Shared with permission from “How to Restore Your Wooden Runabout, Volume 2″, by Don Danenberg.  Don Danenberg added a few updates to the text.  You may see more of his advice on his website page or even join his forum group at 


There are basically two ways to winterize the engine to prevent damage from freezing.  One is to find and open every drain plug in the engine block, exhaust manifold, water pump, and oil-cooler, and drain as much water as possible.  The other is to fill the engine and components with biodegradable antifreeze.  This marine – or RV-type antifreeze is usually pink or blue in color, whichever one your supplier has that offers “corrosion inhibitor“.

The best recommendation is to basically do both.  This should guarantee that there are no pockets of water or over-diluted antifreeze.  Running the engine also allows you to spray fogging oil in the carburetors and warm up the oil so that it can be easily pumped out and replaced.

If your engine has a thermostat, this should be temporarily removed so that complete circulation can ocur.  Some recommend adding a fuel stabilizer to the fuel.  If you do this, add it to the tank before running the engine so that it is spread throughout the fuel lines and carburetor.

Our procedure is as follows:

  1. Provide a water supply and start the engine, run until it is warmed up, and shut off the engine (make sure that the exhaust is not aimed at anything you do not want soot on).
  2. While engine is warm, pump out and replace the engine oil. ( My engine guy recommends replacing the oil in the fall, rather than spring, because oil becomes acidic with use and it’s best not to leave that acidic oil sit in the engine all winter in storage.)
  3. Drain all water plugs in the engine and any component that may hold water, put them back in, and remove any thermostat.
  4. Provide a water supply hose, either directly to the engine-intake hose or the plunger, as mentioned earlier, to a 5-gallon bucket holding at least 3 gallons of full-strength marine antifreeze that includes corrosion inhibitor.
  5. Start the engine and run at a high idle until antifreeze comes out of the exhaust.
  6. Just before you shut the engine down, spray a couple ounces of fogging oil (we use Lubrimatic in a 10 ounce spray can) into the carburetors.  Turn off the engine.
  7. Remove the spark plugs and spray the defogging oil directly into the cylinders.  To protect cylinder walls, pistons, rings, valve guides, and seals, turn the engine over several times. Spray the spark plugs and openings before replacing the plugs.
  8. Disconnect the bilge pump hose at the pump and drain it in case it is still holding water.
  9. Vacuum or sponge any water out of the bilges.
  10. If you are not using antifreeze, remember to drain out the exhaust pipe.  Some of these tip up at the transom and can hold quite a bit of water.  Drive the boat up a steep hill or partially down a boat ramp to do this.  In some locations, it is wise to tape a tin can over the exhaust pipe, or stuff it full with steel wool to keep out mice and squirrels – I’ve seen cylinders filled with walnuts.
  11. The battery should be removed to indoor storage and occasionally given a trickle charge over winter.


It is very important to provide air to all parts of the hull during storage to avoid high moisture content in stagnant air.  This means opening all hatches and tilting forward the seat backs.  Too much air, though, also can be a problem.  If the boat is stored in a very drafty location, winter winds can dry too much moisture from the wood.  Cement floors also can suck moisture out of the air.  If the varnish appears to be cracking and the boat is opening at the seams, you should keep a large pan of water beneath the hull or occasionally hose down the floor.

I store all removable upholstery such as seat backs, seat bottoms, and cushions indoors. This helps to keep the wildlife from nesting in them.  Also, it is better to have a very loose-fitting storage cover, than a tight one.  The cover should be cotton so that it will not hold in moisture.

Thank you, Don Danenberg, for sharing your expertise with the rest of us. Don is a member of the ACBS Water Wonderland Chapter.

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