shaft coupling replacement questions

[RonRelyea]

I need to replace a very badly corroded shaft coupling on my Hunter Vision 32. The current setup has some unknown brand of flexible shaft saver and a 4" diameter coupling on my 1" shaft. The coupler has a through-bolt and I don't think it is keyed (if it is keyed, it is corroded so badly I can't see it!)

I can't seem to find an identical coupling anywhere .. does anyone have suggestions where to find one?

Also .. am I nuts for trying to do this myself? I need to get the coupling off in order to repack the stuffing box. Local Marina will put me in the sling and leave me there over the weekend so I can work out of the water at a more liesurely pace.

Question about the through-bolt ... my plan is to hacksaw off the nut(s) and/or bolt head to get the through-bolt out. Are there any threads inside the coupling that would make that a dumb idea to try? Then the plan is to remove the shaft saver and use a long socket against the shaft and draw the coupler off the shaft by using longer bolts to the engine side coupling.

I'm considering installing a PSS shaft seal ... but there is barely 7" from the end of the coupling to the shaft bearing exiting the boat. Comments??? I'll also call PSS ..

I've got a case of PB Blaster ;-) and have already started application

I'd be grateful to hear from all the experienced folks as to whether #1, I should try this myself at all, and #2 any tips / tricks / caveats / preparations to make etc.!

Thanks!

 

[Ross]

I would start pecking at that coupling with a chipping hammer and find out exactly how bad it really is. It looks crappy but steel is like that. the output flange on the transmission doesn't look any better. Chip away the rust and if it is still mostly there treat it with phosphoric acid and paint it. I don't think there is room for a PSS system.

 

[Steve Dion]

Sawzall!

 

[RonRelyea]

Hi Steve ... I DO have a sawzall!!! are you suggesting using it on the through-bolt or the ENTIRE coupling??

Anybody know where they sell the through-bolts that are drilled to accept the stainless steel retainer wire??

 

[RonRelyea]

Ross ... thanks for the tip ... I'm worried about the rust being inside the coupling too ... would there be too much free play with the shaft if the inside is corroded and that corrosion is removed?

 

[kenn]

Anybody know where they sell the through-bolts that are drilled to accept the stainless steel retainer wire??

If you use a new Nylok nut and/or Loctite on the new through-bolt, the ss retainer wire shouldn't be necessary.

of course if you have a couple hours and a box of drill-bits to kill, you can always drill the bolt.

 

[Ross]

McMaster-Carr sells drilled bolts and locking nuts but not drilled nuts.

 

[tommays]

The issue i see is that IF you get the old one off in one piece after you clean up the rust it will be to lose on the shaft

If you can get the driver saver off can you replace the packing without trying to pull the coupling ?

 

[Ross]

You should be able to pick the old packing out of the nut without removing it from the shaft.
This is from McMasterCarr:
<LI class=PageHdrNm>Seal Installing & Extracting Tools

Packing Seal Tools with Interchangeable Tips
Flexible Shaft with Corkscrew Tip
Corkscrew Tip
Brush Tip Use these extractors with interchangeable tips to create an efficient system for removing packing and lantern rings and cleaning stuffing boxes. Suitable for use in packing that's wider than the tip diameter. Extractors and tips are made of steel.
Flexible-shaft extractors have a cable in the stem that allows a slight bend for better access to packing. Rigid-shaft extractors are for dense packing that doesn't break up easily. Corkscrew tips screw into standard packing for easy removal.
The interchangeable tips thread onto the extractors. Wood-screw tips are designed for removing hardened packing. Use brush tips to clean the stuffing box. Lubricating-ring tips permit easy removal of threaded lubricating rings.
Rigid Shaft with Corkscrew Tip
Wood-Screw Tip
Lubricating-Ring TipExtractors— Include One Corkscrew Tip

Flexible Shaft

 

[Maine Sail]

Ron,

Please be very careful removing this coupling. Often times they need to be cut off or the shaft cut and replaced along with the coupling. You run a very real risk of breaking the transmission output shaft so do not over tighten the draw bolts. Through bolts are no longer SAE or ABYC standard practice for shafting with a striaght coupling. The method used today is a key with two set screws and a tolerance of .001" or better, .001" is the absolute worst it can be to meet the ABYC P-06 standard for shafting, for the coupling to shaft fit.

This guy got very lucky that the coupling fractured and not the output shaft flange.. This coupling was finally cut off with a die grinder over the key way.

Oh and even if you do get it off there is a very, very high, perhaps over 95%, chance that the couplings tolerances have been toasted by corrosion.


P.S. DO NOT get PB Blaster anywhere near the transmission out put seal or you will be looking at removing the gear box and R&Ring the seal. PB Blaster eats these seals for lunch...

 

[RonRelyea]

loose shaft / coupling fit due to rust

The issue i see is that IF you get the old one off in one piece after you clean up the rust it will be to lose on the shaft

If you can get the driver saver off can you replace the packing without trying to pull the coupling ?

Tom ... yeah, this is what I'm afraid of and why I'd like to install a new coupling. But I've subsequently done some reading of other posts, especially from Maine Sail, regarding the importance of the fit of shaft and coupling. Is it prudent to just get an off-the-shelf coupler and tap it on??

As far as the question about just leaving the coupling in place ... I can't get the packing nut backed off the threads - no room - it hits the coupler ... as in this picture ... (ignore the packing between the nut and the coupling - that's just a jury-rigged temp fix to stop the drips!)

