84 23' Center console tank size

[Sullivan21]

Seacraft 84-we are in the midst of replacing ours with a tank from Sunshine tanks in FL. We have a 23 that is one year newer than yours. The box it sits in beneath the floor is 29" wide by 14" deep-the enclosure is open to the bow, enclosed on 3 sides. I added drains with little pvc fittings so that water will flow into the bilge. Our tank will be a little over 100 gallons. Good luck with your project. We had to cut ours out in pieces with a metal/aluminum cutting tool called a nibbler. No more foam-we are using 5200 and strips of starboard.