Last week, while singlehanding my Catalina 30 one night, the propeller fell off and was lost to the depths. How this happened will never be known for certain. It was an expensive feathering propeller that had been on the boat for 6 years. The tow back into my tight slip was also $$$$. Anyway, I hired a diver to put my original fixed-blade prop back on the boat. He discovered that the prop shaft had been cut down a bit as part of the installation for the feathering prop which I had lost. As a consequence, there were not enough threads on the shaft to install both the usual jam nut and locking nut. He could only fit the one, full-height nut, which he tells me he fully engaged on the shaft, torquing it down hard. No cotter pin could be placed, since that part of the shaft was gone. I have to make a 12 mile trip to get hauled out for the season, which is now over here in Chicago. While I can sail most of the way, the last mile and a half will be up a river that has very large barge traffic. Naturally, I'm concerned that my propeller stay attached! But I'm wondering if any of you have had your propeller similarly installed for some brief period of time, hopefully without problem. If so, should I motor at very low RPM's? Lock the shaft in gear while sailing? Any thoughts are appreciated.
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Maybe the shaft broke
The bronze shaft on my old Pearson broke when trying to remove the locking nut. Right between the 2 nuts so it only left enough threads for 1 nut. It happened very easily and with very little force. It must have had a crack because it was red and chalky. I had one custom made from SS. Take a close look at yours and make sure it really was cut. This could also explain the loss of the prop. Tim R.
The bronze shaft on my old Pearson broke when trying to remove the locking nut. Right between the 2 nuts so it only left enough threads for 1 nut. It happened very easily and with very little force. It must have had a crack because it was red and chalky. I had one custom made from SS. Take a close look at yours and make sure it really was cut. This could also explain the loss of the prop. Tim R.
There was a boat in our marina
two years ago that had lost the shaft up to the propeller hub. Discovered it when the boat was hauled for the winter. The prop stayed on ans he changed the shaft that winter. The prop should stay with you unless you back all the way.
two years ago that had lost the shaft up to the propeller hub. Discovered it when the boat was hauled for the winter. The prop stayed on ans he changed the shaft that winter. The prop should stay with you unless you back all the way.
In Theory
At least in theory, the sole purpose of the nut is to jam and lock the prop onto the shaft. The Morse taper is, IN THEORY, the total, and only necessary locking mechanism needed. Usually this holds, and you can take the nut off and not have a problem. I know it is hard to accept this idea, and can be worrisome. But you should have no problems, assuming that the prop seated onto the shaft as is should.
At least in theory, the sole purpose of the nut is to jam and lock the prop onto the shaft. The Morse taper is, IN THEORY, the total, and only necessary locking mechanism needed. Usually this holds, and you can take the nut off and not have a problem. I know it is hard to accept this idea, and can be worrisome. But you should have no problems, assuming that the prop seated onto the shaft as is should.
No keyway ????
When I read the post abt. the Morse taper I had to go & look at both my props , each of which have a square keyway milled in the hub. This corresponds to a keyway milled in the shaft. A Morse taper connection can transmit a fair amt. of torque (it's all that holds the chuck on my drill press) but I don't think it's able to hold a prop securely without a square key to back up the friction fit of the taper. I don't know if this is the case for all props but any that I've seen have a keyway in addition to the taper.
When I read the post abt. the Morse taper I had to go & look at both my props , each of which have a square keyway milled in the hub. This corresponds to a keyway milled in the shaft. A Morse taper connection can transmit a fair amt. of torque (it's all that holds the chuck on my drill press) but I don't think it's able to hold a prop securely without a square key to back up the friction fit of the taper. I don't know if this is the case for all props but any that I've seen have a keyway in addition to the taper.
Another suggestion....
While I realize this suggestion will cost the diver again, you could replace the standard nut with two jam nuts. The jam nuts are thinner and you could probably get two on the shaft. I suspect that the prop you lost was an Autostream since I know from my own installation that it is necessary to cut off the last nub on the shaft that contains the hole for the cotter pin. Am I right? I honestly think you will be just fine with the one nut.
