I recently purchased a 1999, 20ft Viper, Cobra. Had a 2009 Yamaha 250 Vmax, series 2. Upon test driving, the boat attained a speed of 70 mph (gps) in choppy water, with no chinning at 70. The boat has a hydraulic jack plate, setting the motor back 6"s from transom. When maxing out speed during...
