SAN 230 ZR409 Plug (Does anyone know whats this goes to ? )

[Dave Rittiman]

Question i have a 2009 SAN 230 with a ZR409 and was just putting oil in and noticed a plug and was wondering what it might go to ? Should it be covered or is something sposto be plugged into it ?

First picture shows the plug.

Second picture shows the location looking with engine hatch looking towards the back of the boat.