Okay, here I go again. After reading about shaft vibration on a Yanmar web site it mentioned my exact problem. My shaft vibrates against the stern tube at certain RPM's. This became more acute after the I had the engine mounts replaced and a PSS dripless shaft seal installed. Myself followed by two competent mechanics worked on the shaft alignment and managed to get it minimized. My question is about replacing the stern tube with a slightly larger one as the Yanmar web site suggests. Has anyone ever done this with a H33? I'm wondering about whether or not there is enough glass around the stern tube to do this without making the area too weak and flimsy. We are only talking about increasing the tube size up to a 1/4" more. I would only consider this if I decide I can no longer live with the vibration at these certain RPM range, right now we just stay out of these ranges and deal with it. Either way, dealing with it will be the cure for the next ??? years until my boat load of money lands.
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This is simple, so pay attention!
Your problem is that the shaft strut and engine mounts were NOT BUILT IN ALIGNMENT. This was common on these boats. No, more than common, it was the norm. To get the concept take a paper towel roller and shove a broom stick through it. See how little change it takes to make the broom stick come too close to the tube? Now think of one end supported by your shaft strut and the other by your engine. Adjust the engine AND the strut till the shaft passes cleanly through the tube with equal clearance on all sides and you'll have enough clearance. I had to do just this on my 1983 Hunter 33. The engine was too low and the strut was too high. I remounted the strut with 1/2" bolts in place of the 5/16", and used thickened epoxy as filler between the strut and mount pad on the hull. 3/4" plywood was added to the engine mount bed to bring the Yanmar engine mounts up to a point where the engine sat properly on them. End result? The shaft goes through the tube with equal clearance all around, both at the entry and the exit. The shaft does not bang on the stern tube except if I chop the fuel abruptly, which causes engine movement in excess of the clearance between the shaft and tube. Or just go out and buy a 1 1/2" twist drill bit at a cost of about $150.00 and whack open that hole. Then you won't have to adjust anything. Except while you're at it remount the bronze log that supports the stuffing box because that was most likely installed badly and misaligned just like mine. You can also decrease this annoyance by replacing your 2 cylinder with a smoother running 3 cylinder as I did.
Your problem is that the shaft strut and engine mounts were NOT BUILT IN ALIGNMENT. This was common on these boats. No, more than common, it was the norm. To get the concept take a paper towel roller and shove a broom stick through it. See how little change it takes to make the broom stick come too close to the tube? Now think of one end supported by your shaft strut and the other by your engine. Adjust the engine AND the strut till the shaft passes cleanly through the tube with equal clearance on all sides and you'll have enough clearance. I had to do just this on my 1983 Hunter 33. The engine was too low and the strut was too high. I remounted the strut with 1/2" bolts in place of the 5/16", and used thickened epoxy as filler between the strut and mount pad on the hull. 3/4" plywood was added to the engine mount bed to bring the Yanmar engine mounts up to a point where the engine sat properly on them. End result? The shaft goes through the tube with equal clearance all around, both at the entry and the exit. The shaft does not bang on the stern tube except if I chop the fuel abruptly, which causes engine movement in excess of the clearance between the shaft and tube. Or just go out and buy a 1 1/2" twist drill bit at a cost of about $150.00 and whack open that hole. Then you won't have to adjust anything. Except while you're at it remount the bronze log that supports the stuffing box because that was most likely installed badly and misaligned just like mine. You can also decrease this annoyance by replacing your 2 cylinder with a smoother running 3 cylinder as I did.
You know, I'm sorry, but I have owned my boat...
since she was new. When she was new, everything was aligned and she ran smooth in all rpms. So, don't assume Hunter did not do it right, maybe, there are other issues at hand. 1. Upon inspection, my shaft is bent. 2. Upon inspection, my prop is bent and prob. out of balance. 3. No matter how well the set up, if things are bent or out of balance, it's going to vibrate at certain rpms. So, even though yours might have been out, does not mean this is the normal situation, I remember when mine ran smooth and hopefully, it will again soon.
since she was new. When she was new, everything was aligned and she ran smooth in all rpms. So, don't assume Hunter did not do it right, maybe, there are other issues at hand. 1. Upon inspection, my shaft is bent. 2. Upon inspection, my prop is bent and prob. out of balance. 3. No matter how well the set up, if things are bent or out of balance, it's going to vibrate at certain rpms. So, even though yours might have been out, does not mean this is the normal situation, I remember when mine ran smooth and hopefully, it will again soon.
