Tiara Vibration Problems – Cutlass Bearing Spacing

2009 November 1
by Chris Brown

We just finished an interesting project on a 52′ Tiara Express Cruiser.  This boat came to High Seas after other mechanics failed to fix a major vibration problem.  During sea-trial and subsequent dial indicating measurements it was obvious that there was an engine alignment problem.   This is a v-drive engine which makes engine alignments very difficult – you must make engine mount adjustments that are opposite of the common approach which can confuse even the most experienced mechanic.   Engine alignments by prior mechanics were probably done in the water which will not help if the transmission flange is not aligned with the shaft tube.   Go here for more info on alignments….

During our disassembly we measured the distance from the single cutlass bearing in the strut to the coupler on the transmission.  We found the distance far exceeded the recommended distance between bearings as calculated in the Aquamet Crucible guide.  Any vibration from a misalignment or bent shaft would be exaggerated by a shaft whip condition.  Our solution – straighten the shafts, align the motors and add a half cutlass bearing in the stern tube.  Not a complicated or expensive solution.

The results speak for themselves.  It only took a few minutes of sea-trial running the boat at cruise and WOT to feel a big difference in the smoothness of the ride.

Another happy customer and problem solved.

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