Although you need both, the saying I've always found true is that "Torque tows and horsepower hauls ass." Of course as has already been said, where in the RPM band a boat makes lots of either is critically important. Torque down low will get you on plane quicker. Lots of horsepower - all at 6,000 RPMs - will get you nowhere.

You need enough low RPM torque to get the boat going fast enough to achieve the maximum horsepower RPM.

Here is a great post regarding this from the OSO archives -

http://www.offshoreonly.com/forums/g...l-speed-2.html