While I realize this suggestion will cost the diver again, you could replace the standard nut with two jam nuts. The jam nuts are thinner and you could probably get two on the shaft. I suspect that the prop you lost was an Autostream since I know from my own installation that it is necessary to cut off the last nub on the shaft that contains the hole for the cotter pin. Am I right? I honestly think you will be just fine with the one nut.
It wasn't an Autostream, it was a J-prop
Rich, I think several of the feathering props require a trim of the prop shaft. This was a J-prop. The only warning was some increase in vibration the next to last time I went sailing. The night the prop fell off there wasn't any unusual vibration or noise. I had no idea the prop was gone until realized the boat wasn't moving when I engaged the engine. The suggestion about 2 jam nuts is one we have already considered. The diver put the half-height nut on first, then tried to see if he could engage some threads of the full-height nut as well, but he couldn't. He didn't think 2 jam nuts would fit on the shaft, but suggested I could try looking for a nut that was less than half-height and add that to the jam nut. The downside to that idea is that attempting to heavily torque a nut of that type might simply bend or twist it because of its reduced strength.
Rich, I think several of the feathering props require a trim of the prop shaft. This was a J-prop. The only warning was some increase in vibration the next to last time I went sailing. The night the prop fell off there wasn't any unusual vibration or noise. I had no idea the prop was gone until realized the boat wasn't moving when I engaged the engine. The suggestion about 2 jam nuts is one we have already considered. The diver put the half-height nut on first, then tried to see if he could engage some threads of the full-height nut as well, but he couldn't. He didn't think 2 jam nuts would fit on the shaft, but suggested I could try looking for a nut that was less than half-height and add that to the jam nut. The downside to that idea is that attempting to heavily torque a nut of that type might simply bend or twist it because of its reduced strength.
Morse taper and reverse gear
Nice n' Easy, The diver told me something similar to what you are saying. It makes sense to me, in that the propeller, when engaged in forward gear, should be driving itself forward on the shaft (by extremely tiny amounts). That's why a prop pulling device is often needed to remove a propeller that has been on for a while. As the prop moves that tiny extra bit up the shaft, it gets more firmly jammed on. Reverse gear would seem to be another matter, with the prop "trying" to drive itself aft on the shaft, as Ross seemed to be suggesting at the end of his post.
Nice n' Easy, The diver told me something similar to what you are saying. It makes sense to me, in that the propeller, when engaged in forward gear, should be driving itself forward on the shaft (by extremely tiny amounts). That's why a prop pulling device is often needed to remove a propeller that has been on for a while. As the prop moves that tiny extra bit up the shaft, it gets more firmly jammed on. Reverse gear would seem to be another matter, with the prop "trying" to drive itself aft on the shaft, as Ross seemed to be suggesting at the end of his post.
bob, where are you storing, skyway or crowleys
i would talk to the yard and have them at the ready if you need to be towed the last bit if you get stuck. i assume that you are going to replace the prop with the feathering prop? i too have a feathering prop and would not go back to the fixed. not only is there less drag but the motoring behavior is much better. good luck mike burnham harbor
i would talk to the yard and have them at the ready if you need to be towed the last bit if you get stuck. i assume that you are going to replace the prop with the feathering prop? i too have a feathering prop and would not go back to the fixed. not only is there less drag but the motoring behavior is much better. good luck mike burnham harbor
Replacing with folding prop -- probably
Mike, I'm storing at Crowley's. Thanks for the suggestion about having them stand by in case of trouble. In the last couple of days I came to the same conclusion. I would prefer to replace with a feathering propeller again, but I don't know if I can get myself to cough up the money. The J-Prop that I lost cost $1200 when I bought it 6 years ago. Because of the weakness of the dollar, it is now $1800. The Max-Prop may be a little less expensive, but you cannot easily adjust the pitch in the water. I'm trying to get prices for the other manufacturers (looking for a 2-blade). I may end up with a folding propeller such as a Martec or a Flex-O-Fold. The cost would be less, about $700-900. The biggest disadvantage is performance in reverse, although Martec claims their prop will crash stop a boat travelling at 5 knots in one and one-half boat lengths. As you know, a feathering prop can probably do a little better than even that.
