The Stanowar is the name given to Stan Pines' boats; in different occasions, there are at least two boats given with similar names.
In Season 1, Stanowar is an old, worn-out, hole-filled fishing boat. In Season 2, there was an old wreck Stan and Ford Pines, who were a child, found on Glass Shard Beach, New Jersey, and then they gave it a makeover.
When they were a child, Ford and Stan found the original boat wrecked on Glass Shard Beach and decided to reconstruct it, with the intent to sail it around the world, and Ford came up with the name "Stan o' War". The twins built the boat throughout their childhood and adolescence; however, their dream never came to fruition, following Stan being cast out from his family and Ford going to college.
The second Stanowar was in Stan's possession for quite some time, and he had planned to go fishing with Dipper and Mabel for a "family bonding day." When Stan is untying it from the dock, in preparation to go fishing, Dipper and Mabel ask Stan if they can use it in their hunt for the Gobblewonker instead. Afterwards, they decide to search with Soos on his boat. Stan goes about the day in solitude, annoying many other fishers.
After Dipper, Mabel, and Soos believe that the alleged monster was just Old Man McGucket in a giant robot, they ask Stan if they can come aboard since their ship has been destroyed. Afterwards, a series of photos of the four enjoying themselves in the boat is shown, and finally Dipper and Mabel relaxing as the group drives off the lake.
The Stan o' war was a small old yacht that had washed up on Glass Shard Beach. It was incredibly dilapidated when Stan and Ford found it, but they were able to fix it up over the years, writing the words "Stan o' war" on the side.
The Stanowar is an old, rickety wooden motorboat. It's got a patched up tarp, a leaky bottom, and a smoking engine. The side of the boat has the word "Stanowar" written in crooked black writing.