The Outboard Expert: How to Avoid Duck-Hunter’s Freeze-Up

Hot tips for late-season outboard operation.

18th October 2007.
By Staff

Keep your motor tilted down in the water during freezing temperatures to keep the water pump from icing over.

Keep your motor tilted down in the water during freezing temperatures to keep the water pump from icing over.

The duck-hunters working the marsh on the edge of town are banging away at dawn this week, which means the boating season in the upper Midwest is coming to close. Hunters, late-season walleye anglers and leaf-peepers are usually the last folks to leave the water around here, stretching the season well past Labor Day, and even Halloween. Late-season boating can be invigorating, but you’ll want to make sure your outboard and boat are ready to handle the cold. Here are some tips to consider:

Your outboard motor can probably handle more cold than you might imagine. Mercury Marine, for example, rates all of its outboards to operate at temperatures as low as zero degrees, just in case you can still find open water when the air is that cold. And a reason to be out there. If you have a four-stroke outboard, check the owner’s manual for advice on proper oil viscosity for cold-weather operation. Mercury and Yamaha specify 10W30, while Honda prefers 5W30 oil. If you are going to run a lot in cold weather, you might need to change to a lighter-weight oil. And I’d highly recommend that you make sure that oil meets the new FC-W spec for four-stroke marine lubricant. To give that oil a chance to do its job, let the warm up before heading out on the water.

The most common cold-weather outboard problem is something I call “duck hunter’s freeze-up,” which occurs when a hunter tilts up the outboard to keep it out of marsh muck or to pull a skiff ashore. This traps water in the motor, which freezes if the air temperature is low enough. If the water pump freezes up, the rubber impeller vanes may tear apart when the motor is restarted. In an extreme case, the expansion of freezing water could crack the pump housing or even the aluminum mid-section of the motor. When the air temperature is below freezing, always keep the motor in its down position when it’s not running. This will allow all water in the motor to drain to the waterline. Water in the submerged portion of the motor will not freeze. If you pull your boat ashore, try to lift the stern with the motor lowered to drain as much water as possible from the outboard. And before trailering your boat home, lower the motor completely and allow it to drain for a few minutes. If you keep your boat in a slip, leave the motor down in freezing weather.

Ice coating the motor’s steering mechanism can also be a hazard when the temperature drops. Keep the steering tube and swivel tube well greased, and operate the steering through its full port-to-starboard range to clear any ice before you put the motor in gar. Then turn the steering lock-to-lock to after each outing to keep the steering from freezing up overnight.

Many marine techs I’ve talked to do not recommend adding fuel “de-icer” additives to boat gas, especially in area where ethanol-blend gasoline is common.

“Winter fuel blends often contain some alcohol,” says David Greenwood of Suzuki Marine. “Outboards are designed to run on up to 10 percent alcohol fuel blends, but adding more alcohol to the fuel with a de-icer additive can wash the cylinder walls of two-stroke motors free of oil. Excessive alcohol may also damage some fuel system components.”

To keep moisture out of your boat fuel system, install a large water-separating fuel filter and keep your boat fuel tank filled to prevent the formation of condensation.

Freezing water can also damage the bilge pump and livewell pumps on fishing boats. After each outing, pull the hull drain plug and tilt the bow up to allow all water to drain from the bilge. Then run the bilge pump to make sure it is clear of water. Livewell pumps and lines can be hard to drain completely, and it may be wise to avoid using the wells at all in cold weather. If you do, try to drain the system completely after the boat is on its trailer.

Trolling motor batteries that are discharged are also prone to freezing. In very cold weather, pull the batteries and put them in your vehicle for the ride home, and then re-charge them immediately. Water splashing on deck can freeze up the inside of hatch latches. Spray them with a water dispersant like WD-40 before heading out and keep lock de-icer on board to unstick a stubborn latch.

Your bass boat is not an icebreaker. Never attempt to run through ice no matter how thin it looks-it could get a lot thicker in a hurry. Ice is sharp enough to cut through a boat hull, and could tear fish finder transducers and speedometer pitots right off the transom. And consider this-how thick will the ice be when you return? You could become stranded in very cold weather.

Finally, be sure to dress appropriately, always considering the wind chill created by a moving boat. A PFD is a good insulator and should be worn at all times in cold weather. Carry dry clothing on the boat to change into in case someone does fall overboard. A person in soaking wet clothes is a case of hypothermia waiting to happen.


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