hi there, I am pretty new to this forum but can tell you that this post will not get any answers, look at the information you provided its basically nothing. Tell everyone what boat it is in what area of the boat some pictures etc. I almost feel like I am replying to a robot....who on these boards would not provide more information?
Unfortunately many members do the same thing, ask a question with little details… first thing you need to do is find the brand and model of the water heater and see if it’s still available. If it is, getting the same one will make the job easier. If not all you have to do is find one that fits and of the same voltage, 120 or 240v.