[GeorgeB]

I did the San Francisco to Oahu trip this summer and here are a couple of observations. We budgeted one gallon of water per day per person. In your case, I calculate 72 gallons, assuming an 18 day passage (What kind of boat are you sailing and will you be in race mode?) In reality, we used much more water as you use more water than you think in cooking and making coffee. And when we were in the tropics, we were also drinking copious amounts of it too. We washed dishes (and ourselves) in salt water, but did fresh water rinses (sparingly). You should plan on using more than the gallon per person per day factor. We also had a Sprectra Ventura 200T watermaker on board. Depending on how you install it, you may not be able to make water close reaching or surfing at speeds (eg. the siphon action along the hull or the system ingesting air/foam and creating a “vapor lock”). We were fortunate insomuch that our thru hull was on the port side (Stb tack most of the way). We could make the 6 gallons per hour rate as long as our boat speed was below ten (we did not have a scoop on the water intake). The watermaker consumed approximately 9 amps/hour and the start-up and shutdown (flush) operations took about 40 minutes to an hour. Needless to say, this was a big energy hog. The other problem is you have to run it every five days unless you pickle it. Pickling is another involved process that eats up a lot of amps too. We ran ours three times during our 12 day passage.