Got your attention, didn't I ??
Well, sometimes ruffling a few feathers is not a bad thing. The intention was to stimulate the thinking process, and it appears that happened. It appears we have two different people discussing the problem, Steven F. of Pt. Charoltte, Fl, and Arthur of Lake Lanier, Georgia. Steven and his two mechanics have given up after going to a certain point with no resolution. Arthur, on the other hand has found a bent shaft, bent prop and an out of balance condition. These are distinct, identified problems and not in the context being discussed here. Steven however still has his problem even after his mechanics supposedly ruled out those problems from the beginning as any competent mechanic would have. I certainly did not just assume Hunter did it wrong. I have done a good amount of discussion about this sort of thing with people who the boats and work on them, them and have no vested interests. Plain and simple: these boats were early PRODUCTION boats. There is very little on them that is even and symetric side to side or front to back. I've probably done more work on my boat than any three other Hunter 33 owners and I KNOW my hull, and I can tell you there is NO symetry. Chain plate mount points differ port and starboard, Backstay "U" bolt mounting points vary by about 6 inches. Hull thickness at the sharp "V" of the hull half way between the keel and the knuckle varies 3/8" port vs. starboard in a 2" hole. The deck thickness differs 1/2" port to starboard at the same relative point. Ever pull out the opening ports? Nicely cut holes, eh? (Mine must have been cut by a rabid butcher) So, you believe that every engine bed pan was glued in place perfectly and every strut was bolted in in perfect alignment to it. Well, I can tell you they it aint so. My 2GM banged the shaft against the shaft tube mercilessly. Alignment helped minimaly. Swapping the two cyl for a 3 cyl helpd. But I knew something just wasnt't right. After intense inspection and measurement with the boat out of the water I could see that the shaft did not pass through the hole concentricly over it's length. This necessitated the strut relocation. Now. Are there other factors? I think so. Arthur of Lake Lanier Georgia implies that the problem crept up on him. Ageing of the engine would explain this. As any engine accumulates hours it runs less smoothly and develops rough spots. The mounts also wear, allowing the engine to dance around. These factors undoubtedly account for a good bit of shaft banging. I Steven S.'s case I had to assume these factors had been looked at. The bottom line here? once you have exhausted the logical avenues, the obscure and seemingly unlikely has to be explored. And the way these boats were slapped together leads to the obscure and unlikely. Did I look at opening up the shaft tube to eliminate the problem? Of course I did, but I determined that on the 33 hull it would create more problems than it cured and more work than it was worth.
