O.S. .21XM VII Air Cooled Outboard Marine Engine w/20J Carburetor

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This is the O.S. .21XM VII Air Cooled Outboard Marine Engine. Leave it to the engineers at O.S. to concoct a sure-fire recipe for marine racing success! First, they started with the .21XM, O.S.' exceptional outboard engine and winner of 11 championships in a 4-year span. They then upgraded the cylinder head and muffler. The result: the .21XM VII, an air-cooled powerhouse that's even faster than the original!

Cooling the cylinder head with air is more reliable than water cooling, and prevents over cooling. It also adds the benefits of simplified construction and reduced maintenance. The redesigned muffler is larger than the muffler used with the .21XM, but the VII's muffler is still just as easy to tune, is detachable for easier maintenance, and is also more responsive than a tuned pipe.


  • The machined head is air-cooled, which insures optimum engine temperature under any conditions
  • The muffler has been extended to generate more torque and power
  • With perfectly matched port timing, exhaust outlets, compression ratio and carb bore, the .21XM VII is designed for competition, right out of the box
  • The 20J carburetor has both high-speed and idle needles
  • A pressure line from the muffler sends a steady flow of lubricants to the lower unit
  • Prop height and angle can be adjusted independently
  • Ball bearings minimize friction and wear for longer life and higher top-end speeds
  • The bronze prop shaft assembly offers extreme durability
  • A lightweight aluminum piston is performance-matched to a long-lasting ABN cylinder sleeve
  • An exceptional value as well as a total competitive package, complete with a #8 glow plug and 42 x 1.2 carbon prop

Displacement: 0.211 cu in (3.46 cc)
Bore: 0.654" (16.6 mm)
Stroke: 0.630" (16.0 mm)
Practical RPM: 3,000-25,000
Output: 1.3 hp @ 25,000 rpm
Weight: 24.1 oz (682 g)
Prop Shaft Diameter: 3/16 in
Requires: 10-50% nitro boat fuel with at least 18% oil content, starting equipment, fuel tubing

Includes: mount, outdrive unit, E-2050-2 removable muffler, starter cone, #20J carb, #8 glow plug, steering bracket, throttle link assembly & 42 x 1.2 carbon prop

This product was added to our catalog on July 18, 2011