Prop Question

Discussion in 'Bubba's Outboards' started by Foxhound, Aug 9, 2006.

  1. Foxhound

    Foxhound New Member

    Messages:
    403
    State:
    Georgia
    Recently replaced the aluminum prop on my 2005 60 hp Mercury big foot four stroke engine with the same size stainless steel prop. The problem is when I shift it into gear (fwd. or rev.) I feel a slight vibration that I didnt have with the aluminum prop. It goes away as soon as the motor starts to spool up and is fine at any other speed.......its just the inital putting it in gear that I dont like. The stainless prop I bought is made by Power Tech. Any ideas ???
     
  2. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Ken, be sure your stainless prop is not making contact with any part of your lower unit housing at idle. Pull the prop and look for rub marks on the inner portion of the lower unit.

    Grab ahold of your prop shaft and try to wiggle it, checking for any play.

    Was your aluminum prop damaged?
     

  3. trnsmsn

    trnsmsn New Member

    Messages:
    1,214
    State:
    Missouri Originally Now I
    Good Morning Bob, JAT....... Could The Additional Weight Of The Stainless VS The Aluminum, Have Enough Load Effect For Something Such As Dirty Injectors(Tip-In) Problems To Surface ?:roll_eyes:
     
  4. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Anything's possible. Injector? I think it would show up with the aluminum also.

    There's balance issues to consider, added weight, possible prop shaft damage. Just waiting to hear back on why the prop change.

    Also, would like to know about tach readings with the stainless vs the aluminum.
     
  5. Foxhound

    Foxhound New Member

    Messages:
    403
    State:
    Georgia
    Bob
    I pulled the stainless prop back off and everything looks fine as far as rubbing. The aluminum prop was not damaged.....just thought Id take the opportunity to upgrade to stainless. The prop shaft has no axial play at all. The vibration comes at the very instant you shift into gear but goes completely away as soon as the throttle is advanced. Could this be a manufacturing harmonic defect with the prop ??? I was skeptical about purchasing this prop due to the price versus the original Mercury replacement prop.....about half the price. Thanks for all the input.
     
  6. Ryan

    Ryan New Member

    Messages:
    65
    State:
    Crystal, Minnesota
    I've heard about this happening to people before, especially with lower hp motors. I've been told it's due to the extra weight of the SS prop. I'm sure that you're SS weighs 4 times as much as the aluminum one. I think it's pretty normal and wouldn't worry about it if it's just when you shift and it goes away once you get on the throttle.
     
  7. blackwaterkatz

    blackwaterkatz Active Member

    Messages:
    3,659
    State:
    Andrews, SC
    Probably nothing to be concerned about, Ken. How much time do you spend in gear, idling, anyway? Do you notice any difference in the idle rpm's with the new prop vs the old one? The heavier prop may add a little something that wasn't there, and affect the idle. If it was a serious balance problem, it would get worse as speed increased, wouldn't it?
    Mine does similarly, always has, but I think it is just moving from no-load idle to the prop-load????
    Hey, if I see you Friday, we'll check it out. :big_smile:
     
  8. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Sure there's harmonics that play a roll in prop rpm, some engines more than others and it can get extreme.

    A worked on 2 200 hp merc engines a few yrs ago that came in on different days, different boats.

    Both had the same problem, all the machine bolts that hold the stator in place were sheared off, 5 I think there was in each stator.

    Two things similar in both those engines was that they both had 5 blade exactly the same SS props. Harmonics, maybe?
     
  9. savage308

    savage308 New Member

    Messages:
    399
    State:
    Victoria, Texas
    Put a table, bricks, etc under your prop, measure the distance from the bottom of the blade to the table or whatever you used under the prop. (make sure your blade will not touch whatever you put under them but you want it as close as you can get it) turn the prop and check each blade.... The distance should be the same so you will be able to tell if your prop shaft is bent, or if your prop has been damaged....
     
  10. Dragger

    Dragger New Member

    Messages:
    538
    State:
    North Carolina
    Ryan is rite on this one, It happens in lower HP motors,due to weight of the prop. You lose app. 1 1/2 to 2% HP when going to stainless. ( at low speed) It takes HP to pull weight, Run the crapp out of it and don't worry about it............