New Shop Located at:
5394 County Road N
Sun Prairie, WI 53590

I/O Winterization Checklist

Winterizing I/Os

  • Add fuel stabilizer (Stabil or equivalent) to fuel tank(s) per directions. It’s always best to top off your fuel tank(s) to prevent condensation over layup.
  • Start and run motor on muffs at high idle (~2000 rpms) in neutral for 15 to 20 minutes. This will warm up the gear lube allowing it to drain faster, and warm up the motor oil so that it can be sucked out.
  • Remove flame arrestor and fog engine with fogging oil. Try to use a full can, and spray into carburetor until motor dies, or turn off the motor immediately after the can is empty.
  • Using an oil sucker, remove oil from motor through the dipstick. If you don’t have a sucker, try to get a shallow drain pan under oil plug, or drain into bilge and out the rear drain plug (not recommended).
  • Drain lower unit gear lube. If gear lube is milky, your lower unit will need to be resealed and pressure tested. Take it to a qualified marine mechanic.
  • Open petcocks or drains on block, manifolds, and risers and drain out all water. If nothing comes out, use an ice pick and poke into holes. Often sediment will restrict the opening, which prevents water from draining. For late model Volvo/Pentas and Bravo drives, also remove hoses going to the raw water pump in the engine compartment and drain.
  • Closed Cooling System Only: Drain heat exchanger and check antifreeze. Do not drain block, manifolds, risers, or power steering cooler unless you are replacing the antifreeze.
  • Remove coolant hoses from thermostat housing that lead to the manifolds and pour in pink RV antifreeze (-50 F) into hoses until you see pink running out of manifold and block drains (usually a half gallon is sufficient).
  • If motor is equipped with power steering and has a power steering cooler (most V-6s, V-8s, and some 4 cylinders), drain it. You may need to remove a power steering coolant hose to do so if not equipped with a drain plug.
  • Close petcocks and/or replace drain plugs.
  • If boat is used in salt water, fill block and risers with RV antifreeze.
  • Reconnect coolant hoses.
  • Replace oil filter.
  • Fill motor with good quality motor oil, normally 4.5 to 5 quarts. Follow manufacturer’s recommendations for oil grade and weight. I normally use Sierra 25W-40 Premium Blend Inboard Engine Oil
  • Fill lower unit with good quality gear lube. For Mercruisers, fill from the bottom drain hole until gear lube runs out of vent hole. Replace vent plug screw first, then drain plug. For OMC Cobras, fill from the center hole on the lower unit just above the cavitation plate until it registers on the dip stick. Always fill with lower unit in a vertical position. Mercruisers normally take 33 oz, OMC Cobras 64 oz, V/Ps 90 oz.
  • Lubricate gimbal bearing (30 pumps) and outdrive pivot points with marine grease.
  • Remove prop and thrust washer, inspect propshaft seal, remove any fishing line, lightly grease prop shaft, and re-install prop.
  • Prior to Storage:
  • Place lower unit in down position. This allows any water in the outdrive to drain out, and prevents the outdrive bellows from taking a “set”.
  • Remove battery, clean surface and terminals, and store in a cool, dry place. Every 30 to 45 days, put battery on trickle charge (< 6 amps) for 4 to 5 hours.
  • Put trailer on blocks and remove tires, or put wood under tires.
  • If covered outdoors, provide ventilation to prevent condensation (this especially important for shrink wrapped boats).
  • If you are particularly ambitious, wash and wax the boat and hull above the water line.
  • Have a beer!


Last Updated: Tuesday September 01st, 2020