Strange Noise??? – Dry Cutlass Bearings!!!

2010 January 22
by Chris Brown
Running with cool bearings
Running with cool bearings

A week ago I got a call from a Captain on a 120′ Sovereign that was experiencing a very troubling vibration problem.  He had already had a vibration analysis company survey the boat and had another yard pull the shafts and replace all cutlass bearings.   The sound was coming from the port side shaft and was described as an audible “zupe….zupe….zupe”.

Since he was in Fort Lauderdale I agreed to go for a short sea trial to listen and feel.  The sound was very apparent during the initial idle down the intercoastal waterway, however, it was intermittent.   After a few minutes of crawling with ears to the floor and bulkheads the location of the sound was narrowed to the cutlass bearing located in the aft end of the stern tube.  The sound and vibration was consistent with the shaft frequency.  It occurred at all different RPM ranges (we went offshore for more speed) but continued to be intermittent.  The sound was not a common prop or bearing sing – nor was it a hopping vibration consistent with a bent shaft.  It was a rubbing sound.
After a careful inspection of the engine room and a run-down on the history of the recent engine work we diagnosed the problem as dry stern tube cutlass bearings.  The cooling line that runs from the engine to the Tides shaft seal also serves to deliver water to the cutlass bearing in the stern tube.  It sounded like it was not delivering enough water to keep the bearing lubricated at all times.  The “zupe” sound was the SS shaft dragging on the dry rubber of the cutlass bearing.
The ships engineer replaced the cooling hose to the Tides seal system.  The old hose and fittings showed signs of blockage.  A total investment of  $20 for new hose and an hour of time in the engine room was all it took to resolve the problem.  Consistent water going to the bearings kept it cool and lubricated at all RPMs.
It is personally gratifying to help a customer fix a problem and enjoy their boat regardless of the size of the job.  The captain and owner were very happy to get the problem fixed and dodge another big yard bill while High Seas adds another customer to our growing reference list – oddly, we have this reference for the work that we did not do (haul-out, remove shafts…..)   Since the sound was intermittent and bearings were just replaced a few engine hour ago we assume, at this time, that the bearing was not wiped out and the customer avoided the problem experienced in this blog on dry Thordon Bearings on the 135′ Intermarine or in this blog on dry Cutlass Bearings on the 123′ Feadship.
Happy Sailing
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