1981 Ski-Doo Shop Manual Supplement, Page 45Get this manual

SECTION 03 SUB-SECTION 02 (ENGINES )
503 ENGINE TYPE
For service information on the 1981503 engine type, refer to the 1980 Bombardier Snowmobiles Shop Manual section 03-02 (503 Engine type)For service procedure on the folowing itemBottom end

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives