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150hp on a 140hp max boat

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  • 150hp on a 140hp max boat

    Ok so I’ve found a good deal on a 150hp Johnson. But my boat stamp on my boat says 140hp max. I’m wondering if it’s ok to go 10 over. The stamp is for the weight correct? This Johnson is a gt motor. It’s supposed to weight the same as a 140. Anyone have any insight on this?

  • #2
    The rating is a bit of a problem.-----I do not believe it is a hard concrete fact.------It does not account for a heavy 4 stroke motor.-----Nor does it consider crankshaft power or propshaft power.---Nor does it account for decal horsepower.------The GT 150 may well be a 165 / 170 HP motor.---Perhaps ask the local authority how they deal with thiis.----Or your local insurance provider.

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    • #3
      Originally posted by BoPaesch View Post
      Ok so I’ve found a good deal on a 150hp Johnson. But my boat stamp on my boat says 140hp max. I’m wondering if it’s ok to go 10 over. The stamp is for the weight correct? This Johnson is a gt motor. It’s supposed to weight the same as a 140. Anyone have any insight on this?
      There are Crossflow 140s, and Looper 140s, and then there are the Crossflow 150s, and the Looper 150s, all weigh differently, and as Racer mentioned, there are crank ratings and prop ratings.

      What year is the engine? What is the Boat?

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      • #4
        Why would that weigh the same as a 140? The 140 will have 4 cylinders and the 150 has 6. How about you just get the right motor for your boat.

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        • #5
          The 140 loopers are bigger and heavier than the 140 crossflow.-----The 140 looper and a V-6 crossflow are very near identical in weight and within 15 / 20 lbs difference.

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          • #6
            15-20 lbs difference is not near Identical.

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            • #7
              I ran 19 years with a 130 V4 Yamaha on a boat rated for 115 Max. Why? Both the 115 and 130 Yamaha's were the same motor. Was the 130 Heavy on the back? Yes, but no heavier than a 115 would have been, and lighter than a 115hp 4 Stroke of it's time. A high Cupped prop helped, and proper weight distribution was needed.

              2017, I wanted to upgrade, an 18' boat in either brand I was shopping, had a Max Rating of 115 hp. Price difference between a 115 and a 140hp Suzuki was only $500, and the 140 was lighter than the 115, again, same motors, but different lighter mounts on the 140. A 115 and a 150 Yamaha had a big price, weight and torque jump, so did the Suzuki. $3500, and 70 n/m of Torque and 40-50 lbs. So because the Boat had Lifetime warranty, I went 1 size larger boat 20' rated for a 150 hp, and a 140 motor.

              Torque and Weight is what will stress your transom/boat, not an extra 2-3 mph at WOT. Therefor a 140 Suzuki, lighter than a 115 Suzuki, with only 1 N/M more torque, would probably have been easier on the 18' than a 115 hp Max Rating, had there not been a Lifetime Warranty. But a Bigger Bore, Heavier, 70 N/M more Torque 150 would have been too much. The 150 being basically the same motor as a 200 hp Suzuki.

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              • #8
                Well 15 or 20 lbs on a 350 lb unit is not worth arguing about.------Boating rules / guide lines / ratings need to be updated for the market today.----They are more that 50 years out of date and not well understood by even some official agencies I would say.

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                • #9
                  Many talk about wieght when we talk HP. It's more than weight to consider. But I wouldn't lose any sleep over 10 HP until the Coast Gaurd or whomever pulled me over. A nut case I know has a StarCraft rated for 125 or so, he stuck a 150 on it. Now it leaks like a sieve. He's slamming 4 to 6 footers on Lake Erie going 50 not 30. He's nuts and one day is going to split the hull down the middle. He is down to boating solo.

                  Will the boat explode with an extra 10 HP pushing her, no it won't. If that 150 is heavier than the 140 you have lost your 10 HP so why bother.
                  Experience is a lifetime of mistakes, wisdom is not making them again.

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                  • #10
                    The driver controls how much HP is being used.
                    If I were to do what you are prosing, which I wouldn't automatically rule out, I would take the 150 decals off the motor.

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                    • #11
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                      Bo peap may not be here anymore. You still here Bo Peasch? Didn't think so, 24 posts. FOI, our info.10HP isn't 10% of a 140. If of the same make often the difference of 10 HP may be the identical engine with a up in combustion or making the displacement a tad larger. Use the old cowl. The authorities have caught onto changed decals on a cowl.
                      Experience is a lifetime of mistakes, wisdom is not making them again.

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