Thanks for noticing this. I looked in the editor, and the mass of the ship is 1923 tons. 1800 tons of this is the hull (the guns are 90). It looks like this 1800 figure is one I wrote in by hand, rather than calculated, and I don't remember where I got it from.
I can see the relation displacement = about 1.5*burthen in a few places. I have one source, "The Command of the Ocean" by N A M Rodger, on the 18th century royal navy, that says "for a fully stored warship" the displacement is about twice the burthen. Do you know what the state of storage is for your figures?
This is something I am reluctant to mess with, as I am happy with the way the acceleration, stability etc. are tuned at the moment. But I will have to look at this stuff again if I ever get around to flooding and sinking.