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Thread: Classic 18 Prop Question

  1. #1
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    Classic 18 Prop Question

    I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
    the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.

  2. #2
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    Try a 23" Merc cleaver. ( three blade ) I do like it on my 18. Expect to see about a 5000-5100 WOT with that and a light boat ( load ) Everyone here seems to have a favorite of their own liking due to preferred ride characteristics, etc.

  3. #3
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    Quote Originally Posted by John Grinder View Post
    I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
    the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.

    For a deep drive like yours I would borrow and try a Mercury Rev4. It's a through hub 4 blade which you can get with PVS vents which I would suggest as an option.
    1972 16 OB - C16B-63 - "Surface Tension" Resto Project
    1974 16 OB - DMR16106017-B - "The Mule"

  4. #4
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    The Rev 4 works great on my 22

    Quote Originally Posted by Greg Guimond View Post
    For a deep drive like yours I would borrow and try a Mercury Rev4. It's a through hub 4 blade which you can get with PVS vents which I would suggest as an option.
    I run a 25p Rev 4. Vary stable, 4mph faster mid range than a 3 blade and only 1 mph slower at wot.
    I'd suggest trying a 23p Turbo 1 3 blade and 23p Merc Rev 4 4 blade.
    Thanks, Patrick


    1996 22' Classic

  5. #5
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    classic 18 Prop Question

    Quote Originally Posted by John Grinder View Post
    I recently bought a 2005 Classic 18. Mercruiser 5.7L 300hp, Alpha One stern drive. At 5000 rpm I am going 60mph. At full throttle I am approaching 5400 and 65mph. I do not want to run over the red line of 5200, but I would like to be able to operate at full throttle with maximum speed.
    the prop is a 3 blade stainless. The only markings on the prop are the numbers 9170 and 21. There are no manufacturer markings I can locate. I don't want to invest in a new prop of higher pitch without some confidence with what I am doing. Any advice you could offer would be appreciated.
    Lenny, is this the Merc Mirage line of props?

  6. #6
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    I have one season on my new to me 2004 18 350 MAG/MPI Alpha.

    I haven't experimented w/ props at all, but my boat has a 23" Mirage Plus which seems like a great all rounder.

    Good for low 60s (63-ish on GPS, speedo read higher) at 5000 rpms with no bad habits.

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