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Are today's 4-strokes more powerful than the old 2-strokes?
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<blockquote data-quote="onthewater102" data-source="post: 380866" data-attributes="member: 13702"><p>You were right on the money with the different rating standards over time - an older motor with its power rating based on a measurement at the flywheel will not have the same power as a modern motor measured at the prop. </p><p></p><p>HP is the amount of energy needed to accelerate 550lbs 1ft/sec, usually computed by the formulas [torque (in ft/lbs) * RPM]/5252 or wattage/746. When comparing old engines to newer ones the RPM speed at which the HP rating is taken is very important as it skews where you will experience the full power of the motor. My 1955 5.5hp isn't much, but it's rated at 4200 rpm vs. newer motors that are rated at 5k plus, so I have a lot more torque at lower engine rotation peeds with that than I would get out of a comparable modern motor which would need to be wound up to produce similar power. The difference is the greater torque will allow the engine to accelerate heavier loads faster than a less torquey motor that has to build up speed in order to generate more power.</p></blockquote><p></p>
[QUOTE="onthewater102, post: 380866, member: 13702"] You were right on the money with the different rating standards over time - an older motor with its power rating based on a measurement at the flywheel will not have the same power as a modern motor measured at the prop. HP is the amount of energy needed to accelerate 550lbs 1ft/sec, usually computed by the formulas [torque (in ft/lbs) * RPM]/5252 or wattage/746. When comparing old engines to newer ones the RPM speed at which the HP rating is taken is very important as it skews where you will experience the full power of the motor. My 1955 5.5hp isn't much, but it's rated at 4200 rpm vs. newer motors that are rated at 5k plus, so I have a lot more torque at lower engine rotation peeds with that than I would get out of a comparable modern motor which would need to be wound up to produce similar power. The difference is the greater torque will allow the engine to accelerate heavier loads faster than a less torquey motor that has to build up speed in order to generate more power. [/QUOTE]
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Are today's 4-strokes more powerful than the old 2-strokes?
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