Mike, I'm storing at Crowley's. Thanks for the suggestion about having them stand by in case of trouble. In the last couple of days I came to the same conclusion. I would prefer to replace with a feathering propeller again, but I don't know if I can get myself to cough up the money. The J-Prop that I lost cost $1200 when I bought it 6 years ago. Because of the weakness of the dollar, it is now $1800. The Max-Prop may be a little less expensive, but you cannot easily adjust the pitch in the water. I'm trying to get prices for the other manufacturers (looking for a 2-blade). I may end up with a folding propeller such as a Martec or a Flex-O-Fold. The cost would be less, about $700-900. The biggest disadvantage is performance in reverse, although Martec claims their prop will crash stop a boat travelling at 5 knots in one and one-half boat lengths. As you know, a feathering prop can probably do a little better than even that.
just a comment
I tried the same thing last month. drove about a mile then back to the slip. lost the prop in the last 100 yards.. ' I would not do it that way. sail it up and leave it in neutral. the problem as i see it is if the prop is driven up the shaft only slightly the nut is then loose. it will come off then the prop is ok only if in forward. if you drop it in neutral it may just come off. I think thats what cost me about 500 bucks. So if you sail it all the way. and tow it in you would be better off. unless you just want to have an excuse to by a new one. im suprised any prop would not need a cotter key to keep everything in place. maybe its time to re shaft and put a prop on theat locks in place.
I tried the same thing last month. drove about a mile then back to the slip. lost the prop in the last 100 yards.. ' I would not do it that way. sail it up and leave it in neutral. the problem as i see it is if the prop is driven up the shaft only slightly the nut is then loose. it will come off then the prop is ok only if in forward. if you drop it in neutral it may just come off. I think thats what cost me about 500 bucks. So if you sail it all the way. and tow it in you would be better off. unless you just want to have an excuse to by a new one. im suprised any prop would not need a cotter key to keep everything in place. maybe its time to re shaft and put a prop on theat locks in place.
Sailing in neutral will spin the prop forward
Ed, Sailing the 12 miles in neutral will leave the prop spinning as if it were driving the boat forward -- because the twist on a fixed blade is for forward thrust. So I'm not sure that would be a good answer. I would appreciate more details on your experience. How recently had the single nut been torqued onto the shaft? Did you have any warning before the prop was lost? Anything you can tell me will be helpful.
Ed, Sailing the 12 miles in neutral will leave the prop spinning as if it were driving the boat forward -- because the twist on a fixed blade is for forward thrust. So I'm not sure that would be a good answer. I would appreciate more details on your experience. How recently had the single nut been torqued onto the shaft? Did you have any warning before the prop was lost? Anything you can tell me will be helpful.
Prop drag
Bob, you are assuming that the spinning prop, if in neutral, will create forward thrust on the shaft. Think about this for a sec. It takes some effort to spin the prop. There will be some drag, to the rear, even if in neutral, but less than if you have the transmission in gear. With the tranny in gear, you will have quite a bit of drag. As you only have a short distance to go, and are worried about losing the prop on route, I would just motor the 12 miles. With the prop thrust on the shaft from motoring, I would think you should be fine. I wouldn't try backing down hard on it, but enough to get into a slip should pose no problem. If the diver got the nut good and tight, you should be able to back into the slip with no problem.
