How do you remove the lower unit on a 4 stroke 90 hp mercury?

To remove the lower unit on a 4-stroke 90 hp Mercury outboard, start by ensuring the engine is in the neutral position and disconnect the battery. Remove the bolts securing the lower unit, typically located on the rear and sides, and then detach the shift linkage and any associated wiring. Carefully lower the unit, taking care to prevent damage to the drive shaft and water pump. Finally, inspect the gaskets and seals for wear before reassembling.