Hi Witz,So in what orientation should you store a 4 stroke outboard?
Each motor is different and every manufacturer states how their motor should be stored in their Owner's Manual. Usually the motor has "feet" to indicate which side the motor can be laid down upon.
Yamaha's new 4hp and 6hp can be set down in three horizontal positions (on the face and port and starboard sides) without oil leakage. A true plus over other motors which can only be laid down on one side or stored vertically to prevent oil leakage.
The short answer is read your Owner's Manual and see how the Manufacturer designed the motor to be stored (on what side).
Hope that helps.
Cheers-
Stephan