Let’s start with the more-easily-calculable things, and get into the harder ones later.

Fuel

The most direct path of the great loop is, plus or minus, 6000 miles, but you’re going to stop in at marinas not right on the route, explore some rivers, bays, inlets, etc. So a more realistic round number is 6000 nm (nautical miles: 1nm = 1.15mile.)

The next part is pretty boat-dependent, since we’re calculating mileage efficiency. Every boat is different, and every captain will use their resources differently, but let’s try to give some rough criteria to work with. Boattest has been doing reviews of boats for decades and has fuel efficiency reports for many of them, so you may be able to get numbers for your boat right off there, or be able to find them on forums or other review sites. They’re really important numbers to know, since you’ll want to know what your range is for some of the longer legs of the loop. If you can’t find numbers for your boat, you’ll have to understand some basics and get some rough ideas.

Every boat has “efficiency humps” in their nm/gal vs. speed curve they need to be aware of and work around. Your first hump will be before “displacement speed” (also called “hull speed”). In a 40 ft boat, it’s a hair over 8 kts, in a 30 ft boat, it’s a hair over 7 kts. Stay under displacement speed for your best mileage. You’ll spend a significant portion of your loop doing displacement speed, because lots of the ICW and other inland waterways have speed limits, so this will be the overwhelming factor for your mileage. Here’s some really rough ideas for different types of boats, staying under hull speed:

• 30 ft gas sailboat: 4 nm/gal
• 30 ft gas cruiser: 1.75 nm/gal
• 40 ft diesel sailboat: 3 nm/gal
• 40 ft diesel trawler or catamaran: 2 nm/gal
• 40 ft diesel cruiser: 1.5 nm/gal
• 40 ft gas cruiser: 1.2 nm/gal
• 50 ft diesel cruiser: 1.0 nm/gal

In general, at hull speed, you should meet or exceed 1.0 nm/gal. Just be careful, and try to get numbers for your boat. You’d be shocked at how adding less than 1 kt of speed may nearly halve your fuel efficiency when you approach and pass through hull speed.

Cruisers/planing hull boats can go much faster than hull speed, when the boat steps up onto a “plane”, and rides somewhat on top of the water, doing 14+ kts. However, this comes with a huge decrease in efficiency:

• 30 ft gas cruiser: 1.2 nm/gal
• 40 ft diesel cruiser: 0.6 nm/gal
• 50 ft diesel cruiser: 0.4 nm/gal

Depending on your schedule on doing the loop, if your boat is capable of it, you may plane virtually none (outrunning a storm only), some (NJ coast, FL gulf crossing, etc.), or often. You’ll have to think about how much you like the journey vs. enjoying your destination to figure out how much your time is worth.

So, back to where we started, how much do you think you’ll travel at planing speed vs. displacement speed, and what nm/gal do you expect?

• 30 ft gas cruiser with a mix of fast/slow: 1.5 nm/gal -> 4000 gallons
• 40 ft diesel trawler that never planes: 2 nm/gal -> 3000 gallons
• 40 ft diesel cruiser with a mix of fast/slow: 1 nm/gal -> 6000 gallons
• 50 ft diesel cruiser mostly planing: 0.67 nm/gal -> 9000 gallons

If you pay a lot of attention to your fuel refills, you can use the Waterway Guide Fuel Report to help find the cheapest fuel coming up, and optimize your stops around it. At the time of writing, that means rarely paying much over 2$/gallon for diesel, or 2.50$/gallon for gas. But if you don’t pay attention, you can easily find yourself out of fuel and the only marina near you is selling what you need for 4-5$/gallon.

If you really have no idea yet, assume 1 nm/gal, paying 2.50$/gallon, and that’s 15,000$ for your fuel budget for the year. Maybe you’ll surprise yourself and save a bunch of money for the wine budget.

One last consideration is generator costs. If you don’t spend every night in a marina, you’ll be running your generator. If you save money on marinas by being on anchor, this could add up to a nontrivial sum of money, especially if you run your generator for hours on end or all night to keep the A/C going. Generators on loop boats often use between 0.5 and 1 gallon per hour, so if you run the A/C all night on a hot evening, you might end up burning through 10 gallons of fuel, which adds up real fast. Just something to keep in mind.

