Offshoreonly.com - Prop for TQ or HP for top speed???

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Re: Prop for TQ or HP for top speed???

Quote:

Originally Posted by Michael1

As far as peak horsepower, and best top speed, many of you got it correct. It is at the horsepower peak. Engine torque is one of those figures which is interesting on the dyno, but not important overall, because we have transmissions to change horsepower into drive torque. If it was important, we wouldn't have Formula 1 cars with their little 183 cu. in. engines doing 0-100 mph in 3.6 seconds.

Michael :D

Okay, if torque is not important overall. Lets build to boats to run from NYC to Key West. Identical hulls and drives in the 36ft range to take weather and other elements. We will put 500HP 540CID bulldogs in one boat and 650HP Turbo charged Chevy Ecotec 4 cylinder's in the other one. Each boat will be geared and propped accordingly to match engines max HP. Race will start with boats in neutral.

Anyone want to bet who will be sipping rum and coke at Sloppy Joe's?

Chris

Re: Prop for TQ or HP for top speed???

Thank you, I have been saying TQ for years. Perfect example above.

Re: Prop for TQ or HP for top speed???

Torque is king!

I raced my 28 Pantera in 2003 with a 540 CI motor turning 5800 RPM - Motor made 625 hp @ 5800 RPM . Turned a 26" prop - Boat 77-78 mph but took forever to get there.
Changed the cam so HP peak was now at 5000 RPM . Boat turned a 28 " prop @ 5000 RPM, midrange and acceleration were awesome . The tradeoff for the 2-3 mph in top speed was well worth it .

It comes down to hull design - Efficient hulls can use the hp to accelerate hard and run fast (cats , stepped hulls ) . Traditional deep vs' need the torque to accelerate hard and run good top speeds .
Bottom line - The boats' hull design dictates what works best . One engine recipe does not work for all !
Torque =acceleration , HP = speed