Well, sometimes ruffling a few feathers is not a bad thing. The intention was to stimulate the thinking process, and it appears that happened. It appears we have two different people discussing the problem, Steven F. of Pt. Charoltte, Fl, and Arthur of Lake Lanier, Georgia. Steven and his two mechanics have given up after going to a certain point with no resolution. Arthur, on the other hand has found a bent shaft, bent prop and an out of balance condition. These are distinct, identified problems and not in the context being discussed here. Steven however still has his problem even after his mechanics supposedly ruled out those problems from the beginning as any competent mechanic would have. I certainly did not just assume Hunter did it wrong. I have done a good amount of discussion about this sort of thing with people who the boats and work on them, them and have no vested interests. Plain and simple: these boats were early PRODUCTION boats. There is very little on them that is even and symetric side to side or front to back. I've probably done more work on my boat than any three other Hunter 33 owners and I KNOW my hull, and I can tell you there is NO symetry. Chain plate mount points differ port and starboard, Backstay "U" bolt mounting points vary by about 6 inches. Hull thickness at the sharp "V" of the hull half way between the keel and the knuckle varies 3/8" port vs. starboard in a 2" hole. The deck thickness differs 1/2" port to starboard at the same relative point. Ever pull out the opening ports? Nicely cut holes, eh? (Mine must have been cut by a rabid butcher) So, you believe that every engine bed pan was glued in place perfectly and every strut was bolted in in perfect alignment to it. Well, I can tell you they it aint so. My 2GM banged the shaft against the shaft tube mercilessly. Alignment helped minimaly. Swapping the two cyl for a 3 cyl helpd. But I knew something just wasnt't right. After intense inspection and measurement with the boat out of the water I could see that the shaft did not pass through the hole concentricly over it's length. This necessitated the strut relocation. Now. Are there other factors? I think so. Arthur of Lake Lanier Georgia implies that the problem crept up on him. Ageing of the engine would explain this. As any engine accumulates hours it runs less smoothly and develops rough spots. The mounts also wear, allowing the engine to dance around. These factors undoubtedly account for a good bit of shaft banging. I Steven S.'s case I had to assume these factors had been looked at. The bottom line here? once you have exhausted the logical avenues, the obscure and seemingly unlikely has to be explored. And the way these boats were slapped together leads to the obscure and unlikely. Did I look at opening up the shaft tube to eliminate the problem? Of course I did, but I determined that on the 33 hull it would create more problems than it cured and more work than it was worth.
thanks Sam
Thanks for everyone's response, all have valid points. When she is hauled next time I will have a bunch of stuff examined to hopefully fix this nagging problem once and for all. I doubt that a tube replacement is in our future, I'm confident that the solution lies elsewhere... One last question, does the rudder need to be removed to remove the drive shaft on the 33's?
Thanks for everyone's response, all have valid points. When she is hauled next time I will have a bunch of stuff examined to hopefully fix this nagging problem once and for all. I doubt that a tube replacement is in our future, I'm confident that the solution lies elsewhere... One last question, does the rudder need to be removed to remove the drive shaft on the 33's?
Similar problem
It had a similar experience. Two years ago I had my motor mounts changed. The mechanic could not get the shaft to align. Then followed a new shaft, new cutlass bearings, and new dripless shaft seal. The result was a shaft that was tight and binding between the cutlass bearing and the stern tube. The prop strut had to be rebedded and realigned to free up the shaft in the stern tube. Then the engine could finally be aligned to the shaft. Don't assume that any one component in a system can be changed without an impact on the entire system.
It had a similar experience. Two years ago I had my motor mounts changed. The mechanic could not get the shaft to align. Then followed a new shaft, new cutlass bearings, and new dripless shaft seal. The result was a shaft that was tight and binding between the cutlass bearing and the stern tube. The prop strut had to be rebedded and realigned to free up the shaft in the stern tube. Then the engine could finally be aligned to the shaft. Don't assume that any one component in a system can be changed without an impact on the entire system.
Yes, either you have to.....
drop the rudder or you have to remove the strut so that you have the clearance to pass the shaft by the rudder. I dropped my rudder since I did not want to have to rebed the strut. Dropping the rudder is not a bad thing, it gives you access to areas of of the hull otherwise not accessible. I will be putting things back together next week, we are now finished with blister repairs, barrier coat, bottom paint and will be reinstalling the shaft, prop then the rudder. While the rudder has been off, I've been able to really fair and barrier coat it in all areas making sure of a good epoxy seal between the rudder shaft and fiberglass rudder body.
drop the rudder or you have to remove the strut so that you have the clearance to pass the shaft by the rudder. I dropped my rudder since I did not want to have to rebed the strut. Dropping the rudder is not a bad thing, it gives you access to areas of of the hull otherwise not accessible. I will be putting things back together next week, we are now finished with blister repairs, barrier coat, bottom paint and will be reinstalling the shaft, prop then the rudder. While the rudder has been off, I've been able to really fair and barrier coat it in all areas making sure of a good epoxy seal between the rudder shaft and fiberglass rudder body.
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