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Old 29-05-2014, 14:06   #1
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Stuffing box wobble = shaft bent?

Hi all,
After putting in a new cutlass bearing and putting on a new prop on my old shaft this year I now have a very distinct wobble to my stuffing box. I rolled the shaft on a flat surface once I had the prop off and it looked ok but I didnt get out a dial gauge. Of course the boat is now in the water too. Last year while anchoring we wrapped the dinghy painter in the prop in reverse at idle and stalled the engine. The shaft size is only 3/4" on my Universal Atomic 4. The prop I put on is used but looked to be in perfect condition with no chips dents dings or pits, it literally looked brand new. I bought it from our local boat scrapping yard/ used parts seller.

What do you think, do you think its a bent shaft from wrapping the dinghy painter or is it a prop shaft/ engine alignment issue? Im interested hear you thoughts.

Also noone knows the length for a columbia 29 prop shaft do they? I know its a long shot and will vary if it has a different engine than it came with but worth a shot. If I can find that out I can put a new shaft in, in just a few hours in the hoist. Otherwise I'll be out of the water for a week or two.
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Old 29-05-2014, 14:11   #2
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Re: Stuffing box wobble = shaft bent?

Sounds like you need to align the engine with the drive shaft.

Inboard Engine Alignment - Frequently Asked Questions - eBasicPower.com
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Old 29-05-2014, 14:37   #3
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Re: Stuffing box wobble = shaft bent?

could be cuttlas bearing or alignment,or prop balance if shaft rolled true that is
all it could be. Is the water warm where you are ??? Ole
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Old 29-05-2014, 14:39   #4
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Re: Stuffing box wobble = shaft bent?

Take the prop off and have it checked to see if it's in balance or if the original prop isn't damaged put that back on and see what happens.

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Old 29-05-2014, 16:02   #5
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Re: Stuffing box wobble = shaft bent?

You used hose from a roll. Stuffing box hose comes in straight lengths. There is plenty of hose that looks like stuffing box hose but it's not. Even the slight curve from hose from a roll will cause the wobble you see. It won't ever come out either.
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Old 29-05-2014, 16:21   #6
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Re: Stuffing box wobble = shaft bent?

I didn't change the stuffing box hose. Besides even if it had a curve wouldn't the prop shaft if straight and true and the engine aligned hold the stuffing box in place? Thanks for the thoughts and ideas. Trying to align the engine tonight.
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Old 29-05-2014, 16:49   #7
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Re: Stuffing box wobble = shaft bent?

I would be more inclined to think that it is engine/transmission alignment. I'd mess with that before pulling the prop. Prop balance would also do it.
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Old 29-05-2014, 17:36   #8
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Re: Stuffing box wobble = shaft bent?

Hi, You might be dealing with Shaft Whip. A quick test is to remove the propeller and then run the engine and test for the wobble again. If its the same, the shaft is most likely bent. What happens is the prop blades are pushing with an unequal force, so lets assume one blade is pushing more than the others for the moment. That excess force on one side of the prop will tend to push the shaft (and the boat) forward in concert but, because it has more (or less) pitch than the others, it also tends to bend the shaft away from (or toward) itself especially in the middle of the longest unsupported length of shaft.

Does it get worse with more RPM and better at idle?
Can you mark the side of the shaft that is "high" with a sharpie pen in ahead by bringing the pen slowly toward the side of the shaft while it is "whipping", then Do the same in Reverse, if the marks stay on the same side, its the shaft, if it goes opposite, its the prop.

Good luck!
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Old 01-06-2014, 17:37   #9
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Re: Stuffing box wobble = shaft bent?

Just put the transmission in neutral with the engine off and manually turn the engine flange by hand while watching the stuff box and see if it moves. If it moves try and separate the engine flange from the shaft flange and using a feeler guage between the flanges see if there is more than 10 thousands of an inch top, bottom and side to side. If greater than that then loosen the engine mounting bolts and with a small pry, move the engine to proper alignment.
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Old 01-06-2014, 17:56   #10
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Re: Stuffing box wobble = shaft bent?

We would aim for 4 mil or better at the coupling flanges when aligning. Shaft runout can really only be checked on the bench with two v-blocks and a gauge. Catching a rope in the prop is unfortunately enough to bend a shaft. But...Something that causes a gross wobble at the stuffing box sounds more drastic, like the prop unbalance or alignment.

Good luck.
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Old 01-06-2014, 18:27   #11
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Re: Stuffing box wobble = shaft bent?

You have two variables at work, given the fact that you replaced the cutlass bearing and rolled the shaft and it appeared true and straight. What you're left with is 1) a prop of unknown symmetry and 2) fouling a line on the shaft. It begs the question of whether you observed any oscillation or vibration after your repairs but before your encounter with the fouled prop.

Makes sense to run the shaft without a prop on. If the problem goes away, then you likely bought a bent prop (and at 2000 rpm, a deviation in the prop that you can't see with the naked eye becomes a problem). If not, then you likely have a bent shaft or alignment issue. alignment is the easy thing to check so start with that, then remove the prop, and if that does not give you any joy you need to haul the boat and check the shaft again for trueness and your cutlass bearing again (when you pull the shaft, why not?)
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Old 01-06-2014, 21:47   #12
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Re: Stuffing box wobble = shaft bent?

First do a careful shaft alignment. If no joy, then send the shaft, coupling and prop for service.
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Old 02-06-2014, 01:02   #13
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Re: Stuffing box wobble = shaft bent?

I might just repeat what others have said with some of this but here goes anyway.
Since the last things you did was change the prop and put in a new cutlass bearing then knowing whether or not you had a wobble before you made those changes would be important. Was there a wobble before you hauled the boat?

Stalling the engine with a line wrap should not have bent your shaft. That's very unlikely. Having the engine come out of alignment because of a deteriorating engine mount is a possibility but knowing if your newly installed prop is balanced is important too.

I would check the things that you can while in the water before hauling out again to pull the shaft. If you or a diver can remove the prop easily then do that and take it to a prop shop and have it balanced. If you can uncouple the shaft from the trans easily and give it a spin test then do that. You can check to see if any of the bolts that you used to reinstall your prop shaft have been torqued properly. You'll want to realign your engine/trans before you bolt that back up. A simple test for engine mount failure is getting your hands on the engine and trying to shake it from side to side. If it feels sloppy then you have an engine mount problem.
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Old 02-06-2014, 07:15   #14
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Re: Stuffing box wobble = shaft bent?

While aligning your shaft and transmission couplings, take a look the the faces on flanges make sure they are smooth.
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Old 02-06-2014, 08:56   #15
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Re: Stuffing box wobble = shaft bent?

An alignment needs to be done anyways. If it cures the problem then that's an added bonus!
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