The serial number tag is located on the SWIVEL BRACKET (port or starboard); or, check the INSTRUCTION PLATE, located between the thumb screws above the steering tube.
To view an image of the plate location, CLICK HERE

Mariner Outboards

The serial number tag is located on the top outside edge of the CLAMP BRACKET; or, on top of the SWIVEL BRACKET (port or starboard).
To view an image of the plate location, CLICK HERE

MerCruiser

Engines: The serial number tag is located near the STARTER, by the flywheel housing; or, on the ROCKER ARM or FLAME ARRESTOR COVER.

Transom plates: The serial number tag is located on the INNER TRANSOM PLATE inside the boat; or, on the UPPER SWIVEL PIN.

Sterndrives: The serial number tag is located on the UPPER DRIVE SHAFT HOUSING (starboard side or on the back of the housing).