A pair of Caterpillar 3406B turbo charged diesel engines were converted to operate in a dual fuel mode installed in a small vehicle and passenger ferry and evaluated for performance for both diesel and natural gas operation. Full load power was achieved with dual fueling without knock. The “life” of the engines was extended from 15,000 marine hours to 30,000 marine hours (120,000 miles). This is equivalent to 600,000 miles and 1,200,000 miles in a road or truck application. Piston, piston rings, valve and bearing wear, was found to be significantly reduced and CO2 concentrations in the exhaust were also minimized. Lubricating oil life was also extended.