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Which prop is bigger?-gctid405936

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    #1

    Which prop is bigger?-gctid405936

    I have a 1996 2252 hardtop with a 5.7 Mercruiser with an Alpha 1 gen 2.

    Previous owner had the engine rebuilt and it had 25hours when I bought it. It currently has 55hours.

    Im trying to figure out why Im not getting good mileage or performance.

    On a 60 mile roundtrip a month ago I calculated about 1.5 mpg cruising at about 30mph, which I think was about 3200rpm. (topped off before going out and again afterwards, so I knew my quantity of fuel burned). I also top out at 35mph, alone.

    This weekend I noticed fuel dribbling in the carb throat when idling so I switched the link position on the accelerator pump arm link and that got rid of the dribbling, got rid of my hard starts when cold, but now I only top out at 32mph.

    Not much info related to these specific boats can be found, but on one boat test they were able to do 40mph, with the v6. So i expect better than that.

    Anyway, to my question.

    Current prop appears to be a 15.25 by 15p (cast in so it is not to legible) with a 2008 and other markings. Quicksilver lists a 2008 partnumber as a 15.5 by 15p.

    The Bayliner parts website lists a 14.5 by 17p prop as standard equipment.

    Is the 15.25 by 15p a "bigger" prop than the 14.5 by 17p?

    Is the pitch the distance to complete one turn?
    Tags: None
    #2
    green650 wrote:
    Anyway, to my question.Current prop appears to be a 15.25 by 15p (cast in so it is not to legible) with a 2008 and other markings. Quicksilver lists a 2008 partnumber as a 15.5 by 15p.The Bayliner parts website lists a 14.5 by 17p prop as standard equipment.Is the 15.25 by 15p a "bigger" prop than the 14.5 by 17p?Is the pitch the distance to complete one turn?
    15.25 inches in diameter and it travels 15 inches in the water in one revolutionverses14.5 in diameter travelling 17 inches in the water for one revolution

    http://baylinerownersclub.org/media/...0BMW.jpg[/img]
    Boatless at this time

    A veteran is someone who, at one point in their life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including their life."

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      #3
      That is what I thought.

      So since the diameter is not too different, it seems like my current prop is more aggresive?

      Could that account for poor mileage/lack of top speed/unability to go past 4000rpm?

      Comment

        #4
        You should be able to get within 200 rpm of WOT (wide open throttle)

        2850Bounty might chime in but it sounds like you have too big a diameter prop.

        I have found the best thing to do is contact a local prop shop. (not westmarine but an actual prop shop)

        Tell them what sized prop you have, size engine, outdrive and the RPM's you are reaching. They can usually dial you in with the right prop first shot.

        In my outboards case they hooked me up with a smaller diameter, deeper pitch 4 bladed prop that worked great.
        Boatless at this time

        A veteran is someone who, at one point in their life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including their life."

        Comment

          #5
          Good bunch of general prop info here:

          Page not found
          http://www.go2marine.com/docs/mfr/michiganwheel/mercruisersd.shtml

          Comment

            #6
            What did you change on the carb exactly? When people start messing with carbs, things usually go South really fast.

            What is your RPM at full throttle?

            Comment

              #7
              Full throttle was 4200 rpm.

              Now it is 4000rpm.

              I changed the hole that the accelerator pump lever was attached to. Raw fuel was dribbling into the carb so I thought maybe it was "accelerating" too soon?

              Raw fuel is no longer dribbling in the carb, so it seemed to cure that problem.

              It is also made it easier to start. Before, it would start, idle, than die. Kind of like it was short on fuel.

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