If you are bad at driving the moped like I am, this is how I unlocked it without dying all the time.
1. Pick up the the moped and put it in the boat
a. If you have not found the boat, stand in your garage looking straight out and walk straight from there to the lake along the dirt path. There is a boat at a dock at the end of the path
2. Drive the boat to the dock nearest Teimo's
a. Point the boat towards the island with the cottage, then adjust to the right about 10-20 degrees to miss the island. Drive straight on and this should take you to the dock you need.
3. Take the moped out of the boat
4. Get on the moped and drive it to Teimo's
Go up the dirt path past a house on the right to the main road. Take a left and drive straight. You'll see Teimo's on the left very shortly.