Well it finally happened, we sucked up the dinghy painter while backing down on the anchor. The good news is that it wrapped neatly around the shaft in the 2" between the prop and the cutlass bearing and came off with only 3 breaths of air. It did stop the engine and sank the dink. The bad news is that now the propulsion combination vibrates and knocks badly at about 1500 RPMS and anything over 2500. I guess there are 3 possiblities: 1- bent shaft (bronze) 2- bent prop (2 blade) 3- bent strut and mis-alligned engine Anyone had this problem? Any way to check without hauling out? I've already got a call into the mechanic but I really hate having to do that if I can avoid it.
engine/shaft vibration & noise
- Thread starter Timbo3
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Not likely....
That 1 2 or 3 occurred unless you were doing 25 mph in reverse. You yourself can check the prop by diving once more and feeling for knicks or bends. A competent mechanic can reallign fairly quickly in the water by using a laser gun directed to a reflector he attaches on the fan belt wheel. No biggie and you'll be back in biz. I gave up the dinghy after dropping the engine in the water -- twice.
That 1 2 or 3 occurred unless you were doing 25 mph in reverse. You yourself can check the prop by diving once more and feeling for knicks or bends. A competent mechanic can reallign fairly quickly in the water by using a laser gun directed to a reflector he attaches on the fan belt wheel. No biggie and you'll be back in biz. I gave up the dinghy after dropping the engine in the water -- twice.
You can check for a bent blade with a stick and a pencil
You would need a stick about the size fo a paint stirring paddle The end goes against a strut or some other fixed point turn the prop so taht the first blade is pointed straight up and measure and mark your stick put the next blade in position and mark that one. Go back to the surface and compare your marks.
You would need a stick about the size fo a paint stirring paddle The end goes against a strut or some other fixed point turn the prop so taht the first blade is pointed straight up and measure and mark your stick put the next blade in position and mark that one. Go back to the surface and compare your marks.
doesn't help you now....but maybe for next time
http://shop.sailboatowners.com/detail.htm?fno=400&group=609
http://shop.sailboatowners.com/detail.htm?fno=400&group=609
Me Too
But I didn't run over anything, first sail of the season and something just didn't feel or sound right and then all of a sudden no propulsion. Engine kept running, driveshaft kept turning, but it wasn't turning the prop. The driveshaft can move fore and aft about an inch, it feels like it can reset itself when pushed aft but something is wrong in the stuffing box, cutlass bearing or something to allow this movement. I took a dive after docking and the prop is still there. Would it be possible me to see if anything can be done without hauling her out? I know I am a wishful thinker.
But I didn't run over anything, first sail of the season and something just didn't feel or sound right and then all of a sudden no propulsion. Engine kept running, driveshaft kept turning, but it wasn't turning the prop. The driveshaft can move fore and aft about an inch, it feels like it can reset itself when pushed aft but something is wrong in the stuffing box, cutlass bearing or something to allow this movement. I took a dive after docking and the prop is still there. Would it be possible me to see if anything can be done without hauling her out? I know I am a wishful thinker.
I, repeat I, not my crew, did just that in Dec. 1998
six months after getting our new to us boat. It runs better now...
Really, check all three out, whaddaya got to loose? We did. The "better," but much longer stories, have to do wtih how we got them OFF!
six months after getting our new to us boat. It runs better now...
Really, check all three out, whaddaya got to loose? We did. The "better," but much longer stories, have to do wtih how we got them OFF! 
Also..
As others have said check all three but I'll add one more. Check your motor mounts. A wrap tight enough to stall a diesel engine can be enough to also break an older motor mount which would certainly throw the alignment off. My honest guess is that it's alignment or a motor mount. I've wrapped LOTS of stray floating line and quite a few lobster pots over the years and never once bent the shaft or prop while doing so and I'm usually at full cruise RPM when this happens. Of course anything is possible, and you could have bent the shaft or prop, but start with what you can eliminate while in the water and that is alignment and motor mounts.
