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1987 ciera2555-gctid394960

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    1987 ciera2555-gctid394960

    could someone please tell me what rpm i should be achieving with a rebuilt chevy 350 on this project boat?

    #2
    A typical WOT RPM for the basic 5.7L SBC Marine will be in the range of 4.2k to 4.6k RPM.

    As you may know, this is not a operating RPM..... this is a test RPM to check gearing and correct prop selection.

    .
    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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      #3
      what do you estimate rpm should be during operation?

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        #4
        4400 to 4800 RPM at full throttle with your normal load. Typically you want to tune it for hitting the top of the range with a light load and bottom with a full load. The most efficient cruise speed for most V8 motors in boats is right around 3800 RPM.

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          #5
          with a light load i am only reaching 38krpm with a 15x17 prop what should i be checking to raise this rpm?

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            #6
            That's way too low, and the prop actually seems about right for that size boat. So the things to check:

            Is the hull clean? I mean REALLY clean, no fouling?

            Check state of tune; timing, carb adjustments, etc.

            Is the prop dinged or bent at all? Even tiny bends kill speed.

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              #7
              boat has newly rebuilt carb,new electronic ignition conversion, timing is set at 10btdc, bottom is freshly scraped and painted however, outdrive is used is it possible the gearing is wrong?(OMC cobra)any suggestions?

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                #8
                That is certainly possible, but I'm not familiar with OMC at all nor have I dealt with changing gearing. You do have to fix this though, or you will damage the engine. Hopefully the OMC people will drop in with gearing advice.

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