Replacing Plastic Tensioner with Metal

picturethispicturethis Member Posts: 103 ✭✭
edited May 2014 in Engine Discussions
The bearing in the plastic tensioner pulley is going bad on my 2000 7.4 MPI . I was going to replace it with a metal pulley with a larger sized bearing (same size pulley) 

Is there any reason i shouldn't do this?
I am a new boater with my first boat,  thats why some of my questions seem dumb
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  • 212rowboat212rowboat Member Posts: 2,593 ✭✭✭✭✭
    What kind of metal? :-)
    click here for faults (BEEP) list
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  • picturethispicturethis Member Posts: 103 ✭✭
    guessing steel
    I am a new boater with my first boat,  thats why some of my questions seem dumb
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  • 212rowboat212rowboat Member Posts: 2,593 ✭✭✭✭✭
    I'd stick with plastic/nylon.. steel will corrode and/or rust at the first opportunity, and is destined to fly apart at high engine speed, making you some issues you'll not appreciate. A sealed bearing may be okay, though more expensive than nylon..
    click here for faults (BEEP) list
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  • picturethispicturethis Member Posts: 103 ✭✭
    edited May 2014
    Its strange that they use a plastic pulley on the tensioner but all the other pulleys are metal on the serp belt
    I am a new boater with my first boat,  thats why some of my questions seem dumb
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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    A bigger bearing is not always better, these are all sealed bearings for that application, but you have to mind bearing rpm limits under the load it carries and it will have more drag too. Unless the bearing is failing from loads / L-10 life issues, and very doubtful that is the case; these bearings have a life based on the grease used in them and they break down from that and/or seal failure (contamination). Bigger will not solve that problem.

    A metal pulley will rust and then you will get squeaks from the belt too. Eeek. Eeek. Eeek.

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • picturethispicturethis Member Posts: 103 ✭✭
    thats a good point about the bigger bearing and having the motor work harder.

      thanks for the info guys
    I am a new boater with my first boat,  thats why some of my questions seem dumb
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  • girls2watergirls2water Member Posts: 14 ✭✭

    I had this pulley break this weekend it broke in half and I am also trying to figure out what to replace it with and if I should replace the full pump.  I have learned that on the 5.7 merc bravo 3 that there is supposedly a kit with metal pulley and new belt.  Service rep says the old belt won't fit with new pulley.  The new full pump has a metal pulley however and no one has said a new belt will be needed.  I would like to see more discussion on why the plastic was used.  It seems like  you all are saying it is better for noise.  Thoughts around these issues?  Thanks guys


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  • Dream_InnDream_Inn Member, Moderator Posts: 7,663 mod
    I know several in my marina that replaced them with metal.  They all have been much happier.

    Dream 'Inn III -- 2008 400 Express

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  • georgec14georgec14 Member Posts: 16 ✭
    have had the plastic pulley since 2004 /been replaced once ,never had a problem.
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