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Mercury 9.8HP power question

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  • Mercury 9.8HP power question

    I have the following setup with a Mercury 9.8HP pushing it. This boat has a 350lb guy in the rear, a 225lb guy up front, a cooler with a couple 6 packs and a tackle box and 4 rods.





    My question is should I expect this setup to go faster than 7MPH in smooth water? This is the max speed that I can get out of it at full throttle and I usually run about 3/4 throttle. No idea about props or anything like that so I am not sure if the prop is one that someone threw on or if it is the correct one for this engine.



    Also, can anyone tell me what I would patch a couple of cracks towards the rear of the bottom of this boat? Not too bad, just letting in a bit of water.

  • #2
    Re: Mercury 9.8HP power question

    that motor looks to be a long shaft... if you had a short shaft on there, the props higher out of the water, and it should give you some more speed.. if you dont want to get rid of that motor, i am out of ideas. hopefully someone else can help you farther
    fishinhardwater

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    • #3
      Re: Mercury 9.8HP power question

      oh almost forgot... another thing to metion is maybe try to raise your engine up higher somehow.. i recall seeing other boats have a plate called a "hi-jacker" which raises their engines up. Good luck
      fishinhardwater

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      • #4
        Re: Mercury 9.8HP power question

        That's a lot of weight in that small (good looking) boat, but I think you should be able to get her on plane with a 9.8. That should be about 10-15 knots.

        Check out what FHW says. The AV plate should be even with or very slightly above the level of the bottom. You might also move some weight aft to get her on plane.

        Good luck.
        sigpic

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        • #5
          Re: Mercury 9.8HP power question

          Originally posted by JB View Post
          The AV plate should be even with or very slightly above the level of the bottom. You might also move some weight aft to get her on plane.
          Sorry, whats an AV plate? Also, I am afraid if I add any more weight to the rear, water might come inside with my big 'ol butt sitting back there steering. Not sure how to tell if the boat is 'on plane'. I am new to boating and still learning what's what.

          Also, did anyone see the last bit about the bottom leaking a bit? Just curious if anyone had similar problems and could tell me how to repair it.

          I am also looking locally for someone that might be getting rid of a larger aluminum shell that I might use to replace the smaller fiberglass one because I figured I was putting too much weight in it.

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          • #6
            Re: Mercury 9.8HP power question

            The anti-ventilation (AV) plate is the horizontal plate just above the prop, SB.

            You know, you just might be over the weight limit of that boat. What does it say about weight/passengers on the capacity plate?
            sigpic

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            • #7
              Re: Mercury 9.8HP power question

              Originally posted by JB View Post
              The anti-ventilation (AV) plate is the horizontal plate just above the prop, SB.

              You know, you just might be over the weight limit of that boat. What does it say about weight/passengers on the capacity plate?
              Thanks. I will see what I can do about raising the engine up a bit.

              I have not found a capacity plate yet, I think the PO must have removed it for one reason or another. I will be pulling the carpet soon and maybe I will find it under there somewhere.

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              • #8
                Re: Mercury 9.8HP power question

                If I were to use high quality hardware and wood, would there be an issue other than watching for rot building a jack plate to raise the engine 4-6 inches out of wood instead of buying an aluminum?

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                • #9
                  Re: Mercury 9.8HP power question

                  What would you guess the rpm is?. My 9.8 on a 14"boat and a 7 pitch prop goes 17 mph.With a higher pitch,(9) all my boat did was bog and push water.It would not plane.A lower pitch prop will raise rpm.The pitch number is stamped into the prop usually with the part #

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                  • #10
                    Re: Mercury 9.8HP power question

                    Originally posted by rainbro View Post
                    What would you guess the rpm is?
                    I have no way to even estimate that. This is my first outboard and boat so I am learning as I go.

                    Originally posted by rainbro View Post
                    My 9.8 on a 14"boat and a 7 pitch prop goes 17 mph.With a higher pitch,(9) all my boat did was bog and push water.It would not plane.A lower pitch prop will raise rpm.The pitch number is stamped into the prop usually with the part #
                    I will look tomorrow, it is at my brother's house waiting for my rewind spring to come in so we can put it in.

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                    • #11
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                      Re: Mercury 9.8HP power question

                      Originally posted by rainbro View Post
                      The pitch number is stamped into the prop usually with the part #
                      The numbers on my prop are:

                      30431F

                      7P A1

                      I would assume that would be a 7 pitch??? Also, I looked at the engine mount and the AV plate is just a small amount higher than the bottom of the boat (less than an inch). I guess with as much weight as I have in the boat, I am stuck at 7 MPH. Might get the local marine repair shop to look at the engine to ensure that it is operating as it should.

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