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Discussion Starter #1
So, I almost sank my boat yesterday. I was doing some work on my engine and wanted to test it out. While still tied to the dock, I put it in forward and then reverse. As I was throttling up in reverse all of a sudden the RPMs spiked. I thought I had done something to the transmission but then my bilge pump came on. I looked down below and sure enough, I had a 1" stream of water shooting into my boat. The prop shaft had shot out the back. I had the leak plugged within a minute so no harm was done. I don't know if the set screw backed out or if the set screw wasn't properly in the dimple. Anyway, I have the shaft back in, the set screw is in the dimple and wired to the other one. Even though it is set up properly I am still paranoid. I know that some boats have a safety collar to prevent the shaft from coming out but this boat doesn't have one. What have other people done? I am wondering about drilling a small hole in the shaft and putting a pin or bolt through it. Something that would be set up so it could pull free from the engine but be stopped at the packing nut. My motor only puts out about 15-20 HP so the shaft is way overkill and I don't think a small hole would compromise the integrity enough to be a concern. Thoughts?
 

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One of None
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a split collar that tightens around the shaft with set screws
Good save!
McMaster-Carr
 

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I'd go with Denise's response, drilling 1 inch of stainless is a tad bit difficult with most hand drills
Even if the collar doesn't stop the shaft you'll hear the thunk as it hits bearing.
 

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I do two things. I position my zinc just forward of the strut so it will prevent the shaft from backing out in reverse. Secondly I have a stainless hose clamp on the shaft just forward of the packing gland. Both cheap and easy insurance.
 

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Discussion Starter #5
Thanks for the replies. I think I will add the hose clamp now and order a clamp on collar. That will give me a lot more piece of mine and confidence next time I put it in reverse.
 

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So, I almost sank my boat yesterday. I was doing some work on my engine and wanted to test it out. While still tied to the dock, I put it in forward and then reverse. As I was throttling up in reverse all of a sudden the RPMs spiked. I thought I had done something to the transmission but then my bilge pump came on. I looked down below and sure enough, I had a 1" stream of water shooting into my boat. The prop shaft had shot out the back. I had the leak plugged within a minute so no harm was done. I don't know if the set screw backed out or if the set screw wasn't properly in the dimple. Anyway, I have the shaft back in, the set screw is in the dimple and wired to the other one. Even though it is set up properly I am still paranoid. I know that some boats have a safety collar to prevent the shaft from coming out but this boat doesn't have one. What have other people done? I am wondering about drilling a small hole in the shaft and putting a pin or bolt through it. Something that would be set up so it could pull free from the engine but be stopped at the packing nut. My motor only puts out about 15-20 HP so the shaft is way overkill and I don't think a small hole would compromise the integrity enough to be a concern. Thoughts?


^ This is why I harp on PROPER fitting of the coupling to the shaft!!!! The set screws are not there to hold the coupling in place they are there, in addition to a properly fit shaft coupling....

Simply put you should not just be able to "slide" your shaft into the coupling. If you can, BAD FIT....
 

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Closet Powerboater
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For those with dripless packing, I've heard of people sliding the old fitting forward, and leaving it on the shaft so that if the old one fails, it can be slid back into place.

Anyone hear of this?

MedSailor
 

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For those with dripless packing, I've heard of people sliding the old fitting forward, and leaving it on the shaft so that if the old one fails, it can be slid back into place.

Anyone hear of this?

MedSailor
The fitting you refer to is the stainless steel "puck". A shaft with a dripless packing on it will never leave the boat. The bellows may fail and you'll fill up with water that way (whole different process for stopping the flooding). In addition to that I install a hose clamp directly fwd of the "puck" to keep the proper tension on the bellows and the carbon fiber face.
 

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Closet Powerboater
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I think the Puck is a standard part of the kit right? Some units were famous for having double set screws that caused it to fall out. Are we talking about the same part?

What I heard was definitely leaving the entire bellows assembly on the shaft so that it could be slid aft once the old failed one was cut away. Sounds like a good armchair theory to me, but I'm having a hard time imagining how you could "easily" slide it on on after removing a messed up, failed unit.

MedSailor
 

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I think the Puck is a standard part of the kit right? Some units were famous for having double set screws that caused it to fall out. Are we talking about the same part?

What I heard was definitely leaving the entire bellows assembly on the shaft so that it could be slid aft once the old failed one was cut away. Sounds like a good armchair theory to me, but I'm having a hard time imagining how you could "easily" slide it on on after removing a messed up, failed unit.

MedSailor
Exactly correct. The puck has set screws. If those set screws loosen up the puck can wiggle fwd, opening up the gap between the puck and the carbon fiber face (which is clamped into the bellows) allowing water in. Mine was dripping water and I saw that all the tension was gone. Then I discovered it was 11 years old! YIKES! They're factory recommended for no more than 5 years.

Your also correct about being a bear to change. The emergency procedures are to have a piece of innertube type material to stretch and wrap around the failed bellows and zip tie in place. There is a "quick change" type of kit out there, but that's still to be done out of the water, and is for ease of maintenance, not damage control while under way.

The hose clamp I put on the shaft fwd of the puck is to keep it in place should the set screws not do their job.
 

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A firend of mine had his prop shaft slide off the coupling flange while sailing. Lucky for him it was stopped by his rudder. I suppose not all boats has prop shaft longer than space between prop & rudder.
JimsCAL mentioned having the zinc double as stopper forward of the strut ...I think that's a good idea. :)
 

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Set screws are only good for one use as the get "blunt" - they should be replaced if they are backed out.
I think he was talking about the coupling set screws which SHOULD fit into spottings in the shaft. Still his coupling fit is WRONG and it should NOT rely on the set screws even if the shaft is spotted... Someone probably removed,it, never checked the fit, and reinstalled it..

PSS set screws are a ONE TIME tighten... Even if you snug and then decide you need to readjust you then need NEW set screws. The shaft is much harder than the 18/8 SS set screws so new ones every time you adjust.....
 

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Discussion Starter #18
Thanks for the tip on the set screws. I will be installing the collar this weekend so I will get new set screws too. The shaft does not have a significant amount of play. It took a couple light taps to get it all the way in. I just think either the set screw backed out or it wasn't in the dimple to begin with.
 

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HANUMAN
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Are these set screws sold in hardware stores or are they special order. I have a small leak only under power and would like to inspect the collar face and and clean it. Is there a technical term besides "set screw"?
 

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One of None
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Are these set screws sold in hardware stores or are they special order. I have a small leak only under power and would like to inspect the collar face and and clean it. Is there a technical term besides "set screw"?
Rob, to clean the collar one just need pull back on the bellows and the water pressure washes the face of the collar/s I had to do it a couple of times when we installed it (about 5 years now) One time a wiped the face with a finger tip wrapped in cloth. Be sure your bilge pump is working first!
 
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