this invention relates to a marine jet drive having improved operation , especially in regard to having efficient adaptation to propulsion engine and hull design ; having a drive shaft with flexible coupling at each end , internal to the jet drive ; having through - the - nozzle engine exhaust ; having simplified , combined means of steering and reversing ; having controllable nozzle aperture and trim control ; having combination reverse flow deflector and trim plane ; having means to disengage the engine from the jet to obtain true neutral ; having protection from and removal of debris in the water intake duct ; generally having fewer overhauls , easier serviceability and lighter weight .