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Merc Bravo 111 Issues

Discussion in 'Technical Discussion' started by Fishtigua, Mar 11, 2012.

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  1. Fishtigua, Mar 11, 2012
    #1
    Fishtigua

    Fishtigua Senior Member

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    I've got a Merc Bravo3 mated to a V8 supercharged GM diesel that keeps stripping it's gears.

    Any ideas as to what ratio and load rating I should looking at to improve it?
  2. AMG, Mar 11, 2012
    #2
    AMG

    AMG YF Moderator

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    Do you have the external water spray to cool the drive?
  3. Fishtigua, Mar 11, 2012
    #3
    Fishtigua

    Fishtigua Senior Member

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    Nope, just the normal pick-up. It's not a X-drive either.
  4. K1W1, Mar 11, 2012
    #4
    K1W1

    K1W1 Senior Member

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    Hi,

    Fish, You might need to reduced the load on the gearbox by reducing the prop size a bit

    Might just be too much torque when getting out of the hole.
  5. AMG, Mar 11, 2012
    #5
    AMG

    AMG YF Moderator

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    Here the Yanmar 315 diesels with Bravo3 have used the spray since many years and I think I saw it on their new V8 as well. Another reason may be when you have stainless props, which are heavy and puts pressure on the gears when shifting forth and back. We have seen it especially on Taxi Boats.
  6. Fishtigua, Mar 11, 2012
    #6
    Fishtigua

    Fishtigua Senior Member

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    When the supercharger kicks in, which is jolly nice, the prop bites really well for pick up and top end.

    I think the torque band may be a bit high for a Gas rated drive with a GKN UJ. The X drive is normally fitted to Yanmars.
  7. YachtForums, Mar 11, 2012
    #7
    YachtForums

    YachtForums Administrator

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    The go-fast group at OffshoreOnly.com will likely have some wisdom. Check out their forum on drives & lower units, located here...

    Drives and Lower Units - Offshoreonly.com
  8. Fishtigua, Mar 11, 2012
    #8
    Fishtigua

    Fishtigua Senior Member

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    Thanks Carl, I'll have a looksee.
  9. RT46, Mar 11, 2012
    #9
    RT46

    RT46 Senior Member

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    is it the GM supercharged diesel a 6.5?
    the TQ and HP are close enough on the 454 and GM 6.5 so they can handle the same transmissions, i dont know about an outdrive.




    I am a big fan of the GM 6.5, i am very suprised it never really took off as a popular small marine diesel, it is probablly the easiest swap for the 454 and has the same mounts and bell housing.....