Using an Outboard Motor in Sub-Zero Temperatures

Keeping an outboard running without damage during sub-zero conditions requires ongoing maintenance on the part of the owner. This includes completing work after each use of the motor, and whenever the outboard is laid up for short periods. Since outboards have to perform in some extreme-cold applications -- from sportsmen in Alaska to research work in Antarctica -- outboard manufacturers test their outboards in cold conditions as part of the design and production process.

  1. Fuel System

    • Gasoline won't freeze the way that water will, but water will condense inside a fuel tank that's stored in relatively warm conditions. When the fuel tank moves to a sub-zero environment, the condensation can freeze in the motor's fuel system, causing ice dams in the lines. Even worse, the water may simply remain in the fuel, diluting it and causing problems with the fuel system. Avoid these problems by adding fuel conditioner to each full tank of fuel, about 1 ounce of conditioner for each gallon of fuel, before you go boating in sub-zero temperatures.

    Overnight Storage

    • Store the motor vertically -- both from front-to-back and from side-to-side -- in a heated area to allow all water to drain overnight, after each excursion. If you store the engine and boat together, position the tongue of the trailer so the engine is straight up and down before you remove the drain plug from the boat. This allows any water that remains in the engine, the pump, the cooling system and the telltale drain to drain from the outboard.

    Gear Case Oil

    • Before the beginning of the cold-weather boating season, open the lubricant drain screw of your motor's lower unit and gear case. Drain a teaspoon of the lube oil and look for a milky appearance -- a sure indicator of water in the gear case. Feel the oil -- pinch a bit between your fingers -- to check for bits of brass or steel. Even if the lube looks good, change it and start the cold-weather season with fresh oil. If the lube oil looks milky, or if you feel bits of metal, take the motor for repair.

    Crankcase oil

    • Change the crankcase oil in the boat before you begin the cold-weather season. The maintenance schedules from most manufacturers call for an oil change once in every 100 hours of operation. Part of the oil change on some motors means draining a water receptacle in the oil filtration system. This may include unscrewing a glass bowl, dumping it and replacing it, or there may be a drain valve on the bowl.