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Old 18-12-2014, 13:00   #1
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Cutlass Bearing on Prop Shaft Stops Motor

I have a problem that I hope someone has seen before:

Prop shaft tightens up after a short period in gear; to the point that it stalls the motor due to the friction.

I have an old fiberglass boat that hasn't been hauled out in years - now, I do plan to haul out beginning of 2015. So, yes that is the obvious solution.

But in the mean time...

Does anyone know what causes this?

I have changed the packing already. I have let it sit for a couple days after changing the packing and will try again today to run it in gear.

The only other detail is because it sat in the water for so long the diver had to muscle the prop loose just to get it to spin.

I'm having trouble finding pictures of cutlass bearings and such online that look like a match, so I'm giving the forum a swing at it.

Here's a pic of the hardware. I'll be cutting this shaft off the yolk in January when I haul out, R&R the thruhull, and hopefully not replacing the whole shaft...we'll see when I get there.
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Old 18-12-2014, 13:15   #2
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Re: Cutlass Bearing on Prop Shaft Stops Motor

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Originally Posted by Marpessa View Post
I'll try this again with pic
No pic so far. Keep trying.
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Old 18-12-2014, 13:19   #3
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Re: Cutlass Bearing on Prop Shaft Stops Motor

How much are you tightening the packing? Are you getting a slow drip, drip, drip from the packing gland when the shaft isn't turning? What about when it is turning? You should be getting a few drips when it's turning. If you aren't then you may have the packing tightened too much and when the shaft starts turning the packing heats up and works like a brake.

How warm are the nuts and body of the stuffing box when the engine bogs down? Should be just warm and comfortable to the touch. If it's hot then again, probably too tight.
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Old 18-12-2014, 13:21   #4
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Now I got it. Confusing website...VIDEO not attachment dummy
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Old 18-12-2014, 13:24   #5
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Heat is not an issue and there's plenty of water. I haven't been able to run long enough in gear at a high rate of RPM to get any heat at all at the bearing/shaft It starts to load up the drive train pretty quickly. Reverse same problem.
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Old 18-12-2014, 13:56   #6
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Re: Cutlass Bearing on Prop Shaft Stops Motor

When you replaced the packing did you replace single pieces that make only one wrap around shaft. Takes multiple single wraps.

Or did you use a long piece and make many wraps. If you did this, the packing will tighten up and lock the shaft. Don't ask me how I know this!!!http://www.cruisersforum.com/images/...s/banghead.gif
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Old 18-12-2014, 14:12   #7
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Luckily my engine is only 27hp, I've heard what can happen with a 4 cyl...

Yes I looked at youtube and learned how to install. It's done correctly, three separate cuts, all seams offset by 120* using the graphite strand stuff.

I guess the only thing I didn't do is use any lube, but the youtube video didn't use it on the graphite strand and only the flax instructions called for it... so I guess I skipped that step (technically).
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Old 18-12-2014, 14:14   #8
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Are you sure the problem is with the packing gland and not something else like the transmission? Any chance something is fouled around the prop or inside the shaft log?

So when the shaft locks up is it a slow process or all of a sudden? Is there still water dripping out of the packing when the shaft stops?

Seems odd that the packing could lock up the engine and not get warm at all. It would take a pretty good bit of friction for the packing to be the cause. If you wrapped the packing in one long strip like Gypsydfj mentions that might stop the shaft without getting it hot but I think the shaft would stay locked up and not start turning again after sitting for while.
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Old 18-12-2014, 14:18   #9
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Re: Cutlass Bearing on Prop Shaft Stops Motor

If the drive behaved in the same way before and after recaulking the stuffing box then:
The old caulking was not entirely removed and is still jamming
It is another component such as the rear bearing in the gearbox that' s jamming. If the oil seal is worn and water gets in, the ball bearing will rust and overheat when operated. This will lead to jamming. Maybe your gearbox oil level is low and the back bearing is not getting lubricsted.
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Old 18-12-2014, 14:27   #10
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Diver says it looks good but I'll have him by again to watch it spin in the water under load. I can't guarantee that the trans is good but there's no indication otherwise. Fluid has been changed and all.
I don't think it's the transmission because I can shift it back into gear or reverse later and it runs again...but it really is impossible to say until I remove all possible failures at the bearing/thruhull.

That's what's so weird about the whole situation - and nobody has seen this before...

I can run it at low RPM but I don't want to damage the shaft if something is making contact in the thruhull.

Everybody says it's just rubber, but I really have no idea what's truly in there.

I CAN do damage there, RIGHT? I'm assuming the answer is yes.

Here's what I'll do: I'll try again today. If it hasn't worked itself out then I'll get the diver in the water, run it until it locks up and stalls, then have diver shake the prop and try to locate where it's binding.
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Old 18-12-2014, 14:32   #11
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Re: Cutlass Bearing on Prop Shaft Stops Motor

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So when the shaft locks up is it a slow process or all of a sudden? Is there still water dripping out of the packing when the shaft stops?
It will run for a couple minutes, 1:30 or so, then you can hear the motor load up and the shaft kinda seems to vibrate more, and if you crank up rpms it will really vibrate and stall motor.

If you just leave at the rpm level when you hear it start to struggle and load up it will just kill the motor pretty quick, but when you hear it load up and shift into neutral real quick you can save it from stalling...

I hope that explains it as to your Question
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Old 18-12-2014, 17:51   #12
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Re: Cutlass Bearing on Prop Shaft Stops Motor

I would not turn it again under any circumstance, I'd have the boat pulled and find out what is going on, I just can't imagine this working itself out.
But then I guess I'm over cautious
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Old 18-12-2014, 17:53   #13
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Broken engine mount, engine way out of alignment? Just purely a WAG
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Old 18-12-2014, 17:54   #14
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Re: Cutlass Bearing on Prop Shaft Stops Motor

Perhaps you picked up some monofilament or something on the OUTSIDE?

If it's jammed in tight it might be hard to see?

What does it do in reverse?
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Old 18-12-2014, 18:01   #15
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Re: Cutlass Bearing on Prop Shaft Stops Motor

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I would not turn it again under any circumstance, I'd have the boat pulled and find out what is going on, I just can't imagine this working itself out.
But then I guess I'm over cautious
I agree.... You stand a good chance of doing some serious damage to power train.

Prior to haulout.. ...I would decouple shaft from reduction gear and dock trial engine and gear in Fwd/Reverse to make sure that the problem is not internal or fuel related
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