O.S. reliability and output - in a .21-sized outboard
The 21XM represents a first from O.S. - a high performance outboard power plant, with features that the serious boat racer will appreciate. Some of its incredible features include Schnuerle-porting, multiple bearings and a lubrication system for the flex shaft bearings for greater performance and increased longevity. The engine's height and angle are adjustable to further optimize performance Comes with a detachable muffler, for easier installation of tuned pipes  Also includes a high performance Type 20J carburettor, water pickup, flexible driveshaft and a high performance ready to race right out of the box

With more and more 'outboard' style boats becoming available O.S. have developed an engine to take the market by a storm! Its robust cast construction with integral silencer box has been mated to a purpose designed, high performance engine to provide blistering speed as well as rapid acceleration. If you're going to race outboards then race the best, the new O.S. MAX 21XM!

Specification
Displacement:  3.46cc ( 0.211cu. In.)
Bore:  16.6mm (0.654in.)
Stroke:  16.0mm (0.630in)
Power Output:  1.3ps/25,000r.p.m.
Practical RPM:  3,000-25,000r.p.m.
Weight:  670g (23.6oz.)