Dual speed transmission

A two speed transmission system mounted for driving a marine craft:

• an input shaft coupled in direct connection with a driveshaft of an engine of the marine craft;
• an output shaft coaxial with the input shaft coupled in direct connection with a driveline of the marine craft;
• a first gear train for transmitting drive from the input shaft to the output shaft at a low speed fixed first gear ratio;
• a second gear train for transmitting drive from the input shaft to the output shaft at a cruising speed fixed second gear ratio;
• a first friction clutch operable to engage/disengage the first gear train, whereby the first friction clutch is engaged to drive the marine craft in the low speed first gear ratio;
• and
• a second friction clutch operable to engage/disengage the second gear train, whereby the second friction clutch is engaged to drive the marine craft in the second gear ratio;
• wherein the input shaft is isolated from driving interconnection with the output shaft by disengagement of both clutches;
• wherein in shifting between the first gear ratio and the second gear ratio one of the friction clutches is disengaged using controlled slippage while the other friction clutch is engaged using controlled slippage;
• and
• wherein the second friction clutch is operable to engage the output shaft in direct 1:1 drive with the input shaft, and the first friction clutch is operable to connect the input shaft to the output shaft via a lay shaft such that the first gear ratio other than 1:1.