# Installing prop shaft flange/transmission coupling



## jimgo (Sep 12, 2011)

I need to replace the stuffing box hose on my boat. After nearly 9 hours of prying, oiling, heating, banging, and a lot of swearing, I have everything apart. I had to cut the flange or transmission coupling (or whatever it is called, I'm going to call it a flange 'cause that's easier to spell) off the shaft, because it just was NOT coming off any other way. If you want all the gory details, they are in my blog.

Anyway...I now have the new flange, and I'm planning on taking it to be fit and faced to the prop shaft, which I hope will happen this Friday (unless I can find a shop in the Philadelphia, PA area who can do it sooner). Then I get to re-install the shaft in the boat. I can't install the shaft from inside the cabin, the engine is in the way. That means that the flange has to come off again after it is fit and faced to the shaft. Then, when the shaft is back in the boat, I need to reinstall the flange. I assume it's going to be a pretty tight fit, and alignment is going to be tough, too (I will need to match the flange with the holes in the shaft for the set screws). How do I do this inside the engine compartment? 

In theory, a block of wood at the propeller end of the shaft and some good hits on a hammer should help drive the shaft into the flange. But what keeps the flange from sliding forward in the boat? I don't want to attach it to the transmission out of fear of damaging the transmission, and I don't remember seeing any other protrusions near the shaft log that I could use to help keep the flange from moving. So, how do I get enough force to be able to do the install?


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## Alex W (Nov 1, 2012)

If I were having the prop shaft pulled and machined I would consider asking for a 5/16" or 3/8" thread down the center of the prop shaft that could be used along with a draw bolt and plate to pull the coupling onto the shaft. In a 1" shaft that would not reduce the strength and it would make installing the coupling a lot easier. On almost any lathe this is a roughly 10-15 minute job.

My boat seems to give me much better access to the prop shaft than yours. I used a split coupling and fought with it a fair amount to get it installed. A nut and draw bolt would have saved a lot of work.


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## Dave_E (Aug 7, 2013)

Hey Jim,

I just read your blog. I have to do virtually the same thing next week, except I'm replacing the dripless shaft seal (instead of your traditional stuffin). So after your discovery of the woodruff key and a non-tapered shaft, could you have done it without cutting? My coupler is a solid rust looking thing and now I'm getting nervous. What is meant by "fit and faced", and if my shaft does come off (cross everything ) Other than cleaning it up, do you see anything else i would have to do on re-assembly?

Dave


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## capta (Jun 27, 2011)

Since you have the locking bolts and indentations in the shaft, I don't see why you need such a tight shaft/flange fit. I would advise that the two go together fairly easily (obviously not loosely) and that you use NeverSeeze on everything, so you don't have this problem again. Be sure to have the machinist drill small holes in the locking bolts for the seizing wire.


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## jimgo (Sep 12, 2011)

Capta, the bolts that came with the new flange have the holes in them, but thanks for the reminder! Where can I get Never Seize? I've heard of it and a few other compounds, but haven't tried looking for them yet. Would it also work on the outside of the packing gland to help keep the copper from corroding?

I need to test-fit everything and see how hard it is to connect. If its tough, I like Alex's idea and will talk to the prop shop.

Dave, I'm glad the blog posts are helpful for you. I know I probably go into too much detail, but hopefully it gives you some insight into the issues I faced and how I solved them. I can't say what I did was "right", but it worked.

According to Maine Sail (see the first several parts of this description), when you get the flange off, if it has been on more than a year or two, the rust inside the flange actually distorts the inside of the flange. When you then remove it and clean it up, you lose some of the metal from the inside of the flange. The result is that the fit isn't what it should be if you try to reinstall them. So, you are better off replacing the flange rather than trying to reuse it unless the flange is fairly new. When the flange is replaced, the flange should really be matched to the shaft so that the face of the flange is perpendicular to the rotational centerline of the shaft. This reduces vibration as the assembly spins. Each shaft, especially older shafts, is slightly different and thus they really should be matched. That's where the fit and face comes in. Or at least that's my understanding of the process.


