The Larson snowmobile was produced for a short period in the late 1960s. Larson Boat Works, the manufacturer, had purchased a major interest in Polaris Industries, manufacturers of the Polaris line of snowmobiles in 1965, as well as Northland Ski Manufacturing Company and C.A. Lund Company, makers of “Northland” water skis, snow skis, and hockey sticks. In 1966, with a thriving business, Larson Boat Works sold its share in Polaris to produce their own line of snowmobiles.
The first Larson snowmobile rolled off the assembly line in September of 1966 for the 1967 model year. That first sled is on display at John Monahan’s Boat Works Museum in Little Falls, Minnesota, in its birthplace. Larson Boat Works, however, found it impossible to compete with already established snowmobile manufacturers and production ended shortly after it began.
Featured below is a 1967 Larsen Eagle model. It ran a 372 cc JLO engine.

Photo credit: Linda Aksomitis. Photo taken in March, 2009, at the 6th Annual Vintage Snowmobile Round-Up in West Yellowstone.
References:
Andreas Jordahl Rhude. (2006) “Larson – Brunswick Boats: Rough Seas.” The Antique and Classic Boat Society Incorporated — BSLOL Chapter. Found January, 2010, at: http://www.acbs-bslol.com/Boatbuilders/LarsonBWPt3.htm