ROTAX B GEAR BOX, 447 503 582, 8 HOLE CASE

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The model B gearbox is by far the most popular gear box from Rotax. These boxes bolt easily to any current production engines using provision 8 crankcases. If you are replacing an existing gear box, inspect the PTO end of your engine to see the crankcase type you are trying to fit. Older engines may have provision 4 or no provision to mount the gear box See the parts section for mounting of older gearboxes. All provision 4 gearboxes are still available, but require a declaration to be filed out and notarized. See rear of catalog for declaration form. Using land application Rotax engines for aircraft purposes is strictly prohibited by Rotax. The declaration is designed to prevent this practice.

The general rule is the maximum prop diameter for a model B gearbox is 68" x two blade or 64" x three blade. Anything larger and the engine will not idle smoothly below 2000 rpm or will be difficult to start. For more on the effects of prop inertia see Part #31 Measuring Prop Inertia located in the rear of this catalog. With the model B gearbox the most popular gear ratio is 2.58 (over 90%). Ratios of 2.24 to 1 and 2.0 to 1 are also available where a smaller diameter must be used. This box is always used on Rotax 277, 377, 447, and 503 engines (50 horsepower or less). If you are not sure what reduction ratio your box is simple count the number of teeth on each gear and divide the big gear by the small gear to get the ratio. Example: 49 divided by 19 = 2.58. This formula works on any gearbox.


Type b gearbox for 582

Danny D
October 4, 2019


Q: Regarding ROTAX B GEAR BOX, 447 503 582, 8 HOLE CASE: Is the ratio written on the box somewhere?

The gear ratio is stamped on the cover at the factory. Even though the ratio is stamped, that does not mean the gears have not been changed. If you're unsure the only way to know for sure is to count the gear teeth and do the math.

Q: Can I use a B gearbox on a Rotax 582?

Yes, B gearbox will work.

Q: What type of oil goes into the 8 hole B gear box on a Rotax 503?

See Part# 15-05963

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