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Under Drive Pulleys

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Old 02-09-2003, 05:04 PM
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Default Under Drive Pulleys

What does everyone think of Under Drive pulleys that slow down your accessories? If I put these on the boat, I will put a crossover water tube on it, so cooling water isnt an issue.

Thanks for any info,
Tommy
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Old 02-09-2003, 05:25 PM
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It plays movies!!! Now all i gotta do is figure out how to hook it up to cable, then reciever, then tv...... Thanks

They claim 15hp....I know that 1lb off the rotating assy. is 2.7hp.
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Old 02-09-2003, 06:00 PM
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Don't bother Hyper you will not see a difference. You need a lot more to see any gain in speed on a boat. If you are dead set on it then SAVE your money I have some pulleys that I tried on my boat to see zero gain and I would be happy to send them out to you so you can experiment with them and learn by doing if you want to. Otherwise I would say save your money.

Jon
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Old 02-09-2003, 06:10 PM
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You would never see a difference. Remember horsepower is acceleration, torque is top speed. The load difference with underdrive pulleys allow a little better acceleration but doesn't lower the "gear ratio" enough to reduce the torque load noticeably. TNSTAAFL dude! Theres No Such Thing As A Free Lunch!
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Old 02-09-2003, 06:39 PM
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-i have tried: no difference

go4broke:hp for acceleration,torque for top speed ? i knew the opposite... which of us is right? I am confused
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Old 02-09-2003, 06:42 PM
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Yeah, i thought it was the opposite?

Thanks guys, you save me 100$
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Old 02-09-2003, 07:08 PM
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I hate to do it...... but...... I am going to have to agree with timcin, as a result of me having to do that I must now go have a drink
 
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Old 02-09-2003, 07:20 PM
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LOL
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Old 02-09-2003, 07:28 PM
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Horsepower is work done over time. thats how fast you go 0 to 100. In drag racing your trap speed (top speed) can be used to figure your horsepower but that is on a track of a certian length, therefore making an average rate of acceleration to use to figure the work (horsepower) done. The vehicles top speed has nothing to do with its acceleration.
Torque is the strength of the engine, it takes x amount of ftlbs of torque to turn the prop and outdrive gears at the rpm necesary for top speed, its basicly a dyno pull. Dyno's measure torque and calculate horsepower. The bigger the prop, the more speed at a given RPM, the more torque required to turn it.
Look at the diesel powered performance boats that have been experimented with, no hp for accelerating, but still post high topend numbers due to massive torque, they can swing props way too big for a gas motor with the same hp, but less torque. There are also rpm differences between gas and diesel that factor in, but I don't want to make a too complicated example.

A boat that runs 100mph top end but takes 2 hours to get there at WOT would have low horsepower but high torque.
I hope this rambling post isn't too confusing, I think I'll join Packin for a drink.
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