Johnson Evinrude OMC Engine Tuner Johnson Evinrude Engine Tuner is recommended to maintain full power and efficiency in outboard motors, marine engines, power tools, snowmobiles, and other internal combustion 2- and 4-cycle engines. For use in engine tune-up to remove gum and varnish build-up, excessive carbon deposits from rings, pistons, valves and ports. Spray through air intake of 2 and 4 cycle engines for improved performance. Treatment is recommended every 50 hours or at least once a year.