Now ... wait a minute ...
I must have misunderstood the situation.
I assume(you know what they say about that), that anyone on a truly BIG boat ... this wouldn't be an issue, and most certainly, for some people, a dishwasher would be nice(not for me). The idea of using less water is nice too.
So again, given my assumption, I garnered that many boater's with boats not really all that big(like 30' to maybe 35' or so), who don't have the on-board facilities that the more huge, more large, more gigantic, interiors and extra space doing almost nothing, who would like a dishwasher, don't have the space and infrastructure(within the boat) to have a "normal" dishwasher.
My "imagination", came up with something akin to those hand-cranked washing
machines, which take up little space and no infrastructure(such as always available power, water and such.
Personally, I only cook what I will eat and cook more "liquidy", soups(like chicken/turkey soups. I also "re-use"(gastly), the pan from a same day meal of soup or raviola as the pan for the next meal ... WITHOUT washing, as long as the tastes of the first meal won't interrupt the taste of the second meal.
Often, I make aluminum
foil shapes on the outside of my cook pan, the force-feed it into the pan for those meals(like beans and such), that just don't mix good with the next meal.
For utensils, I use good plastic ones and clean them while I eat, the simply wipe them off(paper towel), and I'm ready for the next meal.
If the dishwasher is important, put one in ... if you don't have space, use you imagination to figure something less viable, but still worthwhile.
There's not way I'd ever use what I described, because I have other ways to get around the need, using NO WATER.