Propulsion installations for boats, more particularly for high-speed launches

Claim 1

A propulsion installation, comprising: a power unit; a reduction gear mechanism, a primary input shaft of the reduction gear mechanism drivingly connected with said power unit; an output shaft of the reduction gear mechanism arranged to drive propulsion means; wherein the improvement comprises the provision of: an auxiliary engine; a secondary input shaft of the reduction gear mechanism arranged to be driven by the auxiliary engine; means to decouple the said output shaft from the primary input shaft; said reduction gear mechanism including means to drivingly connect the secondary power input shaft to the output shaft with such output shaft decoupled from the primary input shaft; and means including a freewheel device to drivingly connect the secondary power input shaft to the primary input shaft for starting of the power unit, said freewheel device permitting transmission of torque from the secondary power input shaft to the primary power input shaft to rotate a shaft of the power unit in the direction in which such shaft is rotated for starting of the power unit in which the power unit comprises only two engine units, and in which the said means within the reduction gear mechanism for drivingly connecting the said secondary power input shaft successively with each primary input shaft comprises a transmission mechanism comprising a rocking support; a pair of driving gearwheels mounted on the rocking support, means to rock the support between three positions; and a pair of starter gear wheels arranged to be driven to drive their respective primary input shafts during starting of respective engines units; the rocking support when in a first said position thereof having a first of said pair of driving gearwheels in driving engagement with a first of said starter gearwheels, when in a third said position thereof having a second of said pair of driving gearwheels in driving engagement with a second of said starter gearwheels, and when in a second and intermediate position thereof having both of said pair of driving gearwheels out of engagement with said starter gearwheels.