Anybody able to point me in the direction of a new coupling with the through-bolt?

 

[Maine Sail]

Anybody able to point me in the direction of a new coupling with the through-bolt?

Likely a machine shop custom job which might make it a lot easier and less expensive to do a new shaft and coupling. Ron Peck at New England Propeller is about the best I know and he has FAST turn around and can ship anywhere.

I don't know of a single shop stocking through bolt flanges they are all keyed now to meet current standards and made by companies like Walters or Buck Algonquin. I know Buck Algonquin does not make through bolt couplings just; standard straight, split straight, and standard and reverse tapered couplings but all these couplings are keyed.

Before you can begin to locate a possible replacement coupling, if there is one out there, you need to know:

1) What is your gear box model (It looks like a Hurth/ZF)

2) What is your shaft diameter and how far from the end is the through hole center and how far in from the face of the coupling, if at all, is the shaft set back..

 

[Steve Dion]

I would start by cuttiing off the bolts, but it may take cutting the entire shaft.

A new shaft is about $100/ft installed (guesstimate), plus coupling, seal etc.

 

[bobtigar]

Couplers are not boat standardized, they are standardized by dia of the coupler and shaft size. Most marine transmission distributors carry them. They are sold as halves, meaning you can buy the portion that fits to the shaft if that's all you need. That saves removing the portion on the transmission, if it is ok. I purchased 1 coupler half for about $40. If you cant find it locally, I can provide a dist in Ft. Lauderdale that will ship. Bob

 

[BobM]

I did this job on my 30 footer. After everything I went through if I had to do it again I'd have them put the boat on the hard and plan for two weekends of work (no way you are going to get it done in slings over a weekend in my opinion, unless you order all new parts and get really lucky). The following is my experience doing this job one time and from memory. It is meant to give you a good overall idea of the scope of the job. It is certainly a doable DIY job and will leave you with a much greater knowledge of you boat. It can be time intensive, especially if you dissassemble rather than cut the shaft. I think it took me four weekends to deal with a stuck propeller, press the coupling off, replace the cutless bearing and reassemble. Please research this topic on the site and pay attention to all the corrections / opinions that this post will likey generate!

Order all new parts...coupling (with a split it in parallel to the shaft to make it easier to mount), shaft, correct hose and packing for the stuffing box and cutless bearing. Pull the prop if you can, otherwise if you can fit it out past the rudder you can leave it on (mine wouldn't come off for love or money) Cut the old hose off to give you room to get the sawzall in. Cut the shaft. If the prop is still on the shaft mount a piece of tube less than the diameter of the props center in a vice and place the shaft with prop in the tube. Spin the nuts off until they protect the end of the shaft then honk on them with a hammer to knock the prop off.

The beauty about tossing everything is you can forget about the through bolt and just unbolt the coupling. I spent $400 at a machine shop and could have spent less for new (about $300 at www.deepblueyachtsupply.com) . The only thing I gained is having the machine shop balance the prop on the new shaft as a rotating assembley and test fit the coupling to the shaft, which is something you can have one do anyway. Clean and repack the stuffing box and fit the nut and the hose on loosely for now.Then replace the cutless bearing (follow Mainesail's excellent guide), lube it with water and insert the shaft through it and up into the stuffing box.

Having a split couplling makes mounting it on the shaft easier. I spread mine a little with a chisel to make like easier and then placed a board across the back of the transmission coupling to allow me to tap the coupling on more easily. You don't want to hammer on the output shaft of the transmission as you might damage it. I made the board up so the force of the hammer blows was transferred to the engine mount beds instead, as they are well secured to the hull. It took just a few decent taps (nuts on to protect the end of the end of the prop shaft again) to drive mine on after I fit the key in place. Tighten up the two bolts in the split coupling to close the split. Insert and tighten the two bolts that hold onto the shaft (in lieu of your through bolt) and safety wire them together. Then you can fit the prop back on and bolt it on.

Inside the fun really begins. I keep asking Maine to write an alignment treatise, but given the complexity of the topic I don't blame him for holding out ;-) Being sure to keep the cutless bearing lubed with water and the packing nut off/loose, pull the new coupling half and shaft up to the transmission coupling half as closely as possible. Adjust the engine mounts as required to line the two faces up as parrallel as possible in all respects and so that the rims of the couplings are lined up. Rotating the shaft may help. Bolt the coupling halves together tightly then check the tolerance all around the coupling with a feeler gauge. Adjust the engine mounts sparingly, if necessary, with a goal of getting withing 0.005 of an inch eventually. I say eventually, because you can ultimately only do this final alignment when the boat is back in the water and has had a day to relax to whatever dimensions it normally has while afloat. Blocking a boat does change things, in my experience, so you can't do a final alignment on the hard. I was within about 0.025" when I launched. Tighten up your stuffing box hose and nut.

Once launched recheck and realign as necessary to get to 0.005" and loosen your stuffing box nut until water comes in to burp out any air inside. I didn't do this initially and hear a ringing sound that was, in hindsight, likely due to my running the stuffing box dry. It stopped after I removed the nut and let some water in then retightened it. Initially the liquid I had dripping from my stuffing box was melted wax!

 

[redhead78]

Hey guy,s I just went thru all this basically the same with my repower. I am not familar with your engine room and stringer setup, last post sounds right on. With all you have going already can you move engine forward a couple of inches? That would help you with some of your stuffing box issues. Red