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15 Tips for Winterizing Your Boat and Motor

By John Page Williams

Photos by Shutterstock

If you stop boating when the weather gets cold, make sure you put your boat and motor to bed well. Not doing so can mean that come spring, pulling your rig out of storage can bring frustration ranging from hard starting all the way to serious, expensive damage. Winterizing is important for any outboard, but it’s especially important for a modern four-stroke. To get some straight answers, we talked with Roger Smith, the Mercury Master Tech and Yamaha tech and shop foreman at Chesapeake Boat Basin in Kilmarnock. Here are fifteen tips from that conversation and from general knowledge:

  1. First, consider having a brand-certified mechanic go over your whole rig, especially if your outboard(s) is a fuel-injected four-stroke. These complex machines require the same sort of proprietary analytical software as our cars and trucks. The days of the shade-tree mechanic are over.
  2. “Get that bad fuel out of there.” Smith means the engine itself. His standard operating procedure is to run an engine he’s winterizing, even a small one, with aviation gas (available from local airports), or CAM2 racing fuel, both of which stay fresh much longer than regular pump gas (even that without ethanol). “It’s cheaper than a new fuel system,” he said. Mix the winter gas with two-stroke oil (1 pint/6 gallons) to coat the cylinder walls to prevent oxidation and lubricate the insides of the injectors. If need be, buy a three-gallon fuel tank with hose to hold the mixture and feed the engine(s). Run them until all the old fuel is gone, 20 minutes or more, on a flushing hose or at a boat ramp.
  3. Don’t put in any additives. If the engine is an older two-stroke, fog the carburetor(s) with the manufacturer’s recommended spray.
  4. For the fuel tank, “pump it bone dry and start fresh next season or fill it all the way up,” said Smith. If you fill it, stabilize it, preferably with your engine manufacturer’s product. Be sure to mix it correctly—no more, no less.
  5. Change the crankcase oil and gearcase lube. Follow your engine’s owner’s manual.
  6. While you’re on the gearcase, remove the propeller. Check the shaft for fishing line, which can damage the seal at its base. Smear the shaft with a thin coat of the manufacturer’s waterproof grease.
  7. If your propeller blades are bent or nicked, and if the hub is old, consider sending it off for reconditioning. Your tech will be able to recommend a precision shop.
  8. If you run your boat in salt water and/or shallow, murky water with lots of sand and mud, have your tech change the water pump and the thermostat every year (more cheap insurance). If you can afford it, have the tech pull the lower unit every year, even if you always run in fresh water. A bad cooling system will fry your engine, especially if you run ethanol-laced fuel in season.
  9. If the engine has grease fittings around the mounting bracket and lower unit, grease ‘em. Ditto the cable steering system. Once every three weeks over the winter, go out and turn the steering wheel. Check hydraulic systems, e.g., steering and power trim/tilt. Add fluid if necessary (see owner’s manual).
  10. Flush the cooling system. Smith uses a barrel of mildly soapy water. Wash the motor and coat its whole exterior with a water-dispersing spray. The spray is especially good for the engine’s hood and its brand decals. With the hood off, spray the powerhead, but if it’s a four-stroke with an exposed timing belt, absolutely avoid getting the spray anywhere near the belt. He also cautions that if there’s any chance for mud daubers to build nests inside, put a pair of mothballs under the hood.
  11. Visually check everything on the boat, motor, and trailer, especially wiring, control cables, and battery cables. Have them repaired as necessary. Drain plumbing systems like livewells to prevent freeze damage. Tilt the engine down to drain all water from the cooling system and propeller hub.
  12. Charge the batteries (fill first if they need water), disconnect the cables, and turn off all switches.
  13. Fill the trailer tires and spare to spec with air. Check the lights and repair as necessary. Consider jacking up the trailer and placing blocks securely under the axle(s) to relieve pressure on the tires. Spray them with a protective coating. Wire-brush and paint any nicks on the frame. If it’s galvanized, brush, dust, and spray with cold-galvanizing paint. Replace winch and tie-down straps as necessary.
  14. Store the boat under cover, but make sure there is air circulating through it to avoid mildew and mold, just as you would a house.
  15. Check the boat periodically over the winter, especially after heavy wind, rain, or snow. We’ll have a commissioning checklist for you in the spring.

John Page Williams is a noted writer, angler, educator, naturalist, and conservationist. In more than 40 years at the Chesapeake Bay Foundation, Virginia native John Page championed the Bay’s causes and educated countless people about its history and biology.

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  • October 23, 2023