Moorage

People usually ask about the fuel prices first, but it’s the easiest to calculate, and also will likely end up being a lesser expense to moorage, so make sure to think deeply about moorage costs as well.

This expense hugely depends on what kind of boating you like to do. If you’re loners that enjoy a pretty sunset in a cove with no one else around, and you spend most of your time at anchor, then this expense will be very low. If you love wandering the docks with a drink in your hand looking for folks to chat with every night, then this expense will likely be very high. But no one can tell you how much this will cost, since it’s a very personal decision for how you want to spend your year aboard.

In general, in most populated areas of the loop, staying in a marina is going to cost you around 2$/ft/night, with 10-15$/night for power. If you stay in a super swanky marina, it may be 3$ or more per night — we’ve seen as high as 12$/ft/night in New York. In the middle of nowhere and/or swing seasons, we’ve paid under 1$/ft/night and 5$/night for power. Look around at all of the marina options in an area — it’s amazing how much variation in cost there may be for what feels like essentially identical services.

Some marinas will have the option of renting mooring buoys, which are a middle ground for many folks. Much less risk of any dragging in the event of winds/questionable bottom, easy tie up, no anchor cleanup, and no worrying about swinging into neighbors. Mooring buoys often only cost 20$ or so, with up to 40$ in really nice areas (where the marinas are usually 3$/ft, so still a substantial discount.)

Random rough numbers to give you an idea of a year on the loop (assuming 1.5$/ft/night + 10$/night power on average):

• 30 ft boat, 1/2 marina 1/2 anchor: $10000
• 40 ft boat, 3/4 marina 1/4 anchor: $19000
• 50 ft boat, 100% marina: $31000

Maintenance

This is where numbers start getting a lot fuzzier, and depends a lot on factors like your comfort repairing your own boat and condition of your vessel.

If you have a boat over around 10 years old, then you’re well into the curve of when you’re on a constant stream of things breaking. Most things on a boat that’s used fairly regularly have a short life span. Take your house, make all the parts low-volume semi-custom parts, then shake it around 24/7 for a year, and see how many things break. That’s boat life.

There’s obvious maintenance like changing the oil and fuel filters every 100-200 hours (which will be 5-10 times on your loop), which are nontrivial costs just for materials, much less man-hours of labor. But you will have other stuff break, at unfortunate times. Your raw water pump will probably have an issue, because they do that every 1000 hours or so on many boats. Your fresh water pump will probably have an issue, because they do that. Your toilet system will probably have an issue, because on most boats they’re often not really designed for full time liveaboard usage. How new is your bottom paint? That needs redoing every few years, especially with the miles you’re going to put on it. Touch a submerged log and bend a propeller and you’re coming out of the water for a few days and out several thousand dollars. The list goes on and on.

Marine technicians are, like any repair profession, often ~80$/hr or more, and if they need to come to you because you’re dead in the water stuck on anchor somewhere, there’s often heavy travel and emergency fees on top of that. Haul out fees are often 500$ or more, and then you need to find a hotel on top of that. Repairs are expensive and time consuming and never on your schedule.

For a really super rough number, and a boat starting the loop in reasonably good shape, make sure that you have 1000$/month tucked under a mattress for unplanned maintenance, plus a few thousand dollars over the course of your loop for planned maintenance (oil changes, paint, zincs, etc.) Let’s say $15000 for the year. You might get away super lucky with a fraction of that, or you might get screwed by a major breakage that costs a multiple of that. You’ll probably end up not too far off that number, though.

Food/Clothes/Toys/Misc.

The last category is actually the easiest. First time liveaboards tend to be very worried about additional costs over how they were living their life on land. Realistically, you spend about the same amount on these daily things as you did at home. If you like eating out, you’ll eat out a lot, and spend money there. If you go to a grocery store, it’s going to cost about the same as it did near your house. You’re probably going to go through, if anything, less clothes than on land, though maybe more opportunities for shopping might be a weak point for you to think about. But in general, take whatever you budget for these sorts of incidentals around home and match it for the loop. You won’t be far off what it turns out to be.