IC30 and hot water heater
Congrats on your new boat. I have an 88 TRBS with wing keel -- and would suggest the following: Stongly suggest you review the IC30 web site (see link below) and acquire the 'tech talk manual' (under publications) AND join the IC30 to get the quarterly 'MainSheet' Magazine with its tech articles. It will be the best $ you ever spent. It will answer your and many other questions. Regarding a hot water heater -- my boat has the 6 gallon Seaward square unit installed just forward of fuel tank which is below the aft quarter-berth and wired through a switch on electrical panel's AC side. Unit is is both electric and engine hot-water heated (I have a universal diesel fresh water cooled -- with bypass running through the hot-water heater). you should be able to install it only for electric (and do engine later if fresh water cooled). get the stainless steel version -- eliminates corrosion and magnetic problems with autopilot compasses when installed below decks (e.g. raytheon 4000+). mine works great. Regarding exhaust hose -- no experience (thankfully), but hear it's a big pain. Regarding cooking -- I don't do much, but many who do use propane grills mounted on stern pulpit using little propane bottles (be sure to store these properly -- i.e. NOT below decks or lockers not vented to the outside). would recommend keeping propane oven/stove, I have used both oven and stove once and awhile and both work great and were needed (bad outside weather and/or cool out). Regarding ice-box -- Catalina has improved it over the years, have read about adding insulation underneath (be careful to NOT fill-in the area the wet-exhaust hose runs in). Also, the lid now has added insulation (2-4" encased in plastic). Suggest putting a stopper in the bottom drain, the cold water keeps the cooler colder longer. Mine eats up about 3-4 bags of ice every 2 days or so -- if running the over/stove it goes quicker -- but still better than any of 3 36qt coolers kept on the main saloon sole during week long trips). Remember if you consider a refrig, you must consider increasing battery power and a good 3-4 stage 20amp+ battery charger, so the costs can continue to escalate, all why I haven't! Best of luck...
