Relative to cruising, Macs come almost completely stripped, except for cushions on the berths (beds) and one or two sinks, each with a hand-pump faucet and a 5 gallon collapsible water jug.
As a couple of empty nesters, we could get by with 10 gallons of water for 4 nights out, using the Mac's hand pump faucets. That's wasn't for drinking, except for coffee. With pressure water on the C-18, we use double that, but could probably use a little less if more careful.
Most previously-owned Macs have an optional dealer-installed portable toilet, and it's usually a 2.8 gallon model, either Thetford Porta-Potty or Sealand Sanipottie. That's good for us for 2 nights if I do #1 in it, but if I use a jug for #1, we can double that (I drink a lot). You can also get 5.2 gallon or larger models (won't fit in the 2005-later 26M), but the bottom can get heavy to carry and awkward to dump. As an alternative, you might consider a spare 2.8 gallon bottom. If you'll be going to Ontario across Lake Erie, you'll need a potty plumbed with a vent and pump-out fitting on the deck. Unplumbed portable toilets are illegal there. [edit to add] That includes Pelee Island.
Many, if not most, Macs have an optional dealer-installed Origo single-burner alcohol stove. We liked ours and denatured alcohol is easy to find. Some even have a two-burner. The canister holds a quart and that lasted us for longer than a weeks worth of days. We now use a portable butane stove on the C-18 and one fuel can lasts about as long. Not as easy to find as alcohol though.
Some extended cruisers don't use ice or refrigeration. There's lots of food that doesn't require it. Still, we like our cold drinks. We had two coolers in the 26X, one under the aft dinette seat for food, and a
50-quart Igloo Ice Cube on top of the aft galley seat for drinks (Duane's idea).
Duane is right about the cheap 48-quart Coleman cooler, a Mac option for under the aft dinette seat in the 26X. The 50-quart Cube is also a 3-day cooler and not much better. Neither hold cube ice more than a couple of days. Not an issue if you frequently stop in marinas. We used frozen half-gallon milk jugs of water (Don T's advice) and they held out for four overnights. Block ice just lasts longer than cubed.
[edit to add] Duane's idea of using a hand bilge pump to empty water from the coolers into the galley sink worked great.
Electricity use is hugely variable. With a single Group 24 deep-cycle used for both house use and outboard starting (on a Mac, not on our C-18's 4HP kicker), you have about 35-40 amp-hours (half the battery capacity) to play with. Discharge below 50% and you won't get much life from the battery(s). If you use the battery(s) for both house and starting, carrying a jump start pack.
The Mac cabin lights each draw 1.5 amps, so if you use 2 for 3 hours each evening, that's 1.5 x 2 x 3 = 9 amp-hours per evening. We used them as little as possible and now have LED cabin lights in the C-18. Not nearly as effective as incandescent, but adequate in the smaller C-18, especially the red ones.
The Mac navigation lights are about 0.75 amps each, so if you sail for two hours after dark, that's 3 amp-hours. If you motor, you need to add the steaming light to that usage, but of course the outboard alternator, not the batteries, is powering it and the nav lights.
The Mac doesn't come with an anchor light, but if you add a 10 watt one, that's about 0.75A x 10 hours or 7.5 amp-hours per evening. An LED one uses about 1/4 that much. Just make sure it's certified to comply with USCG 2 nautical mile visibility standards.
A stereo can use 1-2 amps, so 6 hours of music can use 6-12 amp-hours per day. A fixed VHF radio typically uses 0.5 amps on standby, 1.0 amps on receive, and 5 amps when transmitting. A handheld uses much less. IIRC, our fixed GPS/Sounder used 0.25 amps. Not sure about handheld. [edit to add] A cooler-sized 3.5 cubic foot dual-voltage Engel refrigerator can use 17-20 amp-hours every 24 hours.
Macs do not come with a shorepower battery charger. Previous owners may have added one, or you can. You can also recharge the battery(s) by motoring (with a large enough motor), but not as quickly as with a good 3-stage shorepower charger.
Hope this helps,
--
Moe
Note: there were some electricity/battery-related posts below this post, that the mods split off into a new thread
Batteries & Extended Cruising. Just for future reference. -- Moe