintenance kit as planned. But, I have a policy on things that keep the water out and the smoke in -- I'll replace anything that anyone credible looks sideways at. To me, if there is a difference of opinion on that stuff, it isn't worth being right "most" of the time. Even in Florida's shallow waters -- 4 feet is enough!

Thanks for the feedback everyone!

 

[Solly]

FWIW. I just payed almost $ 500 to have the shaft packing replaced on the Mainship. $450 of that was labor. I told the yard going it would be Royal PITA to do. I could see the shaft gland and I could touch it. But not both at the same time. 68 and 240 lbs. I just didn't fit. Needed a young, little guy to get in there. Plus they said they needed to make a tool to use doing it.
I'd like to have the S.O.B who thought putting a 200 gal. diesel tank on top of the gland a good idea strung up by their toes upside down and let them replace it.

Not blaming the yard a bit ! It's done, just needs adjusted when we launch so it's all good.