The O.S. Engines FS-91SⅡ (Surpass Mark II) is a high-performance, discontinued four-stroke nitro glow airplane engine designed for scale, sport, and aerobatic radio-controlled aircraft. It is celebrated for its ability to spin larger propellers and generate a broad, reliable power band compared to traditional two-stroke equivalents
Displacement: 0.912 cubic inches (14.95 cc).
Bore & Stroke: 1.091 in (27.7 mm) x 0.976 in (24.8 mm).
Power Output: 1.60 hp at 11,000 RPM.
Practical RPM Range: 2,000 to 12,000 RPM.
Weight: 22.9 oz (649 g).
Carburetor: Type 60P updraft carburetor.
Fuel Mixture: Methanol-based glow fuel with at least 18% lubricant (castor oil or synthetic) and 5% to 15% nitromethane.
Glow Plug: Factory optimized for the O.S. Engines Type F glow plug, designed specifically for four-stroke cycles.
Recommended Propellers: Sport & Stunt: 11×10, 11×11, 12×9.5, 12×10, 12x11Scale: 13.5×8, 14×7, 15×6, 16×6 3-Blade: 12×8, 12.5×7
