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Navigator Vibrations

Discussion in 'Technical Discussion' started by billybobs, Aug 18, 2006.

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  1. billybobs

    billybobs New Member

    Joined:
    Aug 18, 2006
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    Location:
    New Castle, NH
    I have been trying for four years to stop the engine/shaft/propeller vibrations on a 48 navigator Classic motoryacht. Has anyone out there had a problem like this with these boats and have you found a solution?

    Obviously, alignment has been done many times. Shaft log/strut alignment has been laser checked.

    Possible considerations: wheels too big; soft engine mounts not designed for the load.

    Any help greatly appreciated.
  2. CaptTom

    CaptTom Senior Member

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    Palm Beach to Ft Lauderdale
    Have you tried an isolation dampner betweenthe tranny and shaft? Seen them advertised, it's a rubber mount that bolts betweenthe two. Never used one but worth considering. Also make sure the coupler on the tranny is not warped or bent.
    Good luck.
    Capt Tom
  3. ychtcptn

    ychtcptn Senior Member

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    Location:
    Lighthouse Point, FL
    It could be as simple as your props not being balanced. Have them Dynamically balanced and prop scanned to make sure they are the right shape.

    While you have the props off, run the engine in gear up to speed and see if the engine is shaking (do you notice and shaking/vibration while you are running?)

    I have just spent the last month correcting this problem on yacht that was run aground hard previous to my command.
  4. Aquaventures

    Aquaventures New Member

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    Ft. Lauderdale, FL
    I am a broker in Ft. Lauderdale that took a 2000 Navigator 53 in trade on a larger boat. The Navigator had some vibration issues and here is what we did to correct them: Sent the props out and had them balanced. Checked and adjusted motor alignment. Removed the shafts and had them trued. Truing the shafts had the biggest impact. When we put everything back the vibration was gone and the boat ran very smooth. S&S Diesel in Ft. Lauderdale did the work.
  5. billybobs

    billybobs New Member

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    Thank you aquaventures.
  6. billybobs

    billybobs New Member

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    Location:
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    Interesting thought. We've run the engines up in neutral which of course tells you nothing about the driveline. Unfortunately my boat yard has an antiquated way of hauling and resplashing the boat with the props off just to run it up in gear would probably take about half a day. Maybe we can think of another way.

  7. Jamie Agnes

    Jamie Agnes New Member

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    Apr 16, 2007
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    Location:
    Northpoint Marina
    Navigator

    I have a Navigator 48 Classic and was wondering if you
    have any exhaust problems with your boat.:
  8. billybobs

    billybobs New Member

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    If, by exhaust problems, you mean sooting, the answer is yes. As I loaded the boat for cruising the original props would no longer let the engines get close to rated rpm and they were overfueling and sooting. Took two inches of pitch out of the props and that helped but not enough. Now have smaller diameter props on order and hope that cures the problem. At any rate, that will get the prop diameter correlated with the shaft diameter in accordance with ABYC specs. Factory props were too big for the shaft.
  9. James H

    James H New Member

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    San Francisco bay area
    I am a surveyor in the SF Bay area. I just went on a seatrail today and found the top exhaust on the port side was running much warmer then the starboard side. but only after the Y. And only below 1500 RPM's, engine speeds higher then that the fiberglass exhaust Y and hose would cool down to equalize with the lower. Other then that the engine ran Volvo ran flawless and all other temps and pressures were normal.Has anybody come across this or had issues with this?
  10. Capt J

    Capt J Senior Member

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    You really don't want to reduce prop diameter. Who took 2 inches of pitch out of the props, were they dynamically balanced? I'd take the boat out and leave 1 engine in neutral, put the other up to 1000 rpms, then say 1800 rpms or near cruise and see if there's a vibration, also note how many rpms each one turns (only for a minute) see if one side has vibration and not the other or one engine is not making rpms
  11. Pascal

    Pascal Senior Member

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    I d start looking at a lack of water flow either impeller or restriction along the way. Every time I've had an impeller getting weak, the first sign was always high gear temperature at low rpm. Increase speed and gear temp woudl come down. Never measured te exhaust temp but woudlnt be surprised if it was higher too
  12. 30West

    30West Member

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    Agree. At higher hull speed your scoop strainers are pushing water through the raw water system regardless of condition of your impellers. This could just be a warning sign.
  13. PacBlue

    PacBlue Senior Member

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    What is your issue other than a difference in exhaust temps in your data?
    Does the exhaust system show any abnormal wear and how many hours on each engine?
    One engine is a direct dump to the outboard exhaust tubes and the other is routed from centerline to outboard, which one has the higher temp?
  14. FIQ

    FIQ Member

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    Location:
    Olympia, Wa
    What year is your Gator?
    Some of the 2005-2009 boats had undersized engine mount bolts.
    A friend of mine had a couple break! Bit of a vibration there!
    If your mount bolts are defective (stretched?), maybe the engine is doing some vibration at higher rpms.
    I'm sure that you looked at them at speed with ear muffs, eh?

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