Marine thermal engine O.S. 21 VZ-M - 3.49 cm3

O.S. MAX 21 VZ-M 

The O.S. MAX 21 VZ-M represents one of the most powerful engines ever developed by O.S. Engines for model boating.

Designed for radio-controlled speed boats, this 2-stroke glow engine of 3.49 cm³ (.21 cu.in.) combines exceptional power, impeccable manufacturing quality, and proven reliability in the world of competition.

The 21 VZ-M, the result of several decades of experience from the Japanese manufacturer, was developed to meet the expectations of pilots looking for an engine capable of providing sharp accelerations, extremely rapid revving, and perfect stability at very high speeds.

Thanks to its water cooling and optimized design, it maintains consistent performance even during the most intensive uses.

Competition-Worthy Performance

The MAX 21 VZ-M has a displacement of 3.49 cm³ and delivers an impressive power of 2.75 hp at 33,000 rpm.

Its operating range extends from 4,000 to 45,000 rpm, making it particularly suitable for RC boats designed for pure speed.

Technical Specifications

• Displacement: 3.49 cm³ (.21 cu.in.)
• Bore: 16.27 mm
• Stroke: 16.80 mm
• Power: 2.75 hp at 33,000 rpm
• Operating Range: 4,000 to 45,000 rpm
• Weight: 307.5 g

These performance capabilities allow the engine to respond immediately to demands while maintaining excellent operational consistency.

High-End Design by O.S. Engines

The 21 VZ-M features an architecture specifically developed for high-performance marine engines.

It includes:

• a water cooling system ensuring excellent temperature control;
• a Turbo head compatible with high-performance Turbo glow plugs;
• a 21D carburetor with a large diameter for consistent fuel delivery at very high speeds;
• precision machining ensuring excellent sealing and durability.

This level of craftsmanship allows the engine to maintain its full power while remaining highly reliable when properly maintained.

An Engine Designed for Radio-Controlled Speed Boats

The O.S. MAX 21 VZ-M is primarily aimed at enthusiasts of competitive nitro RC boats as well as modelers looking to equip a high-performance hull with a top-tier engine.

Its significant power, high torque, and ability to reach very high speeds allow for full utilization of modern speed boats' potential while maintaining excellent operational stability.

It also serves as an excellent choice for restoring iconic models equipped with original O.S. engines.

Accessories supplied with the engine

Unlike several older marine engines from the brand, the flywheel is well supplied as standard with the O.S. MAX 21 VZ-M.

However, the exhaust manifold/header is not supplied by O.S. Engines. If your setup requires this component, it will need to be purchased separately.

This clarification is important, as some photographs may show the engine equipped with optional accessories that were not part of the original equipment.

Why choose an O.S. MAX 21 VZ-M engine?

The 21 VZ-M perfectly illustrates the expertise of O.S. Engines, a globally recognized brand for the quality of its model engines.

Even today, it remains highly sought after by model ship enthusiasts for its high power, quality machining, reliability, and remarkable performance.

Whether for competition, restoring an RC boat, or enhancing a collection, the O.S. MAX 21 VZ-M remains one of the most iconic marine glow engines from the Japanese brand.