Mount Desert Island Marathon Fueling Plan & Pace Chart

MDI Fueling Strategy

MDI has roughly twice the climbing of Boston, about 1,650 feet, and it puts the two biggest climbs at opposite ends of the race. The first 3.4 miles gain about 220 feet to the highest point on the course. The last climb, from Somesville at mile 20.5 to the top near mile 24.9, gains about 195 feet in two steps when you have the least left. In between is a sawtooth that never lets effort settle. The 2025 median finish was 4:23:51, and 91 percent of finishers ran a positive split, with the median second half 12 minutes slower than the first. Most of those minutes are lost at the back end, and most of them trace back to fueling in the first 16 miles.

Start with what the course hands you, because it is less than you think and it arrives late. Fluid stations sit roughly every two miles with water and lemon-lime Gatorade. A four- to six-ounce cup is worth about 7 to 11 grams of carbohydrate and 55 to 80 milligrams of sodium. There are no gels at all until the mile 16 station, which is where GU starts, in various flavors (the race FAQ lists salted caramel, which has 20 mg of caffeine). A mid-pack runner reaches mile 16 around two hours and 35 minutes into the race. If you take every cup before then you have collected roughly 60 grams of carbohydrate in two and a half hours. At 75 to 90 grams an hour, carry at least six gels and treat the Gatorade as hydration.

Take your first gel around mile 2 in the dip near the Sieur de Monts entrance, between the two opening climbs. Do not eat on the climb from 2.5 to 3.4, and do not eat on the drop that follows. Mile 4 falls about 150 feet in half a mile, it is the steepest descent of the first half, and it will pull you 20 seconds a mile under goal pace if you let it. Run it controlled and take the second gel around 4.5 on the flatter ground before the Otter Creek bump at mile 5. That rise is about 70 feet and the official course description calls the whole stretch a downhill sweep, so do not be surprised by it.

Cooksey Drive, miles 6.3 to 8.3, is closed to traffic and you can run the tangents on either side of the road. It climbs about 60 feet early, then descends to Seal Harbor beach at mile 8.5, the flattest ground and lowest point of the first half. That is your third gel, with restrooms at the Seal Harbor wharf (mile 8.1) and beach (mile 8.5) if you need them. The next four miles are the hardest to fuel on, because Route 3 between Seal Harbor and Asticou goes up and down 50 to 70 feet four or five times. Eat on a crest, not a climb. The high ground near the Route 198 turn at mile 11.4 works, and the mile 11.5 spectator zone is a good landmark. By the half-marathon start line at 13.1 you should have four or five gels in you. If you have three, you are already behind.

Sargeant Drive, miles 14.1 to 17.3, is the engine room. It is closed to traffic, it hugs Somes Sound between about 20 and 70 feet of elevation, and it is the gentlest stretch of the day. Take a gel from your own supply around 14.5 and the first course GU at mile 16, or your own if you have not trained on GU. Then eat nothing on the climb. The turn onto Route 198 at 17.3 goes up about 60 feet by mile 18, the Butler Road loop dips, and there is another 60-foot bump near 19.25 before the road falls into Somesville.

Somesville is the most important fueling point on the course. The turn onto Route 102 at 20.1 and the low point near 20.5 are the last flat ground before the course climbs about 75 feet between 21.25 and 22, rolls through Hall Quarry, then climbs almost 100 feet from mile 23 to 24 past Echo Lake. Take a gel at Somesville so it is absorbed by the time the climbing starts. Take your last one in the dip around 22.5 to 23. Anything after mile 24 will not reach your legs in time. The 2025 mid-pack ran the last 10K at almost 11 minutes a mile after averaging about 9:34 through halfway. That gap is the climb, and it is also the runners who arrived at Somesville with nothing left.

From the top of the hill just before mile 25 the road drops about 190 feet in less than a mile, 110 of it in one half mile. It is steeper than anything since mile 4 and your quads have 24 miles in them. Do not open it up until the road flattens near 25.75. The finish on Main Street in Southwest Harbor is flat to slightly up.

Weather on this island changes fast. The normal race-weekend high and low are 54 and 40 degrees, the 8 a.m. start is usually in the mid-40s, and the dew point averages 39, so humidity is rarely the problem. Cold is. Cold blunts thirst, so drink on a schedule. Cold also thickens gels, so pre-tear the tabs and carry them against your skin. The coastal miles on Route 3 and Sargeant Drive can be windy, which burns energy without feeling harder. Rain has fallen in about one year in seven. A five-hour runner is still out past 1 p.m. on a wet, windy day, and the race handbook specifically warns about hypothermia, so a runner who stops eating slows down and gets cold together. At the other end, the record high is 74. Above about 62 degrees, drink water with every gel, take two cups where you can, and bring 300 to 500 milligrams of sodium an hour of your own, because the cup of Gatorade gives you about 70.