Kona

The snowmobile is located at Lamothe's garage, behind the buildings. You will need to find several items:

• Pliers (you should have these already via normal story play).
• Gas Can: in the garage of Bedard House.
• Crowbar: in the garage behind the General Store (needed to break the wood fence past the Lamothe garage that lead to the Secret Project).
• Snowmobile Key: in the Secret Project area, in the shed with the radiator on it (just past the satellite dish). You will need to solve the wheel puzzle to deactivate the electricity on the door.
• Sparkplug: in the mailbox next to the chainlink fence leading to the Lamothe garage.
• Manufacturer's Manual: inside the Lamothe house, on the table.
• Ski 1: On one of the shelves on the Lamothe house front porch.
• Ski 2: In the trunk of one of the abandoned cars in front of the Lamothe house.
• Bench: at the corner of the Lamothe property is a beach chair and umbrella. The bench is on the chair (it's more like a cushion).
• Handlebars: in the Lamothe garage, on a shelf on the right.
• Headlight: there's one on the UFO in the Lamothe garage. The developers also patched in a second one in a box against the Lamothe house next to the outhouse; either one will work and you only need one (if you pick up both, then the unused one will remain in your inventory forever).
• Snowmobile Track: leaning against the wooden wall behind the snowmobile.
• Gas: The gas pump is in the same area as the snowmobile.

After that, it's a simple matter of approaching the snowmobile and interacting with a few points on it to automatically repair it and earn this trophy.

Note that getting on the snowmobile after fixing it will void the Onwards on foot! trophy (even if you just get right back off), so if you're only doing one run of the game, back away after you've gassed it up!