jcpa
Well-Known Member
With the boat on the drying grid, I found the noise and much of my vibration probably was indeed caused by the shaft anode. One bolt had totally vanished, and the anode was rattling away against the P-bracket. I couldn’t see any obvious damage, so I simply found a new bolt and tightened it up properly. Motoring back to my mooring the bulk of my problem seemed to have gone away.
But then I went back to that flexible coupling. Norris had said that with the coupling removed, I should be able to slide the propshaft forward until the flange engaged with and touched faces with the gearbox flange; maybe one of my flanges had been changed by whoever inserted the flexible coupling. In my setup, the shaft nut fixing the gearbox flange extends about 5mm proud of the flange face, and the propshaft sticks out about 5mm proud of the other flange. I decided to close much of the resulting 10mm gap using four nuts as spacers between the two flanges, meaning I could then use a feeler gauge to measure the misalignment. Remembering that I had previously made a considerable eyeball tilt of the engine, the misalignment was still around 140 thou over the 3” distance between flange bolts! By my calculations, I’d need to move the front engine mounts to the very top of their threads to get near the adjustment needed.
A quick call to the Yanmar engineers, and they said that would be OK - I could then install the R&D coupling to take up any remaining misalignment (and they agreed the mounts had probably vibrated themselves down – remember they were originally at the bottom of their threads). They also said that the flanges sounded like the originals, but I should ideally try to pull the propshaft flange back up the shaft a bit so that the end of the shaft was well inside the flange face, and I could then bring the two flanges together properly to check the basic alignment.
That sounds like a job for winter; for now I’ve just adjusted the alignment down to somewhere near 10 thou vertically and horizontally (within the limits of my nut-spacer technique!), and reinstalled the original flexible coupling (until I can get to the Yanmar shop for the R&D one). I’ve only tested the engine/shaft assembly at low power (while moored to pontoon), but it seems to me to sound sweeter – and there’s no anode rattle!
Job NOT done, but I think I can use it carefully until lift-out in mid October.
Thanks all for your helpful advice and comments.
But then I went back to that flexible coupling. Norris had said that with the coupling removed, I should be able to slide the propshaft forward until the flange engaged with and touched faces with the gearbox flange; maybe one of my flanges had been changed by whoever inserted the flexible coupling. In my setup, the shaft nut fixing the gearbox flange extends about 5mm proud of the flange face, and the propshaft sticks out about 5mm proud of the other flange. I decided to close much of the resulting 10mm gap using four nuts as spacers between the two flanges, meaning I could then use a feeler gauge to measure the misalignment. Remembering that I had previously made a considerable eyeball tilt of the engine, the misalignment was still around 140 thou over the 3” distance between flange bolts! By my calculations, I’d need to move the front engine mounts to the very top of their threads to get near the adjustment needed.
A quick call to the Yanmar engineers, and they said that would be OK - I could then install the R&D coupling to take up any remaining misalignment (and they agreed the mounts had probably vibrated themselves down – remember they were originally at the bottom of their threads). They also said that the flanges sounded like the originals, but I should ideally try to pull the propshaft flange back up the shaft a bit so that the end of the shaft was well inside the flange face, and I could then bring the two flanges together properly to check the basic alignment.
That sounds like a job for winter; for now I’ve just adjusted the alignment down to somewhere near 10 thou vertically and horizontally (within the limits of my nut-spacer technique!), and reinstalled the original flexible coupling (until I can get to the Yanmar shop for the R&D one). I’ve only tested the engine/shaft assembly at low power (while moored to pontoon), but it seems to me to sound sweeter – and there’s no anode rattle!
Job NOT done, but I think I can use it carefully until lift-out in mid October.
Thanks all for your helpful advice and comments.
