St Lawrence Engine company

Antique Boat Museum, NY

The St Lawrence Engine Company of Brockville Ontario manufactured basic two-cycle marine engines starting in 1905. The company was in operation till about 1949 with only minor changes to the design, one being a change to aluminium pistons in about 1935. Much more information here. 
This company is not to be confused with the earlier Montreal-based company of the same name that built steam engines and sawmill equipment.