Do You Need to Winterize Your Boat in Northern California?
Updated: Sep 27
If you live within the lower elevations of Northern California, where the temperatures rarely drop below freezing, do you need to winterize your boat?
Technically, the danger zone for your motor is when the average temperature over a 24 hour period is 25 degrees or less. This is rare, but has happened.
In November of 2020, Sacramento's ABC10 issued a freeze warning for the Central Valley, with "some areas down to 25 degrees." ABC10 also reported that these temperatures could be a risk to outdoor pipes.
Because of temperature drops like this, many Northern California boat owners who store their boat in the winter months adopt a "better safe than sorry" approach to boat winterization.
Boat owners who take their boat out all year round don't follow most of the typical winterization procedures, since they are running their engine frequently.
However, if you only use your boat seasonally, winterizing is advisable — if only to prevent other risks that are not associated with freeze warnings.
If you are a boat owner who is used to doing your own maintenance, you will not find it very difficult to winterize your boat. You can find all the needed components for your boat winterization kit online.
Standard Northern California Winterization Tasks
Below is an overview of some typical winterization steps.
Because all boats are different, if you do your own winterization, check your owner’s manual for full instructions and be sure to follow them to the letter.
Fog the motor
One approach to fogging a motor involves mixing a quart of fogging oil with two gallons of fresh fuel in a portable fuel tank.
The fuel tank is connected to the engine and then the engine is run for 10 to 15 minutes. Once heavy white smoke can be seen coming from the engine, the engine has been properly fogged and is ready for storage.
The other approach is to use a spray fogging oil and spray into the carburetors until white smoke is visible. Fogging oil can also be sprayed directly into the cylinders once the spark plugs are removed.
Add stabilizer to the fuel
Add STA-BIL 360 Marine ethanol treatment and fuel stabilizer to your gas.
This will remove water from your gas and keep your fuel fresh for up to 12 months. It uses specialized PEA fuel system cleaning agents.
Flush and drain the engine block
Flushing outboard engines is relatively straightforward. It involves opening all the drain holes and attaching a hose to earmuffs, which cover the intakes.
Flushing an inboard engine is more involved. Here's a good video on flushing a Volvo Penta 5.0 GXI.
Inspect a variety of points
The following points, at minimum, should be checked before you store your boat for the winter:
Preparation for Outdoor Storage
Because of Northern California's mostly Mediterranean climate, some boat owners choose to store their boat outside all year round.
Here are a couple of additional winterization steps for outdoor storage.
Protect exterior boat surfaces
A boat stored outdoors will collect dirt and debris from the surrounding area, so it's important to cover the boat with a good boat cover.
For outdoor storage, a good boat cover is a must. This boat cover is most effective when it is made of a material that can withstand rain and cool temperatures, such as polyester, polypropylene or a cotton/polyester blend fabric. Shrink wrapping is another option.
It’s also a good idea to clean & buff your boat's hull and apply a coat of boat wax before winter storage. This will protect your boat's finishes from winter rain and moisture.
Heat and dehumidify the engine compartment
Some Northern California boat owners with inboard engines put a goldenrod-type dehumidifier in their engine compartment for warmth and moisture control.
This is particularly important during rainy winters that also have occasional below-freezing temperature drops.
Prevent and repel rodents
Mice are the most common critters to inhabit boats that are stored outdoors.
We wrote about a number of ways to prevent mice from getting into your boat — or to repel them if they do happen to get in.
Other Maintenance Tasks
Here are some other maintenance tasks that are sometimes done at the same time as winterization, but not always.
Change the engine oil & filter
If you let your boat sit with old oil all winter, the oil can corrode the bearings. It's a good idea to change the oil before letting your boat sit all winter.
Replace the oil in the lower unit
Your motor's lower unit, a.k.a. gear case, contains about a quart of oil. 80W-90 heavy duty gear oil is common, but the required viscosity can vary based on the brand of motor.
This process involves removing the lower and top drain screws, in that order. New oil is then pumped back in through the lower drain hole.
Grease your engine
You can apply grease to the grease fittings that are associated with turning and tilting your motor.
This is particularly important if you take your boat into salt water.