Here's what we bought
Chuck: Last summer or the summer before, we bought a "Sealand Sanipottie 962, Parchment" to replace our Thethford portapottie that originally came with our boat. Sealand makes another one that is virtually the same, but has a bigger holding tank. But that bigger, ticker, tank makes it too thick to fit under the boards to the "V" berth, according to our measurements. Our boat is also a 1980, and we have had it since it was new. We actually bought a second one of these portapotties because we wanted a second holding tank for when we cruise our boat. I had actually purchased a tank directly from Sealand's part's division, but there was a mix-up. I had to buy all of the parts to the tank separately, like the cap, and the slider valve, and tank, which would have been easy enough to assemble. But, the total price for all of these pieces was much more than for an entire 962 toilet from West Marine. (The total price for all of the pieces is where the mix-up occurred). I ended up returning all of the pieces and purchasing a 2nd 962 Sanipottie with a West Marine discount card that I had.It would be nice if Sealand would mold a holding tank sized between the two that they currently make, but I think it is unlikely that they ever will build that mold. The smaller tank is easy to carry. It is a little messy to empty. I think that other manufacturers have a spout to help empty theirs without splashing.I'm not necessarily recommending this portapottie. It works pretty much OK, I actually liked my original Thethford better in some ways. It was easier to clean, but the 962 does fit. (My original Thethford portapottie didn't have a holding tank that could be seperated). One thing that you have to remember about the Sanipottie 962 is to pull-out the slider valve SLOWLY, otherwise, pressure from the tank will be expelled from underneath something that you just expelled. I guess that shows how well the valve seals. I hope that this helps, Aldo