We were all surprised, however, that loading the boat to its capacity not only failed to have a dramatic outcome on its top speed, but at one point actually had a positive effect. At our baseline of 800 pounds, the Sundeck topped out at 39.98 mph. At 1,200 pounds, the boat lost nearly a full mile per hour, dropping to 39.01 mph. The effect of another 400 pounds was less dramatic, losing only about 0.5 mph, with the boat doing 38.50 mph. Adding the last 400 pounds, to bring our weight up to the max load of 2,000 pounds, made us triple check the GPS. To our amazement it increased our speed just over a mile per hour to 39.66 mph.