Ace Electronics

Thunder Tiger - Pro 21M Outboard

Pro 21M Outboard Marine Engine

Product No. 9567

A race-proven PRO-21M power head is mated to a lower unit that utilizes the best aspects of gear and flex-cable drive technology. A innovative design that is sure to increase the popularity of the 3.5cc Tunnel Hull class.

A special set of precision helical gears transfers power from the crankshaft to the flex-cable, resulting in substantially reduced cable wear and maintenance, while the integrated expasion chamber (muffler) reduces exhaust noise.

The Marine series are manufactured by automated computer-controlled machinery, resulting in a product that looks and performs better. The engine mount allows adjusment to both propeller depth and angle with a Prather S215 propeller which is included. Precision air bleed carburetor makes adjustments simple.

A Closer Look


  • Top grade CNC equipment, state-of-the-art technology are used.
  • Improved quality; ISO9001 Certified which guarantees the maximum power and performance.
  • Gear drive / flex cable.
  • Prather S215 propeller which is included.
  • Adjustable prop depth and running angle.
  • Air bleed carburetor makes adjustments simple.
  • Economic marine engine for the serious boat racer.


  • Fuel with at least 20% lubricant with 5-15% nitro content, fuels containing a blend of both castor and synthetic oils are best
  • R/C long type glow plug such as the O.S. #8
  • Glow starter
  • Shore equipment


  • Displacement: 0.211 cu in (3.46 cc)
  • Bore: 0.654 in (16.6 mm)
  • Stroke: 0.630 in (16.0 mm)
  • Practical RPM: 3,000 - 38,000
  • Output: 2.10 hp @ 30,000 RPM
  • Weight: 25.39 oz (720 g)
  • Gear Ratio: 1.19:1

Also Available

Description: Pro 21M Outboard w/1.04:1 gear ratio Product No.: 9568