Water weighs about 8-1/3 pounds per gallon. Gas weighs about 6 pounds per gallon. Every pound you add changes your boats sailing characteristics, weighs it down, and slows it down. And the Cal-34, at 9,500 lbs. displacement
, is designed as a pretty light-weight 34 footer, so extra weight is going to affect it more than it would a boat designed with a relatively high D/L ratio.
As such, I personally would not add more than about 5% to the boat's displacement. That would be 475 lbs, and still allows you to add something like 20 gallons of gas and 40 gallons of water.
Now you have to consider where you are adding this weight. Obviously you're creating a problem if it is all on one side, so you have to balance it port and starboard to avoid listing. You need to get it down as low as possible, though the Cal-34 has a ballast ratio of almost 40%, so it won't be the end of the world if the weight is not right down in the bilge
The general rule
of thumb for water is 1 gallon per person, per day. Are you really thinking of spending two months away from facilities where you can refill? Then you need 120 gallons, which is really too much for this boat. If you are going to be doing a more typical cruise
, where you are usually able to refill every 2-3 weeks or so, then 60 gallons becomes plenty. If you are cruising through the Caribbean
, where you can fill up every few days then the 25 gallons you have is enough. In fact, that's exactly what a boat like the Cal-34 was designed for.
As for gas, only you can decide how much and how often you will run the engine
. Some cruisers do it all the time. Some hardly ever. I'm one of those "the boat was made for sailing" types. Some people, you wonder why they didn't just buy a powerboat to begin with. I used to dock
next to a guy who--quite literally--ran his engine all the time, even when he had the sails
up (which, frankly, I think he spent more time motoring with his sails
down than he did with his sails up). I'm quite sure that he burned as much diesel
in the course of one day of day-sailing as I would burn during a 2-week cruise