Bob, you are assuming that the spinning prop, if in neutral, will create forward thrust on the shaft. Think about this for a sec. It takes some effort to spin the prop. There will be some drag, to the rear, even if in neutral, but less than if you have the transmission in gear. With the tranny in gear, you will have quite a bit of drag. As you only have a short distance to go, and are worried about losing the prop on route, I would just motor the 12 miles. With the prop thrust on the shaft from motoring, I would think you should be fine. I wouldn't try backing down hard on it, but enough to get into a slip should pose no problem. If the diver got the nut good and tight, you should be able to back into the slip with no problem.
Makes perfect sense
Nice n' Easy, This makes perfect sense to me. Thanks! By the way, how is it that you are so knowledgeable about the Morse taper? I knew the shaft was tapered, but had never heard this particular term. Naturally, I Googled it!
Nice n' Easy, This makes perfect sense to me. Thanks! By the way, how is it that you are so knowledgeable about the Morse taper? I knew the shaft was tapered, but had never heard this particular term. Naturally, I Googled it!
Lots of different types of tapers in a shop
Lots of different types of tapers in a machine shop. The Morse taper is used on machine tools and drill bits and the Jacobs taper is used a lot on drill chucks. You also have the Brown & Sharp taper and the Jarno taper along with the SAE taper. As far as I know the standard taper for propeller shafts in the US is SAE taper and that’s about 3/4”” per foot while the Morse taper is about 5/8” per foot. A metric shaft has a metric taper. None of this matters in practice because it’s standardized and a propeller will mate with a shaft as long as a real machine shop makes everything. If you can only use one nut the best thing is to use locktight but for that you need to have the boat hauled. Failing that I would drill the nut off center (bronze nut) and use safety locking wire to make the trip. I would not run with just one nut unless the propeller, like some feathering ones had a locking system for the nut. The Martec for instance uses a special nut with a set of holes that line up with the propeller body hole. Good luck and all the best, Robert Gainer.
Lots of different types of tapers in a machine shop. The Morse taper is used on machine tools and drill bits and the Jacobs taper is used a lot on drill chucks. You also have the Brown & Sharp taper and the Jarno taper along with the SAE taper. As far as I know the standard taper for propeller shafts in the US is SAE taper and that’s about 3/4”” per foot while the Morse taper is about 5/8” per foot. A metric shaft has a metric taper. None of this matters in practice because it’s standardized and a propeller will mate with a shaft as long as a real machine shop makes everything. If you can only use one nut the best thing is to use locktight but for that you need to have the boat hauled. Failing that I would drill the nut off center (bronze nut) and use safety locking wire to make the trip. I would not run with just one nut unless the propeller, like some feathering ones had a locking system for the nut. The Martec for instance uses a special nut with a set of holes that line up with the propeller body hole. Good luck and all the best, Robert Gainer.
A bit more information, please
Robert, Could you please explain the use of locking wire in a bit more detail? Thanks very much. The Flex-O-Fold propeller can supposedly be installed with the boat in the water. Do you know if that is true of the Martec as well? Do either of these propellers require me to have an unaltered prop shaft?
Robert, Could you please explain the use of locking wire in a bit more detail? Thanks very much. The Flex-O-Fold propeller can supposedly be installed with the boat in the water. Do you know if that is true of the Martec as well? Do either of these propellers require me to have an unaltered prop shaft?
Nylon insert locking nut
I spoke to some specialists in a marine propulsion shop. Their recommendation is to replace the current full-height nut with a nylon-insert locking nut. If there is enough room, they also recommend using a bevel/compression/spring washer between the prop hub and the nut. This makes sense, and I'll likely be calling the diver to make the change. One other possibility was to "ding" the shaft to discourge the nut from backing off.
I spoke to some specialists in a marine propulsion shop. Their recommendation is to replace the current full-height nut with a nylon-insert locking nut. If there is enough room, they also recommend using a bevel/compression/spring washer between the prop hub and the nut. This makes sense, and I'll likely be calling the diver to make the change. One other possibility was to "ding" the shaft to discourge the nut from backing off.
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