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Rotax 185



The Rotax 185 is a 9 hp (7 kW), single cylinder, two-stroke, direct drive, industrial engine, built by Rotax of Austria for use in fire fighting water pumps that has also been adapted as an aircraft engine for use in ultralight aircraft.

The Rotax 185 was adopted as a replacement for the 5.5 hp (4 kW) Pioneer chainsaw engines used on the early Series I Ultraflight Lazairs. The 185 provides enough power to allow the Lazair to be flown on floats. Due to its design purpose as a water pump engine it proved reliable enough for use on ultralight aircraft.

In the Lazair application the 185 was used to drive two propellers stacked together in biplane configuration. This was not done for aerodynamic reasons but rather because the Lazair manufacturer had ample quantities of the nylon propellers on hand for its earlier engines and stacking them was more cost efficient than scrapping them and buying new propellers.

The Rotax 185 is no longer supported by Rotax as the rights to the design were sold to the Wildfire Group who use the engine in their Mark 3 High Pressure Centrifugal Fire Pump.


Type: two-stroke air-cooled engine
Bore: 2.441 in (62 mm)
Stroke: 2.4 in (61 mm)
Displacement: 185 cc (28.7 cu in)
Valvetrain: piston ports
Fuel system: Tillotson pneumatic pump carburettor
Fuel type: regular autofuel
Oil system: premixed in the fuel at 40:1
Cooling system: free air
Reduction gear: Custom made belt drive reduction units have been employed
Power output: 9 hp (7 kW) at 5000 rpm
Fuel consumption: 4 l/hr (1 US gph)







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