I had been feeling this intermittent vibration coming throught the floor of my Cobia 184 CC lately. Took it to a pro and he said it was the prop bushing. Okay , so I take the prop off and the guy at the shop says the spline inside the hub is worn and my shaft could be hosed as well. Any way of knowing if the shaft is ok or not ? I have vernier, I could measure the OD but to me it looks fine.