I'm not trying to be a wise guy here...The drain plug is located in the lowest part of the V in the transom. Most of the larger boats like yours have the screw in brass plug that screws in from the outside and is tightened with a 9/16 wrench. Same thing if it is the standard 7/8 rubber/brass plug that also screws in from the outside.
do yourself a favor and go buy like four extra plugs... place them in several spots in your boat where you know you will see them when you launch the boat. This serves as a good memory booster to remember to put in the plug... and give you some spares in case you forget to put it it in....