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  1. #1

    Outboard vibration through boat??

    Hi all.

    Chasing some wisdom if possible - yesterday was the maiden voyage of my 4.8 ally CC after strapping on a new DF70 Suzuki. Motor was a gem, however it quickly became apparent that there was a resonance/vibration running through the entire boat once the revs got into the thousands. Not an engine problem, just a vibration through the boat.

    Not only did I eventually realise that much of the noise whilst underway was actually the 'humming' but a good example was that whilst we were cruising along at say 3800, I could go and put my hand anywhere up the bow and feel the vibes well and truly. Can't really think of anything else IN the boat that would be vibing enough to transfer through the boat other than the engine itself.

    Now, I am hazarding a guess that this isn't good for an ally boat in the long term, but the question is this - what are the likely culprits and is it possible that the shiny new Suzi prop (I am guessing it is??) has a balance issue which is causing this?? I'll be delighted if it's something that simple...

    Any thoughts would be appreciated. First service coming up soon, so will be talking to the dealer obviously, but would love to know some scenarios.

    Regards,
    Seb

  2. #2

    Re: Outboard vibration through boat??

    The prop would be the first thing i'd look at. I've had props that look perfect, but shook the boat to bits!

  3. #3

    Re: Outboard vibration through boat??

    Thanks mate - certainly hoping it might be as simple as that!!

  4. #4

    Re: Outboard vibration through boat??

    Put the leg into a tank and when you put the motor into gear if you have any prop slap it will be quite audible, but in saying that once underway that can disappear. I would also go back to the dealer now and see if he would allow you to try a different prop as there could be other issues down the track that won't occur until after warranty has expired.

  5. #5

    Re: Outboard vibration through boat??

    I am interested to check if there's any vibes out of gear at a couple of thou RPM too, but yep, definitely interested to hear their views!

  6. #6

    Re: Outboard vibration through boat??

    There's an app for that if you've got a smart phone & a window sucker.
    Given that you know your rpm, gearbox ratio, # of prop blades & any drive reduction on the Zuke then the app may help you pin point the type of vibration by the frequency.
    In addition to vibrations it also does sound via the smart phone mic.
    My practice screenshots & vibration recordings loaded into excel to get a readable graph from all the numbers.
    Attached Images Attached Images

  7. #7
    Ausfish Bronze Member 552Evo's Avatar
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    Jul 2016
    Location
    Melbourne

    Re: Outboard vibration through boat??

    Thatís pretty cool Fed. I use a similar method at work sometimes using accelerometers to monitor bearing and gear wear/damage.


    Saltwater fishing, boat mad but has a job that gets in the way.

  8. #8

    Re: Outboard vibration through boat??

    Yeah Evo, pretty cool for a $3 app.
    I'm chasing an 80-100 KMH vibration in my car & have already eliminated the tailshaft while simply playing with the app to figure out how it all worked.
    The $3 app https://play.google.com/store/apps/d...pps.Vibrations
    or the $550 app https://play.google.com/store/apps/d...jacobkelly.nvh
    My Missus thinks I'm a nut putting my phone on the washing machine & fridge etc.

  9. #9

    Re: Outboard vibration through boat??

    Are the engine mount bolts tight as in torqued evenly? Is there major transom flex which can be easily checked by lifting the leg from the bottom when it is fully up? If the transom moves when you lift the leg that may be an issue. Have you upgraded from a lighter engine?
    ROLL TIDE, ROLL.................

    Regards,
    Peter


    http://www.superiorterminals.com.au

  10. #10

    Re: Outboard vibration through boat??

    Quote Originally Posted by Fed View Post
    Yeah Evo, pretty cool for a $3 app.
    I'm chasing an 80-100 KMH vibration in my car & have already eliminated the tailshaft while simply playing with the app to figure out how it all worked.
    The $3 app https://play.google.com/store/apps/d...pps.Vibrations
    or the $550 app https://play.google.com/store/apps/d...jacobkelly.nvh
    My Missus thinks I'm a nut putting my phone on the washing machine & fridge etc.
    What type of car Fed?
    "I soak the worms in rum. The fish love em and the worms die happy"
    "Alcohol is not the solution to your problems...................but then again, neither is milk"

  11. #11

    Re: Outboard vibration through boat??

    That's a pretty nifty app alright!!! Peter, will have a look but was interested as to what the torque was like on the bolts as they are the main connection to the boat. Yep, upgraded from a Merc 60, but transom should be fine given it's an alloy boat. Will be ringing dealer tomorrow so curious as to their first thoughts, but all to be looked at during first service. Thinking I might grab a SS Solas prop in the mean time. Can't hurt right?

  12. #12

    Re: Outboard vibration through boat??

    I think my new ss Solas prop is out of balance as made the engine and boat vibrate, yet to take it back but put the old prop back on and no problem with vibrations

  13. #13

    Re: Outboard vibration through boat??

    Hmm...bugger. Anyone able to suggest a similarly priced alternative when it comes to props?

  14. #14

    Re: Outboard vibration through boat??

    Quote Originally Posted by seb7701 View Post
    Hmm...bugger. Anyone able to suggest a similarly priced alternative when it comes to props?
    I'm sure they are not all unbalanced but just saying even the "best" brands can be!

  15. #15

    Re: Outboard vibration through boat??

    What type of car Fed?
    Sent you a PM scottar, don't want to pollute Seb's thread.

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