OMC Evinrude Johnson Screw 3/18 -18

An OMC Evinrude Johnson screw with the designation 3/8-18 is a standard size screw with 3/8 inch diameter and 18 threads per inch. It's likely a general-purpose screw used for various mounting or assembly applications on Evinrude and Johnson outboard motors. 

Here's a more detailed breakdown:

3/8-inch diameter:

This refers to the screw's diameter in inches, typically measured across the head.

18 Threads per Inch:

Tis specifies the pitch of the screw's threads, with 18 threads per inch being a common size for general-purpose applications

OMC, Evinrude, and Johnson:

These are brands of outboard motors that likely used this screw size

Applications:

The Screw is probably used for attaching various components, such as fuel lines, drain plugs, or other parts within the outboard motor.