Honda Outboards BF40A/BF50A Service Manual, Page 232Get this manual
HONDA BF3SA4E5A
At collision
Because the piston lowers and pressures the oil in the oil chamber when the outboard motor is struck with an obstacle while cruising, the shock valve opens and oil enters between the piston and free piston to absorb the collision impactWhen the outboard motor is away from the obstacle, the piston rises by the dead weight of the outboard motor and the thrustThe oil between the piston and the free piston flows through the return valve in the piston to the oil chamber I