Conference unifix::sailing

1814.0. "noise & vibration" by JUPITR::KTISTAKIS (Mike K.) Fri Nov 22 1991 11:10

    This note is for a fellow I came in contact with thru CW's second 
    opinion four years ago when I was buying my boat.(We both own 
    DownEasterns 32.Since then he has kept in touch.
    He called me at the beginning of last summer and told me of a grinding
    noise he had arount the propeller,cutlass bearing area when he was 
    reving around 1500 rpm's. Below 1500 rpm everything was normal,no noises.
    Above 1500 the grinding noise would increase and he also would
    experience a lot of vibration.At the time I told him to check the
    engine mounts for proper shaft allignment and to feel the shaft for
    any play for worn cutless bearing.
    He called me a couple days ago very puzzled.
    He has replaced the shaft, the cutlass bearing and has tried,at the 
    advice of some experts, three different propellers and the original
    problem still remains exactly the same.
    The engine is a Westerbake and he never had that problem before and
    he didn't change anything prior to the problem that would effect
    the engine,shaft or propeller.
    I told him that I place a note in this file and maybe we get some
    new leads.I also told him to check inside the ceramic..? tube the
    shaft goes thru before the cutless bearing ,I think that tube is
    called log, for any debris Any other suggestion would be appresiated.
    
    
    
    
    
     

How about a bad transmission bearing or damaged gear teeth? An input 
shaft bearing in my old truck's transmission once failed. At first, it 
only yowled at high speed under acceleration. As it got worse, it made 
noise all the time.

    I assume that there is no noise when the trasmission is in neutral so
    that eliminates any engine related problems.  I is not likely to be the
    propeller since that was not changed when the problem started, however
    it could be a bent blade if it struck something.  The cutlass bearing
    would seem most likely.  Is it loose in its mount? Is the shaft worn
    inside the bearing? 
    
    The stuffing box is a possibility.  
    The transmission bearing is also a possibility.  I
    would disconnect the prop shaft at the coupling just behind the
    transmission.  If the noise remains, then it is the transmission. If it's
    gone then the noise is the cutlass bearing, stuffing box or propeller. 
    Reving up the engine with the prop removed will eliminate that
    possibility.  Backing off the stuffing box nut will isolate that,
    leaving only the cutlass bearing.
    
    Good luck