Marine propulsion unit attachable to boats

934,877. Outboard motors. INSTRUMENT RESEARCH LABORATORIES Ltd. Nov. 29, 1961 [Sept. 20, 1960], No. 32255/60. Class 114. An outboard motor or drive, which can tilt about a horizontal transverse axis centred at 8, is provided with a feeler 34 pivoted to the base of the underwater housing at 35 so as to act to release a spring-loaded latch 37 on striking an underwater obstacle and allow the motor or drive to tilt out of the path of the obstacle. The feeler 34 is connected to the latch 37 by a stainless steel cable 36 passing through an eye 38, the latch acting on a fixed pin 40, carried by the transom bracket 4, to prevent the motor or drive from tilting. As described an inboard I.C. engine drives the propeller 13 through a chain-drive and clutch, disposed in the casing 17, and shaft 16. A manually operated catch may be provided comprising a lever pivoted to the latch housing 38 which may cause the latch to move against the spring and release it from the pin 40. The Specification also describes a rudder 12, having an adjustable fin 12a, mounted on the motor or drive casing and rotated by the shaft 15 which rotation is transmitted from the rudder post 9 through a mechanism which is described and claimed in Specification 934,878.