O.S.SPEED R21-M6 M-Works Marine Racing 3.5cc Engine
This is the new 2026-edition Minicars Works O.S.SPEED R21-M6 3.5cc long-stroke competition engine.
Features:
- NEW 2026: two water cooling heads are included - std volume + a new M-Works head with larger volume!
- DLC coated & balanced R21 Euro-II crankshaft with more timing
- 9-port cylinder liner with 3-port exhaust
- Piston with 3 oil-grooves
- Ceramic main ball bearing
- Reinforced "R" conrod
- Backplate with steel thrust plate for lower friction and increased durability
- No carb included - choose your own carburetor (15mm diameter neck)
Suitable for competition boats (experience level ”high”):
- Offshore (with gear deduction)
- Endurance (with gear reduction)
- The R21-M6 is not recommended for Hydroplanes with direct drive as its too peaky for that application and the extra possible power is not needed.
Recommended fuel:
- 12% nitro fuel with 8% Klotz Benol oil (Recin) + 4% Klotz Original Techniplate (Synthetic)
- We don't recommend running the engine with less oil than the above recommended levels. You may add more recin/castor oil (Klotz Benol) in extreme conditions and heavy loads.
Performance R21-M6 vs R21-M5:
- The R21-M6 has even higher timing numbers in the crankshaft and piston liner.
- The R21-M6 has more peak power but a narrower power-band.
- The R21-M6 is the highest performance out-of-the box engine for gear-reduction applications.
- The R21-M5 is easier to set-up as it's less peaky and have more torque vs the R21-M6.
9-port sleeve with re-designed ports with improved flow for more peak power and a piston with 3 oil grooves.
Reinforced "R" connecting rod is stronger to withstand even more abuse.
The rear bearing is ceramic.
DLC coated and balanced crankshaft from the R21 Euro II engine for more power overall.
Steel insert backplate for less friction and more durability.
Two cooling heads are included - normal volume + a new M-Works head with larger volume!
Combustion chamber with smaller volume for lower nitro levels.
Specs:
- Displacement: 3.49cc
- Bore: 16.08mm
- Stroke: 17.2mm
- Crankshaft dia: 14mm
- Practical r.p.m. Range: 4.000～43.000
- Output: 2.76hp @ 35.000r.p.m.
- Weight: 265g
Included:
- O.S.Speed R21-M6 Minicars Works Marine Engine
- RP6 Glowplug
- O.S.Speed flywheel cone
- O.S.Speed decal
