Winterizing your boat.

The kids are back in school and Summer is winding down.  Another boating season is coming to an end, in geographic areas that enjoy changing seasons.

Having worked as an insurance adjuster of boat claims over the past 19 years, maybe I can share a few common mistakes I have seen fellow boaters make in the past, when laying up for the Winter.

Remember to remove all foods and freezable liquids from the boat.  Do yourself a favor, and do a thorough Spring cleaning this Fall.  If you have time, put a coat of wax on the hull.  (You’ll thank yourself next Spring.)

The following paragraphs talk about sterndrives (Inboard-Outboard).  But the first paragraph also applies to outboards as well.  Sail boaters will also find some applicable tips, as you read on.

First of all, consult your owner’s manual.  Most recommend changing the lower unit lube on an annual basis.  (Most DIY folks don’t do it.)  If you’re one who runs the lube for more than one season, then, at least drain an oil sample from the lower unit’s lower drain plug, after the unit has been sitting in a vertical position for a few hours.   Oil floats on water.  So, if there’s water in the oil, you should see it in the drained sample.  Look for a clear oil sample with no signs of metal glitter in the oil or metal filings stuck on the drain plug magnet. (Not all plugs have magnets.)  If the oil is “milky” or “brownish-grayish” in color, you probably have a leaking shaft seal.  The unit will need service and an oil change BEFORE freezing weather.  The water must be removed from the unit prior to freezing, to prevent further damage.

Now it’s decision time.  Just how thorough do you want to be in this project?

To do a complete job, you should really pull the sterndrive off.  This isn’t a real difficult task, although I recommend either reading a technical “how-to” article or inviting a friend who has done it before to help with your first attempt.  (To be honest about it, most do-it-yourselfers I know, don’t pull it every year.)  But…..

If you decide to remove the drive, it’s a great opportunity to check several components:  The gimbal bearing and input shaft of the lower unit:  The input shaft (splined drive shaft) is supported by a roller bearing assembly called the gimbal bearing.  The gimbal bearing lives inside the intermediate transom unit of the drive train, which means it is still with the boat after you remove the drive.

With the sterndrive removed, you can roll up your sleeve and reach through the drive shaft boot to the gimbal bearing.  Roll it about with your fingers and see if it rotates without binds or excessive noise.   If all is okay, you’re good to continue.  If the bearing is rusty, or makes grinding sounds and feels rough through a rotation, then it should be replaced.  The gimbal bearing isn’t a real expensive part, but it requires proper tools to replace it; a puller (slide hammer) and a pilot to bump the new one back in place.  (You might want to talk with a service center.)

This is a good time to check and/or replace the rubber drive shaft and shift cable boots.  If the drive is removed, they’re easy to inspect.  Poke at them with your finger, and try to spread the bellows to see the bottom of the pleats.  There should be NO weather checking and/or cracking.  If the rubber boot shows any sign of deterioration, then replace it.  (Most manufacturers recommend annual replacement.)  Some brands of sterndrives require the proper pilot tool to re-install a new boot.

Now, with a flashlight, look all the way through the gimbal bearing at the splined hub, which is bolted to the flywheel of the engine.  The female splined socket should have nicely formed “square” edges on each raised spline.  A worn spline will have worn the squared edges to “pointed tops that will begin to resemble a triangular shape when viewed from the end.

Most folks don’t realize the drive shaft actually slides in and out of the gimbal bearing and hub slightly as the helm is turned.  This movement creates wear on the hub splines.  It’s important to apply a light coating of waterproof grease to the shaft and splines periodically.  (Some intermediate units have a grease zirk or cup inside the boat for this purpose.)  Replacement of a failed hub is labor intensive.

If you removed the sterndrive, you should obtain a new gasket set to replace it.  It’s not expensive and is available from your dealer.

If you didn’t remove the drive unit, you can still check the boots:

To check them, raise the drive to the trailer position and turn the helm fully to one side.  Now with a flashlight, from below, you can see the drive shaft boot; a black rubber accordion bellows tube.  The shift cable and boot can usually be seen protruding through the transom unit, near the pivot points of the sterndrive tilt mechanism.  Of course the shift boot is smaller than the drive shaft boot, but it is also a black rubber pleated tube.  Check it, using the same criteria as with the drive shaft boot: no cracking or weather checking.

A word of caution here:   Don’t try to save a buck by running a weathered boot just one more season.  Failure of boots (shift & shaft) can sink your boat

Another tip regarding outboards and sterndrives, is to store them either in the “down” position, or “bag” the prop shaft area with a plastic garbage bag to prevent rain water from collecting in the exhaust hub behind the prop.  Of course, if you’re storing in a dry building, this isn’t as much of a concern.  The point here is to ensure there is NO water remaining in the exhaust hub.  It will freeze and expand over the winter, and the result can be a cracked gear case housing.  Your insurance adjuster will recognize it as freeze damage, which is almost never a covered loss.

If you store your boat outside, here are a few more tips:

Remember to remove all foods that could attract “critters”.   All animals are going to be looking for a winter home.

Remove the drain plug.  If any rain water or snow-melt gets inside, you want it to run right on through, and not collect in the bilge.  And, along that same line of thought, you should ensure the attitude of the blocking, or highway trailer is supporting the boat in a manner that water will run toward the drain plug, and not get trapped in a low end of the bilge.  If the boat is resting on stands or foam blocks, make sure there are enough to provide proper support.  The keel should be well supported.

