O.S. 21XM VII Outboard Marine

Engineered to take down the competition!

Take down the competition with the 21XM Version II Outboard Marine engine from O.S.! It retains many of the features found on the successful 21XM, including the 20J carburetor and #8 glow plug. New additions include efficient air cooling, a larger muffler and more!
Displacement: 0.21 cu in. (3.5 cc) Output: 1.3 hp (25,000 rpm) RPM Range: 3,000-25,000 Weight: 24 oz (682 g) Bore: 0.654 in (16.6 mm) Stroke: 0.630 in (16 mm) Requirements: Glow fuel with 10-30% nitromethane content (use 20% for break-in), Glow plug igniter, Starting belt, Shore equipment

Please note: because of the competition nature of this engine, it is not covered by the O.S. 2-year limited warranty.
Also note: this engine starts and runs in a clockwise direction at the starter cone. Any attempt to start the engine in a counter-clockwise rotation may cause serious damage to the engine. Because of the clockwise rotation, the crankshaft features reverse threads.
  • Designed expressly for small and medium-size outboard boats.
  • Cooling the head with air is more reliable than water cooling, and prevents overcooling.
  • The larger muffler boosts engine power for greater speeds.
  • Retains many of the features of the highly successful 21XM.
  • 20J carburetor.
  • Installed aluminum tilt transom mounting plate.
  • Assembled outboard unit with flexible propeller.
  • Blue anodized aluminum heat sink head.
  • 1.7 in. (42 mm) carbon fiber propeller.
  • #8 glow plug.
O.S. 21XM VII Outboard Marine - cylinder head
Cooling the cylinder head with air is more reliable than water cooling, and prevents overcooling. It also adds the benefits of simpler construction and less maintenance.
O.S. 21XM VII Outboard Marine - muffler
While being larger than the muffler used with the .21XM, the VII's muffler is still just as easy to tune, still detachable for easier maintenance, and more responsive than a tuned pipe.
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