Just got Golden Phoenix back from the boatyard. It was a Ya2K problem (Yet another $2K), and one that might interest CD powerboat owners.
I started taking the boat to a really good engine place. They found that the prop shafts were sticking a few thousandths of an inch out of the couplings, causing them to bump the transmission coupling. Also, the couplings themselves were not faced fairly. They were slightly cone shaped. In other words, the faces of the shaft couplings that mate with the transmission coupling were slightly closer to the transmission in the middle - about 8 thousandths - than on the edges.
Apparently they were this way since the boat was built - they couldn't find any sign that they had worn. Anyway, they refaced the couplings, which allowed them to do better engine alignment, and there has been a HUGE reduction in vibration - there's not much more now at WOT than at cruising speed, and there used to be plenty more. (Some of this might have been due to balancing the shafts as well, but that's been done before and it didn't have this effect.)
Has anyone else run into this one?
bilofsky@toolworks.com
CD 30 Power - Ya2K Problem: Shaft Coupling and Vibration
Moderator: Jim Walsh