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Author Topic: Shortening the drive shaft for new transmission  (Read 409 times)

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Ron Hill

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Re: Shortening the drive shaft for new transmission
« Reply #15 on: July 18, 2022, 01:58:31 PM »

Kyle : Re read my post and I said that a Flexible Coupling does NOT need a keyway!! 

What I did while in the water was to pull the drive shaft all the way forward so the prop was against the strut, then push the shaft back 1 " !!

A few thoughts
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kable

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Re: Shortening the drive shaft for new transmission
« Reply #16 on: July 18, 2022, 07:37:54 PM »

KWKloeber - Yeah, I usually do have plan B and C.  In this case, I don't and I don't have enough knowledge of the dripless PSS.  My local mechanic that did a great job replacing my cutlas, new stainless shaft, prop etc. really really recommends me pulling it for exactly that.  He said he has done it but it is him.  Starting to think I should pull it... but then... more "while you are at it projects" will creep in... $$$

I guess I head read that people put a clamp on the dripless when pulling the trans/engine.  That keeps things compressed and not much water inflow.

Now, of course I need to pull the shaft foward, hit the strut and move back (thanks Ron).  To do this, I need to remove the clamp.  I do have helpers, is this something you can hold pressure on by hand while we quickly adjust the shaft?  Worst case, plan B, clamp clamp??? 

Or should I just pull it out?

Now everyone has me scared that how do I know when I re-launch it is not going to flood, since clamping wasn't good enough in the first place.  Regardless I guess I need to research the PSS and the set screws that I need to replace etc.
« Last Edit: July 18, 2022, 07:39:10 PM by kable »
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1988 C34 #785 SR/WK Universal M25XP - "As We Wish" Bellingham, WA - San Juan Islands

kable

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Re: Shortening the drive shaft for new transmission
« Reply #17 on: July 18, 2022, 08:49:12 PM »

Ugh.....
Going back and forth...

So it sounds like people replace their trany in the water w/ a dripless PSS by installing a clamp (I think to keep the spring tension in place).  So I assume when you remove the transmission the shaft is free and that is why you loose the tension in the PSS spring).  So they have it clamped, put in the new trany and good to go (maybe there is new setscrews, not sure).

So the difference for me, is that I need to pull the shaft all the way in (hit the prop on the strut) then push back out 1".  So to be able to move this I need to remove the clamp, which will cause the spring tension to go away and water to flow in.  So can I keep the tension on another way (holding it etc?).

So what would plan B be?  For the people placing the clamp, what would their plan B have been?
Not challenging, actually looking for a plan B.
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1988 C34 #785 SR/WK Universal M25XP - "As We Wish" Bellingham, WA - San Juan Islands

KWKloeber

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Re: Shortening the drive shaft for new transmission
« Reply #18 on: July 18, 2022, 10:14:12 PM »

Remember that if you want to get wet you can stuff the outside of the log and control a great amount of flow that will come in around the shaft.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

kable

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Re: Shortening the drive shaft for new transmission
« Reply #19 on: July 21, 2022, 10:27:14 AM »

I called Federal Marine Transmission to ask some questions and order their flexible coupler.
https://federalmarinetransmissions.com/contact.html
708-352-2200 (Jim)

He was very knowledgable and provided a lot of history.
It ended up being part # 43A w/ 1" diameter. about $380
https://0201.nccdn.net/1_2/000/000/0d7/d2a/2022--federal-flexible-couplings.pdf
The part has to be 'made' which takes about a week.
No mention of a grounding strap.
He said to continue to use the existing old stiff coupler for initial transmission / shaft alignment, then re-install this flexible coupler.

Question/confirmation about the use of a key way.
I said I would be cutting off the front of my shaft and would likely be loosing the key way and that I had heard the key way was not required.  He was very adamant that the key way is still required.  I mentioned others had success w/ out the key way and he said the only thing he could think of is that they were using the set screws to tighten against the shaft and this wasn't correct.  ????
He said the shaft should be pulled, sent off w/ the coupler, re keyed and re-drilled for set screws and fit the new flex coupler to the shaft.  He said every shaft is different, like a fingerprint and could be off by a 1K of an inch, etc.

So, now my big concern is the key way.  @Ron Hill - I know you have had success, any thoughts?

Now my current thoughts are to get in there and get an exact measurement of my current hard coupler + drive saver.  This should be bigger (longer) than the new Federal flex coupler (2 11/16"???).  So how much bigger?  I need to find 1.5" for the longer transmission.  I am guessing I still need to shorten the shaft 1/2". 

If I need to pull the shaft and re-cut a key way, I have to for sure pull the boat, cut out the cutlas, pull the shaft back past the rudder, have the shaft properly cut down to account for the prop length behind the strut etc. Reapply bottom paint, etc. (did all this 2 years ago).

Maybe, for now, just simply push the shaft back the 1/2" (making the prop / strut distance worse), but maybe 'this' can be done safely in the water?  This would buy me another year (bottom paint, $, time).  So thoughts on experiences/safety of just pushing the shaft back a bit while in the water?  Or are all the risks the same?
« Last Edit: July 21, 2022, 10:29:27 AM by kable »
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1988 C34 #785 SR/WK Universal M25XP - "As We Wish" Bellingham, WA - San Juan Islands

KWKloeber

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Re: Shortening the drive shaft for new transmission
« Reply #20 on: July 21, 2022, 11:07:01 AM »

@kable

Itís just common sense that a keyís purpose it to transmit a certain torque of an axial load while being able to shear if there is a situation where there is possible damage (hit an obstruction.)  Setscrews are intended to hold a coupling, etc., on a shaft not withstand the axial load where thereís a key or spline (e.g., alternator pulley, crankshaft pulley, crankshaft output shaft, transmission output shaft, etc.)  Ask FMT if thatís no so.

Thatís not to say that setscrews donít hold AT ALL, or that they wouldnít work (temporary?) but itís not their purpose.

There are ways to remove the shaft but it takes logistics and careful orchestration.  For instance the log can be olugged internally or with a cap.  Youíll get wet (temporarily? But not sink the boat unless the operation goes south (hence the careful orchestration needed.)  itís a gamble that must be weighed.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Ron Hill

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Re: Shortening the drive shaft for new transmission
« Reply #21 on: July 21, 2022, 03:29:48 PM »

Kable : I dumped my Driver Saver long ago for a flexible coupling, you definitely don't need both!!!  A flexible coupling "clamps itself around a shaft" so there is no need for a key way!!

a few thoughts
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