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## jimgo (Sep 12, 2011)

BTW, I assume you've seen this one:
Re-Packing A Traditional Stuffing Box Photo Gallery by Compass Marine at pbase.com


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## capta (Jun 27, 2011)

jimgo said:


> Capta, the bolts that came with the new flange have the holes in them, but thanks for the reminder! Where can I get Never Seize? I've heard of it and a few other compounds, but haven't tried looking for them yet. Would it also work on the outside of the packing gland to help keep the copper from corroding?


NeverSeeze can be had at any auto parts store. There are at least two kinds, a grey one for iron and steel and a copper one for stainless steel and aluminum. Both are useful on a boat.
There is no value in using either on bronze; the green color really doesn't affect the integrity of the metal; just wire brush it every so often. The NeverSeeze goes on the threads and again, has no value as coating of a steel surface. If you'd like to lessen corrosion, paint the flange and bolts with zinc chromate after assembly, but really, just wire brushing it and spraying with PB Blaster should keep it in good shape. The big deal here is not to let salt water get on the drive train inside the boat and rinse with fresh if it does.
Don't forget that aligning the engine to the shaft flange is your last step. It really is an important step, though it is a huge PITA. Free up all the engine mounts (again NeverSeeze) and make sure you have whatever tools you'll need before you begin. If you've had any noise from the drive train, under way, you'll be surprised the difference the alignment makes.


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## Alex W (Nov 1, 2012)

I did not get my prop shaft machined. I put on the flange and measured runout using a dial indicator and it was within tolerances, so I left everything alone. Pulling the shaft on my boat requires dropping the rudder, and I wasn't prepared to do that.

I did use a split flange coupling and it was still a very tight fit.

I made my own remover instead of using a gear remover. It was pretty simple and could be made with a hand drill and a 1/4" piece of steel, but is a lot easier to make with a drill press or milling machine (which is what I used). It looks like this:
https://scontent-b.xx.fbcdn.net/hph...=9abfdf2d5a06a2bda67a0437dfad42c7&oe=53DA96FD

The 4 outer bolts match the bolt pattern of the flange and are through holes on the plate. The inner one is tapped and pushes on the prop shaft to push the flange off. It worked very well. I would be willing to loan this tool to people in Seattle if they don't want to make their own. It is for a Yanmar 4" coupling.


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## jimgo (Sep 12, 2011)

I think you mentioned that in another thread, Alex. It looks like it would basically do what my gear puller did, but with less of a clearance issue than I had.

How did you measure the run-out? Did you mount the shaft on something and spin it? I don't have a dial gauge, so this might be a bit of a moot point. But still, I'd be interested in how you did the measurements. If the whole thing is within spec, that would save me a lot of time and trouble.

I do need to replace the key for mine. Any idea where to get one?


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## Dfok (Apr 11, 2010)

capta said:


> Don't forget that aligning the engine to the shaft flange is your last step. It really is an important step, though it is a huge PITA. Free up all the engine mounts (again NeverSeeze) and make sure you have whatever tools you'll need before you begin. If you've had any noise from the drive train, under way, you'll be surprised the difference the alignment makes.


Is aligning the drive train something best done in the water? I know the shape of my boat changes just a bit when it is sitting on keel and stands in the yard ( the head door won't close till I'm back in the bay).


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## Alex W (Nov 1, 2012)

jimgo said:


> I think you mentioned that in another thread, Alex. It looks like it would basically do what my gear puller did, but with less of a clearance issue than I had.
> 
> How did you measure the run-out? Did you mount the shaft on something and spin it? I don't have a dial gauge, so this might be a bit of a moot point. But still, I'd be interested in how you did the measurements. If the whole thing is within spec, that would save me a lot of time and trouble.
> 
> I do need to replace the key for mine. Any idea where to get one?


Square key stock is a standard hardware store item around here.

I measured runout by clamping a dial indicator holder to some part of my boat (I don't remember what exactly) with the dial indicator against the prop shaft. I turned the shaft by hand to measure. This is how you would also measure runout on something like a drill press chuck.


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## three-quartertime (Nov 5, 2012)

Yep, the boat should be in the water when aligning the engine.


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