Prop shaft droops

[zboss]

Folks,

I am trying to align my engine. I have a new cutlass bearing already installed. The prop only slightly wiggled (maybe 1/16" or less - its not barely noticeable) when I tested on the hard back in November. However, I am in the water now and I am in the process of replacing my transmission.

When I disconnected the coupling and moved the shaft back an inch I noticed that the shaft can now be moved up and down by about 1/4". Without touching the shaft it naturally sits slightly lower than my new transmission coupling (same model transmission) by about 3/16".

If I were to hold the shaft up 3/16" I can slide the bolts into the coupling and begin the alignment process. However... should I be doing this?

Is the proper thing to do to move/lower/align the engine to be vertically in line with the drooping shaft so the bolts can be directly inserted and then begin the alignment process? Maybe I should meet the shaft droop half way? The cutlass bearing is the only thing supporting the shaft when its not connected since we have a full keel.

Confused as I see nothing in the literature about this situation.

- z

[Boatyarddog]

Lift slightly up on the shaft, and slip it onto the coupler.
There should be a sweet spot where the shaft is in the middle line of both the cutlass and the shaft tube.
The packing box, or bellows, can interfere with this fit.
Tighten the packing box hose clamps to the tube,last.
Be sure the shaft isn't touching the packing box adjusting nut.
Turn the shaft 180, measure the 4 quarters of the coupler for a maximum of .003 thousands of an inch. Between the two faces, un bolted.
Turn 180 and re measure, you shouldn't be able to slide a .003 feeler gauge, into to the seam between the two, any place along the seam all around the coupler.
Be sure the coupler faces are clean, and not dented in the coupler faces.
After finding the alignment, bolt the engine mounts in place and tighten the stud nuts on the engine mounts and recheck the alignment.
It may move slightly, when tightened, compensate if needed.
Always, recheck after splashing the boat.
If it's been on the hard for awhile give it a few, 3 Days to adjust for the water. Before final alignment.
The shaft should run smooth under test, with NO wiggle ing of the bellows or packing box.
Then adjust the drip of the packing box, or compress the bellows on PSS, 3/4".


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[Cheechako]

How long is your shaft? (inside the boat) I've never had a packing gland that allows the shaft to drop that much (1/4") unless you shaft is real long... lower the engine to match it.
The shaft should center it self in the packing gland as well as the cutlass bearing. (again: unless overhanging a lot inside the boat)

[zboss]

Originally Posted by Boatyarddog

Lift slightly up on the shaft, and slip it onto the coupler.
There should be a sweet spot where the shaft is in the middle line of both the cutlass and the shaft tube.
The packing box, or bellows, can interfere with this fit.
Tighten the packing box hose clamps to the tube,last.
Be sure the shaft isn't touching the packing box adjusting nut.
Turn the shaft 180, measure the 4 quarters of the coupler for a maximum of .003 thousands of an inch. Between the two faces, un bolted.
Turn 180 and re measure, you shouldn't be able to slide a .003 feeler gauge, into to the seam between the two, any place along the seam all around the coupler.
Be sure the coupler faces are clean, and not dented in the coupler faces.
After finding the alignment, bolt the engine mounts in place and tighten the stud nuts on the engine mounts and recheck the alignment.
It may move slightly, when tightened, compensate if needed.
Always, recheck after splashing the boat.
If it's been on the hard for awhile give it a few, 3 Days to adjust for the water. Before final alignment.
The shaft should run smooth under test, with NO wiggle ing of the bellows or packing box.
Then adjust the drip of the packing box, or compress the bellows on PSS, 3/4".


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Thanks for getting back to me so quickly! So you are saying to bring the shaft coupler to the transmission coupler not the other way around?

I was able to find some info on Professional Boat Builder magazine that says I need to get the weight of the unsupported end of the shaft and lift it using a device so to counter balance the droop. That seems incredibly difficult thing to figure out since I have no idea who makes our shaft - its 27 years old!

[Cheechako]

Originally Posted by zboss

Thanks for getting back to me so quickly! So you are saying to bring the shaft coupler to the transmission coupler not the other way around?

I was able to find some info on Professional Boat Builder magazine that says I need to get the weight of the unsupported end of the shaft and lift it using a device so to counter balance the droop. That seems incredibly difficult thing to figure out since I have no idea who makes our shaft - its 27 years old!

Again... how much length inside the boat are we talking? If less than a foot or maybe even 18", move the motor down to the shaft. With the cutlass (if you haven't already worn it oval) and the stuffing box, the shaft is probably supported... what maybe 1 ft? You want that support system to basically be in the "Free state" no side loads.

