We use Hurth gears for our rotary marine engines. The gears that are rated
 for our engines (175 hp at 6250 rpm) weigh 58 lbs dry, and cost over $2000.
 There are smaller, lighter, and cheaper gears on the market, but I don't
 think they can handle the speed or the torque of a 13b -- we are always on
 the lookout, so I'm interested also!
 Jon Lauter
 Rotary Power Marine Corporation

Is that a spur gear set Jon?
Paul Lamar

Bulent Aliev wrote:

Marine transmissions have reverse gear also, which complicates the design
and adds extra weight. I don't know of a marine transmissions with forward
only. Couple of years ago I was on this path of thinking and gave up.

Don Dunbar wrote
We buy many types of marine gear boxes. They can be purchased with almost any ratio for a small increase in price. The gear set are normal helical cut gears. For water jet installation we purchase the ratio to obtain max output and the right RPM as per a propeller is matched to RPM. The water jet manufacture also make small changes to the pitch to achieve the best efficency.
For water jets we purchase these boxes without a reverse gear set and wet clutch pack.
For interest the power loss in these boxe is around 2.5 %
Regards Don

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