2009 Yamaha F40 Outboard Service Manual, Page 247Get this manual
Lower unit
Removing the lower unit
Make sure to disconnect the battery cables from the battery, and then remove the clip from the engine shut-off switch When removing the lower unit with the power unit installed, make sure to suspend the outboard motorIf the outboard motor is not suspended, it can fall suddenly and result in severe injuries Do not hold the propeller with your hands when loosening or tightening it1Drain the gear oil2Remove the cotter pin3Set the gear shift to the position, and place block of wood between the anticavitation plate and the propeller to keep the propeller from turning, and then remove the propeller nut and the propeller