Can the alpha drive handle over 300hp?

Discussion in 'Boatbuilding' started by Dustin, May 21, 2006.

  1. Dustin
    Joined: May 2006
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    Location: Utah

    Dustin New Member

    How often does Merc put a 5.0L with an Alpha drive? I am upgrading my motor to a 5.7L. My buddy Mat brought to my attention that the alpha might have a little trouble with the power of a 5.7L. My 5.0 has 220hp, this new motor has 315, I looked up on the Merc site that the max hp an alpha could have is 300hp. How do I tell if i have an alpha or a bravo drive...?? They look very similar. I saw on a few posts that had a number of 5.7L with the Alpha drive, is the 15 extra hp over the max on an alpha drive going to make a difference, or will it really tear the crap out of it? Any info or opinion will help, thanks
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The Alpha drive is the standard setup for small blocks(5.0/5.7). The Bravo is really different. It is about 50% bigger and it says Bravo on the side. There are three types: I, II and III.
  3. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    The Alpha can handle a 5.7 for a few seasons, even indefinitely if your boat is light and your driving sedate, but in most applications its lifespan is greatly reduced by the more powerful motor. It was really meant for the smaller engines- the 3.0, 4.3 and the 5.0. It's not the horsepower rating that matters, so much as the peak torque. The larger V-8 motors can put out a lot of torque at lower speeds, which puts a lot of stress on the driveshafts and their bearings. A Bravo is a lot heavier and harder to turn over, which is why it's not seen with the smaller motors and boats, but it is also much more durable and can handle 315 hp (or in some cases even 500+ hp) with ease.
    BTW, the Merc standard lineup:
    Alpha (for small runabouts to 300hp)
    Bravo 1 (for bigger, faster runabouts and performance craft)
    Bravo 2 (for heavy cruisers, takes up to a 20" dia. prop)
    Bravo 3 (counter-rotating props, gives a very manoeuverable and stable drivetrain)
    Bravo 1,3 XR (for high-performance boats)
    Most of the rest of Merc's line is intended for specific high-speed applications.

    Dustin, I checked back and saw you have a 19' runabout.... most likely it has an Alpha and is a fairly light boat. Since the current drive is probably an '03 like the boat, it's probably okay with the 5.7 in this case. Merc does offer the 5.7 with an Alpha but their documentation recommends a Bravo in most cases.
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