Hi all,
My sailing partner and I (both quite experienced sailors, he owned a new Hunter 34 the first year they came out and i sailed my Sabre 28 for ten years) just purchased a beautiful, well maintained, 1984 Hunter 34. Yanmar diesel runs like a top in neutral and under power. On our first 4 sails using the engine to both motor and motor sail things went peachy. Boat has a Yanmar 3GMF with a fixed 15 x 15 prop.
Then on about our fifth sail as we prepared to drop the main, we rather suddenly noticed a severe vibration at about 1500 rpm as we powered up to get to the dock. Didn't sound like either a loose zinc which in my Sabre 28 experience is a more hammer like bang bang bang until it threw itself off, but rather more like the hard thump thump of picking up a lobster buoy, along with the motor really almost bouncing in it's bed at that rpm, only to go immediately away as we throttled down..
Thing is we don't believe we hit a buoy, except that the tide was flowing out very had and they were in some cases pushed slightly below the surface by the tide so it might be possible we clipped a submerged one (but we both doubt it). Neither of us heard any thump (one of us happened to be at the helm and one lying on the bow.
After docking (we still had power and had vibrationless motoring under 1500) I dove on the prop, and to my dismay did not find the hoped for loose zinc, lobster buoy, or visibly bent shaft or prop that was expected.
After tying up, we powered up again to 1500 and again the vibration and sound came back, but only in forward, not in neutral (we took the engine to almost 2800 rpm in neutral) or reverse (didn't rev reverse quite that high).
Fortunately we are having the boat hauled on Thursday as it is the end of the season. so we can get a good look while it's on the "hard" for the winter. Idea? Yanmar engine trouble shooting guide talks about engine misfires, motor mount looseness (not checked yet), prop imbalance and shaft alignment in that order. (it does have an apparently plastic shaft saver in the drive chain and I observed both it and the stuffing box and coupling at 1500 during the vibration and couldn't see anything obviously wrong) and I also held on to the two bolts ends which protrude into the hull which mount the prop shaft and they didn't seem to be vibrating, but the vibration did seem to originate just below that area).
Seems the vibration shouldn't shouldn't be engine misfires as it is still smooth as silk to 2800 rpm in neutral (we didn't try to push it beyond the vibration at 1500 to see if it would settle down above 1500). The cutlass bearing seemed to be good with no play two weeks ago when we had it hauled to do the marine survey (it has been replaced at least twice (maybe more) by its two previous owners in its 20 something years), there is one old removed shaft saver some where on the boat I saw during the survey, so it has been replaced at least once in it's life)....so ideas?
Can cutlass bearings fail so suddenly, can lobster pots be hit without one knowing hard enough to bend a shaft or prop, or can motor mounts fail suddenly? ideas!! please Help!!! Chuck
My sailing partner and I (both quite experienced sailors, he owned a new Hunter 34 the first year they came out and i sailed my Sabre 28 for ten years) just purchased a beautiful, well maintained, 1984 Hunter 34. Yanmar diesel runs like a top in neutral and under power. On our first 4 sails using the engine to both motor and motor sail things went peachy. Boat has a Yanmar 3GMF with a fixed 15 x 15 prop.
Then on about our fifth sail as we prepared to drop the main, we rather suddenly noticed a severe vibration at about 1500 rpm as we powered up to get to the dock. Didn't sound like either a loose zinc which in my Sabre 28 experience is a more hammer like bang bang bang until it threw itself off, but rather more like the hard thump thump of picking up a lobster buoy, along with the motor really almost bouncing in it's bed at that rpm, only to go immediately away as we throttled down..
Thing is we don't believe we hit a buoy, except that the tide was flowing out very had and they were in some cases pushed slightly below the surface by the tide so it might be possible we clipped a submerged one (but we both doubt it). Neither of us heard any thump (one of us happened to be at the helm and one lying on the bow.
After docking (we still had power and had vibrationless motoring under 1500) I dove on the prop, and to my dismay did not find the hoped for loose zinc, lobster buoy, or visibly bent shaft or prop that was expected.
After tying up, we powered up again to 1500 and again the vibration and sound came back, but only in forward, not in neutral (we took the engine to almost 2800 rpm in neutral) or reverse (didn't rev reverse quite that high).
Fortunately we are having the boat hauled on Thursday as it is the end of the season. so we can get a good look while it's on the "hard" for the winter. Idea? Yanmar engine trouble shooting guide talks about engine misfires, motor mount looseness (not checked yet), prop imbalance and shaft alignment in that order. (it does have an apparently plastic shaft saver in the drive chain and I observed both it and the stuffing box and coupling at 1500 during the vibration and couldn't see anything obviously wrong) and I also held on to the two bolts ends which protrude into the hull which mount the prop shaft and they didn't seem to be vibrating, but the vibration did seem to originate just below that area).
Seems the vibration shouldn't shouldn't be engine misfires as it is still smooth as silk to 2800 rpm in neutral (we didn't try to push it beyond the vibration at 1500 to see if it would settle down above 1500). The cutlass bearing seemed to be good with no play two weeks ago when we had it hauled to do the marine survey (it has been replaced at least twice (maybe more) by its two previous owners in its 20 something years), there is one old removed shaft saver some where on the boat I saw during the survey, so it has been replaced at least once in it's life)....so ideas?
Can cutlass bearings fail so suddenly, can lobster pots be hit without one knowing hard enough to bend a shaft or prop, or can motor mounts fail suddenly? ideas!! please Help!!! Chuck