[zboss]

The shaft is maybe 18 inches between the trans coupling side and the hull, with the packing gland in between.

[Dsanduril]

Is the packing gland rigidly mounted, or flexible hose mounted? If rigid then I wouldn't expect the shaft to drop and would vote for lowering the engine. On the other hand, if the packing gland is flexible hose (or bellows a la PSS) then I would fully expect the shaft to drop, and in that case you would need to make sure the shaft is centered in the stern tube (which can be tough to do if you're in the water).

Our shaft, for instance, only has two support points; the cutlass bearing and the transmission coupling. The PSS is very flexible, and would easily allow the shaft to drop an inch or more when it is disconnected from the transmission.

[zboss]

Its a rubber packing gland with the packing gland assembly. Looks like this:

http://www.angelfire.com/tn/santana5...2/packing2.jpg

[Cheechako]

Originally Posted by zboss

Its a rubber packing gland with the packing gland assembly. Looks like this:

http://www.angelfire.com/tn/santana5...2/packing2.jpg

Yeah.. most packing glands are near rigid to arm strength. Modern ones with bellows may differ. I would definitely lower the engine.

[Dsanduril]

Pretty much identical to ours, when you disconnect the shaft from the engine it will likely drop until supported on the bottom by the stern tube (to which the flexible hose is attached). You'll want to pick the shaft back up until it is centered in the stern tube. In the water you will have to eyeball/estimate, out of the water I would pull the hose from the stern tube, get the shaft centered, and then re-attach the gland/hose assembly.

[Edit] from Cheechako's comment - really depends on how long the piece of hose is. For ours, with about 4" of hose (before we changed to the PSS) the shaft would easily drop 1/2" or more. Either way, to me the key is you want the shaft centered in the stern tube (assuming the cutlass is actually aligned with the tube) [/Edit]

[zboss]

I start with a course alignment by lowering the engine to meet the shaft halfway. If the alignment isn't working I can always adjust it till the vibration goes away. In all likelihood, I'm betting I could not properly align it the way it is now. I'm thinking another haul out may be in order because the shaft is 27 years old and I'm thinking its safer to just replace it now rather than wait until it breaks.

All this may be moot however because the mounting bolts are pretty well rusted. I'm going to try some CorossionX and see if that works as well as they say it does. If not, some heat may be in order.

Its a catch 22... in order to see if the shaft is aligned in the tube correctly you need to be out of the water but in order to properly align the shaft you need to be in the water.

[Boatyarddog]

The alignment is useless if the engine mount stud adjusting nuts and stringer bolts won't loosen or remain tight when you retighten them, make sure that is ok first, soooo.. Much easier to do then.
Align the trans coupler to the shaft in the rough alignment, then finish with the final alignment to where you cannot slip a .003 feeler gauge in the coupler seam anywhere around the coupler seam.



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[Boatyarddog]

Packing gland hoses are thick walled and can cock the shaft one way or another, especially short shafts so be sure it's the last thing you retighten on the shaft tube, then adjust the packing gland for drip.


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[Boatyarddog]

Originally Posted by Dsanduril

Is the packing gland rigidly mounted, or flexible hose mounted? If rigid then I wouldn't expect the shaft to drop and would vote for lowering the engine. On the other hand, if the packing gland is flexible hose (or bellows a la PSS) then I would fully expect the shaft to drop, and in that case you would need to make sure the shaft is centered in the stern tube (which can be tough to do if you're in the water).

Our shaft, for instance, only has two support points; the cutlass bearing and the transmission coupling. The PSS is very flexible, and would easily allow the shaft to drop an inch or more when it is disconnected from the transmission.

For you, it's an advantage to temporarily use a block of wood with a V notch, propped under the shaft to support the shaft in the rough alignment or the same for long shafts or heavy shafts.


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[Boatyarddog]

Originally Posted by zboss

Thanks for getting back to me so quickly! So you are saying to bring the shaft coupler to the transmission coupler not the other way around?

I was able to find some info on Professional Boat Builder magazine that says I need to get the weight of the unsupported end of the shaft and lift it using a device so to counter balance the droop. That seems incredibly difficult thing to figure out since I have no idea who makes our shaft - its 27 years old!

Since the engine is bolted in place it's the only thing you can do.
When you unbolt the coupler you slide it back ,so when you replace it it's the reverse slide the shaft facing to the trans facing.
If the packing gland hose is binding loosen the cramps, and wiggle it free, then feel with a bump on the shaft up in the tube, and estimate the approx center of the inside of the tube, that is the rough alignment position, pull the shaft back up to the trans coupler and it should be very close to the centerline of both faces. If not you may have some rough alignment of the engine mounts to do.


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