Original equipment on 1978 Gulf Star

[henryj2]

We purchased our 44' Gulf Star trawler three years ago. Heads both fore were fresh water Jabscos. Some literature I obtained from a Gulf Star club in St. Pete, Fl suggests that originally the boat came with Raritan head and I am suspecting they were sea water but am not certain. Point is, in the engine room, on the starboard side of the starboard engine there is a thruhull with a brass fitting of about 6 inches with two capped outlets. I'm guessing this might have served as the water intake for the heads before alteration. I would like to use this fitting as the raw water input for a watermaker I want to install but would like more information before proceeding.
Anyone have any knowledge about this situation?
Thanks in advance for any help.
Jim H.