Support your winter cover, ensuring there are no low spots that will collect an accumulation of snow and water.  Once the pooling begins, it only gets worse with each passing storm, until it either rips the cover, or creates a very large pool.  (Remember, water weighs 8 lbs./gallon.)

Secure the winter cover well, ensuring it is snug against the hull in all areas.  You don’t want to leave an opening for the “critters” like raccoons and mice to enter.  Also, don’t leave any loose “flaps” that will blow like a flag in the wind.  “Flagging” covers don’t last very long, and re-covering a boat on a cold winter day is not a pleasant task.





First things first:    You should be using a marine grade of gasoline.  This means no alcohol.   If you have been buying gas at the local gas station, then you most likely have a blend of gasoline and alcohol.  If that’s the case, I recommend running it out and/or draining the system prior to winter layup.  The gas and alcohol will separate over long layups, and the alcohol can absorb water (humidity).  What you could end up with in the Spring is a tank of useless fuel.

There are two schools of thought on storing fuel through winter layups:

Some folks like to fill the tank to eliminate the collection of moisture through condensation of heating and cooling temperatures, while others like to empty the tank to prevent the gas from going “flat” over the layup.

There are pros and cons to both sides:  If you store with an empty tank, it is true; the air in the tank could create condensation inside the tank.  But, if you store it full of gasoline, then many times as the temperatures begin to warm  in the Spring, the fuel inside expands and runs out the over flow; a fire hazard and also a waste of money.

I typically stored my boats with about ¾ tank of fuel for two reasons.  1)  Sometimes the gas dock wasn’t up and running in the early Spring, when I wanted to launch the boat.  And 2) I reduced the condensation risk.

My reasoning was the tank had room for expansion, as it was only ¾ filled.  And I reduced the amount of air inside the tank to collect condensation.  There are additives on the market now a days to stabilize the gasoline for extended storage.


How about the engine?

This one gets a little tricky.  I can only tell you what I’ve done in colder climates.  The bottom line is you have to either get ALL the water out of the engine, hoses and heat exchangers, or replace it with antifreeze.

My line of thinking was similar to the guy who wears a belt AND suspenders !

I always did my own winterizing in Central Illinois, where it would typically hover around zero, or a bit below for a week or so each year.  It was indeed cold enough to damage an unprotected engine and plumbing system.

My procedure was to start with a warm engine, ensuring the thermostat was open.  (This can be done by running on a garden hose and “ear-muffs” for a while, until the temperature gauge at the helm indicates a warmed-up engine.) Then I would drain EVERYTHING related to the cooling system of the engine.  Open petcocks, remove drain plugs, and hoses.  (Always use a small wire to probe into each drain hole to ensure there isn’t some debris creating a blockage.)

I used RV antifreeze to winterize, because it wasn’t harmful to the fish, when I started the boat in the Spring.  I would then find a way to introduce the antifreeze into the engine’s cooling system intake.  A simple method for an outboard or I/O is to make up a short piece of garden hose connected to the service ear-muffs.  Put a funnel into the end of the hose and begin pouring the antifreeze into the funnel as the engine idles.  The engine will draw in the antifreeze, filling the cooling system.  Somewhere near the end of the 2nd gallon, you will see the pink antifreeze coming out the exhaust.  This tells you the system is filled with antifreeze.

Now, drain everything again.  (This is the suspenders part.)

No guarantees from me, but, I’ve done it for years, and it has always worked for me.


A charged battery will not freeze in winter weather.  A dead battery will freeze and break the case, causing the internal acid to leak out.  It used to be standard procedure to remove the batteries over the winter to prevent freezing, although today, most folks leave them in the boat.

At the very least:  Ensure the batteries are fully charged, when the boat is laid up.  If in doubt as to their ability to hold a charge, then I recommend removal during the freezing season.



Start by emptying the tanks; Fresh water tank and black water holding tank.

Now, disconnect the fresh water supply line, at the fresh water pump.  With a piece of hose, make up a funnel-feeder that will enable you to pour RV antifreeze into the pump intake port.  Turn on the pump and begin opening the water faucets one at a time until you see pink.  Don’t forget to flush the head until it runs pink as well.

If your boat has other water pumps feeding live wells, or ballast tanks, then treat them as well.

I always poured a little antifreeze down the sink drains, just in case there were any low spots, holding water.

If your boat has a shower, with a sump, be sure to pump it dry and/or fill it with antifreeze, making sure the pump has antifreeze inside as well.


If your boat has an air conditioner:

Do the same as above with the funnel and RV antifreeze, feeding the A/C raw water pump this time, until you see pink at the discharge opening. (Usually above the water line on the hull topsides.)


Look over the prop.  If it needs service before the next season, then do it now.  If you take it to a shop in the off-season, you will avoid delays in the Spring rush; and you may get a discount because the shop is looking for off-season work.


  • Do what you can to keep the rain and snow from accumulating on or in your boat.
  • Remove anything of high value that can be easily carted off by thieves.
  • Remove all freezable items, and protect the power train and plumbing.

Some boaters leave the boat’s cabin door unlocked over the winter layup.  The theory here is a thief will get inside no matter what you do, if he wants to.  If the door is locked, then he will break something in the process.  The negative side to this theory, is some insurance policies require you to lock the door.

CHECK YOUR BOAT PERIODICALLY.  Ensure the cover remains secure, and all is well.

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