As others have said check all three but I'll add one more. Check your motor mounts. A wrap tight enough to stall a diesel engine can be enough to also break an older motor mount which would certainly throw the alignment off. My honest guess is that it's alignment or a motor mount. I've wrapped LOTS of stray floating line and quite a few lobster pots over the years and never once bent the shaft or prop while doing so and I'm usually at full cruise RPM when this happens. Of course anything is possible, and you could have bent the shaft or prop, but start with what you can eliminate while in the water and that is alignment and motor mounts.
Barnacles ?
Perhaps some barnacles got scrapped off but rather unevenly. When my stern gear vibrates, I know I have barnacles. Dove under, clean up and it vibrate no more.
Perhaps some barnacles got scrapped off but rather unevenly. When my stern gear vibrates, I know I have barnacles. Dove under, clean up and it vibrate no more.
Its easy to knock a shaft out of alignment and make it 'out of round'
Bar used to make shaft is inherently unstable and easily 'stress relieves' into a bent shaft by errant side loads applied. For shaft whip and vibration problems its always best to start with the shaft and see if its still running 'true'. A shaft with a small amount of bend (runout) is easily corrected by a machinist .... who probably straightened the shaft to 'true' when it was made. To check the shaft for 'true', apply a surface gage (micrometer with a small cam arm/lever) in several places, turn the shaft and check for 'runout'. Easy to fix if the shaft has noticeable (but large amount of) 'runout' by a machinist. Its easy to bend a shaft. Shaft 'runout' can easily change the 'natural frequency' of a shaft and cause violent vibrations when the shaft is running at the same speed of its 'natural frequency'.
Bar used to make shaft is inherently unstable and easily 'stress relieves' into a bent shaft by errant side loads applied. For shaft whip and vibration problems its always best to start with the shaft and see if its still running 'true'. A shaft with a small amount of bend (runout) is easily corrected by a machinist .... who probably straightened the shaft to 'true' when it was made. To check the shaft for 'true', apply a surface gage (micrometer with a small cam arm/lever) in several places, turn the shaft and check for 'runout'. Easy to fix if the shaft has noticeable (but large amount of) 'runout' by a machinist. Its easy to bend a shaft. Shaft 'runout' can easily change the 'natural frequency' of a shaft and cause violent vibrations when the shaft is running at the same speed of its 'natural frequency'.
And...
You are long way from hauling the boat. First - and easiest to check right now is the engine alignment. First, just look things over - check for a broken mount like Mainesail suggest. Grab your engine and see if you can make it slide a little on its mounts, perhaps your mount bolts have become a little loose. Fouling your prop would definitely cause the engine to shift if it was not tight on the mounts. Next, start your engine and put it in gear and observe it and your shaft while it is running. You may be able to see the problem right there. Next, disconnect the shaft from the trans at the flange (stop engine first!). DO NOT remove the flange from the shaft. The flange is in two halves - one connected to the shaft and the other to the trans. You just want to get the two halves spread apart an eight of an inch or less so you can insert a feeler gauge in there to be sure that the two flange faces are the same distance apart all around the circumference of the flange faces. If the faces are within .001 for every inch of flange diameter this is probably not the problem as that is OK. Alignment is adjusted by loosing the motor mounts and shifting the engine by hand in very small increments. Mounts can adjust up and down as well. Make very small changes and recheck with the feeler gauge often until you get it. Tighten down mounts and use the bolts in the flange to pull the two halves back together. Be sure to tighten each bolt only a turn at a time and evenly jumping from one edge of the flange to the opposite as you go. This procedure is not that difficult for anyone with a little mechanical ability. The tough part may be that the flange has frozen to its partner - not uncommon - and this can be very hard to free up and end up being more than you want to get into. My bet is on alignment. I have never heard of anyone bending a shaft in this manner - though I suppose it is possible. Again I recommend Don Casey's "This Old Boat" to step you through the alignment.
