On a recent day in the Edgartown outer harbor, Capt. Kurt Peterson tuned up his guitar and sang an original song, his right leg holding the wheel of his catboat, Tigress, steady while he strummed.

It was a simple song, culminating with the words: “If the best part is the journey, then I’m already there.”

Mr. Peterson said sailing and music go hand in hand in his family. He and his first mate and younger brother Ryan played another tune, this time on banjos.

Tigress was originally built in 1927. — Maria Thibodeau

“We have a family band,” Mr. Peterson said. “My dad plays the bass he made, my grandpa plays the fiddle. Our other brothers play the washboard and my mom plays the spoons.”

For four summers, Mr. Peterson has ferried eager guests around the Island, serving them cheese and crackers and treating them to Vineyard tales and sailors’ tunes.

Thousands have sailed on Tigress, but many more would recognize her (Tigress recently graced the cover of a Vineyard Vines catalog). Her sail features a giant American flag, inspired by the catboat Cleopatra that sailed in the area in the late 1800s. Mr. Peterson and friends hand painted the sail in the backyard of his aunt’s house on the Cape.

“We used a lot of masking tape,” Mr. Peterson said as passengers on a nearby vessel got out their phones to snap photos of the now-iconic American flag sail.

Captain Kurt Peterson, right, with his brother Ryan Peterson. — Maria Thibodeau

Mr. Peterson started his charter company in 2015 in Edgartown with a different boat, called Nantucket.

“I got a lot of flack for that,” he laughed. “But people say it’s bad luck to rename a boat.”

The next year he found Tigress. The 29-foot catboat was originally built in 1927 in Wareham by Charles Anderson. She is meticulously restored. Most of her features, including details like the clam shell sink and faucet pump in the head, and the compass mounted in the cockpit, are original.

“The wood requires a lot of maintenance: sanding and varnishing,” Mr. Peterson said. “I probably spend 200-plus hours per year just on the paint.”

The previous owner, Roger Fuller, financed Mr. Peterson’s purchase of the boat, a gesture Mr. Peterson won’t soon forget. Mr. Peterson will make his final payment on Tigress this summer.

“[Roger] loved the idea of it becoming a charter boat in Edgartown,” he said. “I think he just believed in me.”

Kurt Peterson and friends hand-painted the iconic American sail flag. — Maria Thibodeau

He sees his success as the result of help from strangers. Another man who believed in him was Charlie Blair, the Edgartown harbor master, whom he credits with helping him get established in town. Mr. Peterson has lived on his boat in previous summers, but this year he sleeps in a room in the Edgartown Inn in exchange for working some nights as a security guard of sorts.

“No one is 100 per cent self-made,” he said. “We all have help.”

Mr. Peterson has seen five couples get engaged so far on Tigress, and one couple got married on board (he officiated the wedding).

He admits to being an introvert, but he doesn’t mind spending his days meeting and talking with new people.

“I get to see the best in everyone,” he said. “I get to spend time with them when they’re on vacation with their loved ones.”

The hardest part of the job? Going to Stop & Shop to restock.

“Parking in Edgartown is so hard,” Mr. Peterson said. “I bought a motorcycle just so I don’t have to park.”

Witnessing proposals, officiating a wedding, it's all in a day's work for a catboat captain. — Maria Thibodeau

He makes the trip as seldom as possible. Loaded down with groceries, he rides back to the harbor with a bag of ice balancing on his gas tank.

He knows what he likes: ketchup with everything, particularly potato chips, spending time with his brothers, mixing his own paint for his artwork from linseed oil, turpentine, liquin and powdered pigment.

And he really, really likes sailing. He bought his first sailboat at age 12, and he and his brothers sailed from the Cape to the Island alone as teenagers.

“It was our grandmother’s rationale that we were safer in a boat than in a car,” Mr. Peterson said.

Sailing called to him again in his early twenties, when he quit an office job to sail from New England to Key West. Thirty-one now, he is able to live in touch with the wind, constantly aware of its direction, its force.

“The weather almost dictates my mood in a way,” he said. “When the wind picks up, I feel more intensity, or maybe that’s not the right word.”

“Invigorated?” suggested his younger brother Ryan.

“Maybe invigorated,” said the Captain.

Asked about the future, Mr. Peterson said it won’t look very different from this: summer days gliding around the Edgartown outer harbor and Katama Bay, playing guitar and meeting guests from around the world.

“It’s what I’ve been doing my whole life for fun,” he said. “I’ll keep doing it as long as I’m physically able.”