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new inboard gph?

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  • new inboard gph?

    Wondering if you guys could tell me if your gas mileage sucked when your motor was getting broken in? I have 6 hours on a new inboard and i'm not getting the advertised gph. Any other tips on break-in would be helpful also. Thanks!


  • #2
    Boat, engine, pump? What are you burning now? What did they advertise?


    • #3
      Fuel Burn

      You'll soon find most boat owners and builders tend to tell tall tales on how great their boat is on fuel efficiency. A 270 hp gas engine will burn ~15 gph at 3/4 throttle. Best instrument I have on board is a Floscan tied into the GPS to monitor fuel burn, and give me an accurate reading on how much gas I have left - my fuel gauge is worthless.


      • #4
        boat info

        it's a 20' Phantom Sportjohn w/ 175hp Mercury Sportjet. I keep it around 3800 rpm like I was told, supposed to get around 6 gph, I don't have exact numbers on gph but i'm thinking it's only getting about 9-10 gph. Hope that gives you more info. Other than that I love the boat, it really does run super shallow once you get the hang of it. Thanks guys!



        • #5

          How much stuff you have in the boat will dramatically affect your fuel usage too. Also, how you load the gear and people can cause problems too. Go light and well balanced for best mileage.


          • #6

            I'm sure you've been told this but pay attention to:
            -Don't run WOT (Wide Open Throttle) for very long at all (<1 min.) during break-in and not much more than 3/4 of WOT for cruise speed.
            -Don't run at one consistant speed during the first 50 hours. (No trolling or cruising!)
            I'm not sure what you can expect out of that little 175 Mercruiser but 10 gph at 3800 rpm sounds about right. A FloScan is a good investment.
            I'm using a 260 hp Chrysler (360 cid) to push a 24' 5000# boat for 11 gph at 2900 rpm. My WOT is 3800 rpm and it burns about 26 gph if I push it up there.


            • #7
              Get a'll never use those worthless fuel guages again and it makes fuel management much, much easier!!!! It is extremely difficult to obtain accurate GPH figures by just using the guages.


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