You are long way from hauling the boat. First - and easiest to check right now is the engine alignment. First, just look things over - check for a broken mount like Mainesail suggest. Grab your engine and see if you can make it slide a little on its mounts, perhaps your mount bolts have become a little loose. Fouling your prop would definitely cause the engine to shift if it was not tight on the mounts. Next, start your engine and put it in gear and observe it and your shaft while it is running. You may be able to see the problem right there. Next, disconnect the shaft from the trans at the flange (stop engine first!). DO NOT remove the flange from the shaft. The flange is in two halves - one connected to the shaft and the other to the trans. You just want to get the two halves spread apart an eight of an inch or less so you can insert a feeler gauge in there to be sure that the two flange faces are the same distance apart all around the circumference of the flange faces. If the faces are within .001 for every inch of flange diameter this is probably not the problem as that is OK. Alignment is adjusted by loosing the motor mounts and shifting the engine by hand in very small increments. Mounts can adjust up and down as well. Make very small changes and recheck with the feeler gauge often until you get it. Tighten down mounts and use the bolts in the flange to pull the two halves back together. Be sure to tighten each bolt only a turn at a time and evenly jumping from one edge of the flange to the opposite as you go. This procedure is not that difficult for anyone with a little mechanical ability. The tough part may be that the flange has frozen to its partner - not uncommon - and this can be very hard to free up and end up being more than you want to get into. My bet is on alignment. I have never heard of anyone bending a shaft in this manner - though I suppose it is possible. Again I recommend Don Casey's "This Old Boat" to step you through the alignment.
Bet its a bent shaft
I hit something in the water a few years back. It bent the prop and also the bronze shaft. Replaced the bronze shaft with stainless Steel as it has less problems with bending. If i were a betting man, i would say its the shaft.
I hit something in the water a few years back. It bent the prop and also the bronze shaft. Replaced the bronze shaft with stainless Steel as it has less problems with bending. If i were a betting man, i would say its the shaft.
I doubt that a propeller shaft is as easily bent as a rifle barrel
My 3/4 inch shaft is unsupported for about 6 inches aft of the cutlass bearing. I am quite certain that that length of shaft would do structrual damage to the boat before it would bend. We don't know the diameter of the prop shaft here but give a thought to the strength of metal.
My 3/4 inch shaft is unsupported for about 6 inches aft of the cutlass bearing. I am quite certain that that length of shaft would do structrual damage to the boat before it would bend. We don't know the diameter of the prop shaft here but give a thought to the strength of metal.
The problem turns out to be a bent shaft. . .
and the cutlass bearing got damaged too. I paid a diver cleaning my neighbor's boat a beer and a few bucks to check it out last night and he confirmed it is a bent shaft (1" bronze) and it's taken a chunk of rubber out of the cutlass bearing. The good news is that his company can replace the shaft and cutlass bearing with the boat in the water. I'm going to replace the bronze with stainless so this won't happen so easily again. They'll also replace the shaft log while it's convenient, cutlass bearing, zinc, & packing. I wish I knew about these guys last year since I paid an arm and a let to haul out just for a cutlass bearing. . . yes 2 in 13 months :-( I'm also going to replace the painter with a rope that floats or put floats on it. It only takes one time. I wonder what the recycle center pays for bronze - guess I'll find out. Thanks for the input folks, and I'm very glad to know how to align the engine. - Tim
and the cutlass bearing got damaged too. I paid a diver cleaning my neighbor's boat a beer and a few bucks to check it out last night and he confirmed it is a bent shaft (1" bronze) and it's taken a chunk of rubber out of the cutlass bearing. The good news is that his company can replace the shaft and cutlass bearing with the boat in the water. I'm going to replace the bronze with stainless so this won't happen so easily again. They'll also replace the shaft log while it's convenient, cutlass bearing, zinc, & packing. I wish I knew about these guys last year since I paid an arm and a let to haul out just for a cutlass bearing. . . yes 2 in 13 months :-( I'm also going to replace the painter with a rope that floats or put floats on it. It only takes one time. I wonder what the recycle center pays for bronze - guess I'll find out. Thanks for the input folks, and I'm very glad to know how to align the engine. - Tim
tim! i learned the hard way!
a poly painter can also be sucked into the prop when backing down to set the anchor. i learned with one short lesson to pull the painter in close before backing down. man was that water cold off sandy hook on memorial day weekend. family jewels still scream at the thought of it. s/v Que Pasa?
a poly painter can also be sucked into the prop when backing down to set the anchor. i learned with one short lesson to pull the painter in close before backing down. man was that water cold off sandy hook on memorial day weekend. family jewels still scream at the thought of it. s/v Que Pasa?
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