vibration/alignment

Have you had a diver check your prop or cutlass bearing, you could have a damaged prop(bent or even missing a blade or part of one) which could vibrate to the point your cutlass gets worn badly, then everything could be flopping around and the main receiver of all this would be that coupler. Have you hauled your boat and checked the shaft, it could be slightly bent? A diver can grab the prop blade and shake it and check for worn out cutlass bearing, it should be snug and have no play. Also, your prop may have struck something, and perhaps your strut is bent(if you have one). Just some things I've observed at boatyards, and even after you haul a boat and do shaft work you put the boat in the water and do an alignment 24 hours later after the hull has resumed its waterborn shape. There should be no vibrations after that, or you do the alignment until you get it right. The coupling between the engine and the dampener should be within .002 when you disconnect them. (the shaft has to be checked to be sure it is not moving) Then you adjust your engine to correct the alignment. It would be good to check this before you harm your engine or yourself..... Helen (p.s. one time a commercial salmon boat I half-owned had wrapped a piece (long piece) of polypro line from some lost crabpot around the shaft between the prop and the bearing and it melted on hard and luckily got diagnosed before it pulled that prop shaft right out of the boat.)