1984-1986 Mercury Force 4HP Outboards Service Manual, Page 61Get this manual
GEAR TRAIN DeacrlptlonThe gear train redirects vertical engine rotation to the propeller which is on horizontal planeThe engine driveshaft continuously revolves clockwise when the engine is running but propeller rotation (forward or neutral) is controlled by the shifting mechanism of the gear IralnOper.tlonThe drive shaft is splined to the pinion gear which meshes with the forwar gearThe propeller shaft engages with this gear by means 01 shift clutch
(CLOCKWISE)
The shift clutch moves back and forth by followin the cl utch shift cam on the end 01 the shift rodwhich moves up and down
When the motor is shifted into forward gear the shift clutch engages the gear and turns the propeller clockwiseFigure 10