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ENGINE rpmS AND PROP SIZE-gctid384600

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    ENGINE rpmS AND PROP SIZE-gctid384600

    I recently purchased a 1985 Bayliner 2850 Contessa Command Bridge. The engine is GM/Volvo Penta, Aquamatic 280 I believe. Was not used much. Took it out had a little difficulty getting up on plane. Tach was about 3000RPMs. Unsure what size prop is on it. Engine seems to run smooth, was a little rough at first, but fuel treatment seemed to correct that. My questions are as follows; What is the max or suggested RPMs numbers for this boat and what prop size should I be using. Any information would be greatly appreciated.
    Raymond 14
    1997 3388ES
    twin merc 350 inboards

    #2
    Congrats on your purchase.

    Also post pics when you get a chance. What size engine.

    Add your information in the signature.

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      #3
      If it's a single its a 260 (350 ci). This engine is not known to be real peppy for our size boat so don't expect a hotrod. The 2850 is a lot of boat for a sngle 260. Yes it should be a AQ280 sterndrive.

      I have twin 225s (305 ci) in mine, so I cant give you much in the line of comparison. You got a great boat, one of my favorite in the older Bayliners. Mine was very rough when I got her, but cleaned her up and I LOVE my boat.

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        #4
        Welcome to the BOC, Ray.

        Raymond14 wrote:
        I recently purchased a 1985 Bayliner 2850 Contessa Command Bridge. The engine is GM/Volvo Penta, Aquamatic 280 I believe. Was not used much. Took it out had a little difficulty getting up on plane. Tach was about 3000RPMs. Unsure what size prop is on it. Engine seems to run smooth, was a little rough at first, but fuel treatment seemed to correct that. My questions are as follows; What is the max or suggested RPMs numbers for this boat and what prop size should I be using. Any information would be greatly appreciated.
        I've worked on many of these over the years, and in your year range, of which means these were Volvo Penta. These boats with the single prop drive struggle to get on plane..... no matter which single propellers you try.

        Unfortunately, the cure is a rather expensive one, but well worth it if the cost can be fit into your budget.



        Many BOC members have done the DP addition, and are having great results.

        Often we'll realize better performance than if we went to an engine with more horse power.

        As for propping (whether Duo Prop or Single Prop), you will have a specified WOT (wide open throttle) RPM that the engine must meet.

        When propped correctly, your particular SBC 5.7L engine will reach 4,400 to 4,600 RPM (revolutionS per minute).

        NOTE: this is a testing RPM..... not an RPM to be sustained!

        Check the bottom condition for marine growth, etc, and test several props and see if you find one that offers you the OEM specified WOT RPM.

        *************************

        You should like this boat. There are several members who have this model.

        Our member Mike C (aka Gilligan) just purchased a 2850 CB similar to yours. His is equipped with the Duo Prop.

        I think that Mike will have some photos for us soon.

        http://"http://baylinerownersclub.or...s photo album.
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

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