Boating newbie - advice required please.

Bigger the motors and bigger the boat or faster the boat; bigger the fuel burn. Most weekenders are designed to run on about 7 to 10 hours on a tank of fuel at cruise speed, but that's a very rough and variable average. Single or twin engine is going to affect speed and fuel burn greatly, and also maneuverability around the docks.
To really give you a satisfactory answer to most of your questions here I'd really have to write a book. Suffice to say though that you're a long way from traveling across the Pacific and you wouldn't want a boat capable of doing that for what you want to do now. Exploring is one of the most enjoyable parts of boating, both the travel parts and the learning (preparation) parts. So instead I'm going to refer you to what's already been written here on YF. All of those questions have been discussed in great lengths here. Today you have threads running that discuss what makes a live-aboard for different people (when a boat become a yacht) and passage-makers (expedition yachts). Beyond that go to the SEARCH button. Key in terms like "Twin engine", "Live-aboard", "Fuel-Burn", "Express Cruiser", "Motor Yacht", and any other term you can think of or term you see in one of the posts that you don't fully understand or would like to know more about. It's all here. In 56 years on the water I've never run into a more informative source than YF. You can see how many posts I've made over the years. If I averaged even 5 posts per thread I've been involved with that's a lot of topics, and I doubt I've been involved with 3% of what's been discussed. Or you could just SEARCH for post by certain participants and that will lead you to a wealth of topics. I'd suggest myself, K1W1, Pascale, Marmot and Capt.J for starters. Just those 5 names will lead to about a year's worth of reading, and a fair amount of knowledge and entertainment I think. Enjoy.

Absolutely Judy. That topic alone could generate a book, which is why I kept my comments as general as possible for this stage of the OP's learning process and instead sent him into the SEARCH feature where he'll find much more in-depth conversations on the topics he needs to learn about.

If you want a blue water boat with a range of 3000+ miles, it has to be a displacement hull, a trawler. There are some very nice ones out there for entertaining guests. I would say go with a boat in the shorter length as it will be cheaper to buy, buy fuel for, maintain, learn to cruise, find a berth and to learn on. Ocean going boats are more about construction, design, and maintenance by the previous owner, than about size. The semi-displacement or a hull that planes has to be built light to get up out of the water. This means little fuel and fresh water capacity because of the weight. These boats demand a lot of horsepower and the problem with that is designers will take a diesel engine and get that horsepower by injecting more diesel into the cylinders resulting in engines with are worn out in a few thousand hours or less. If the same engine is operated at a lower RPM, the time between overhaul is 10,000 hours and more. A semi-displacement or one that planes that is operated at displacement speeds will have the problem of slobbering also known as wet stack. This can destroy an engine. A diesel needs to be operated at more than 40% of the power that it is designed for when used for a rating of continuous heavy duty service, that 10,000 hour plus usage. Google cat diesel engine rating definitions. take the first thing that comes up and go to page 8. An engine can be operated at less than 40% power if it is used for say 8 hours and then brought up to 75% to 100% of continuous heavy duty service for an hour. Several books that may interest you are Dave Gerr’s The Nature of Boats and Voyaging Under Power by Robert Beebe.

MY Obsession has a displacement hull and is a trawler?

YACHT OBSESSION:: 180' Oceanfast Motor Yacht

Judging by what you're looking for. What about a 44' Lagoon powercat. A ton of entertaining room and very economical if run at 10 knots.....but will cruise at 17 knots if need be.....very stable, easy to run, etc etc.......Flybridge......

I just bought that barge. Don't talk about it anymore, or I'll have to charge you a licensing fee.

A power catamaran does give more space. Finding a wide berth might be a problem and it is important to keep the weight low for any speed advantage above a displacement hull. Some trawlers are Dashew, Seahorse Marine, Romsdal North Sea Trawlers, Malahide North Sea Trawlers, Willard Marine, Skookum Marine, Cheoy Lee Trawlers, Stephen Seaton’s Boats, Beebe’s Passagemakers, Knight & Carver, Kadey-Krogen, Nordhavn, Cape Horn Trawlers.

I do not know much about Power Catamarans. Maybe someone can give a list.

It has a full beam master in the stern with a king size bed. It also has 3 heads and 2 other staterooms that have a full (tapered) size mattress in each. But has a huge flybridge, very nice aft deck with table for it's size, pretty nice salon, and a nice seating area on the foredeck. Stable, easy to maneuver with the engines so far apart, fuel efficient, and in the owners price range on a relatively new boat.....2006+

Lucky, you.

The price was just reduced by €2 million.

Timing is everything.

P.S.- Was that the crew cheering, "This brew is on you!"?

P.P.S.- Back to the OP, perhaps these links will provide some interesting viewing.

Design of elegant yachts, aluminium boats, fuel-efficient boats, sail boats, cruising boats. - Dennis Harjamaa Yacht Design, Elegant Yachts, Aluminium, Fuel-Efficient, Sailing, Cruising Boats.

The Fleet

Hatteras LRC boats for sale - www.**************