Winterizing Your Boat: A Step-by-Step Checklist
If you keep a boat in a climate that freezes, winterizing isn't optional — it's the difference between launching cleanly in spring and opening your wallet for a cracked block. The job sounds intimidating the first time. It isn't. It's a sequence, and once you've done it once, you'll do it every fall on autopilot.
Here's the step-by-step that covers most outboard and sterndrive boats. Always check your owner's manual for engine-specific steps.
Step 1: Stabilize the fuel
Top off the tank to leave less room for condensation, then add fuel stabilizer and run the engine long enough to pull treated fuel through the whole system. Ethanol-blended fuel attracts water and degrades over the winter — stabilizer is non-negotiable.
Step 2: Change the oil and filter
Old oil holds acids and moisture that will sit against engine internals for months. Warm the engine, drain the oil, swap the filter, and refill. Do this before storage, not in spring.
Step 3: Flush and drain the cooling system
This is the step that prevents cracked blocks. Run the engine on fresh water, then drain every bit of water from the cooling passages. For raw-water-cooled engines, follow up by pulling antifreeze through the system until it runs out the exhaust.
Step 4: Fog the cylinders
With the engine running (or by spraying into the spark plug holes), apply fogging oil to coat the cylinder walls. This stops internal corrosion over the long idle months.
Step 5: Protect the lower unit
Drain the gear oil and check it — milky oil means water intrusion and a seal that needs attention before spring. Refill with fresh gear lube.
Step 6: Disconnect and store the battery
Pull the battery, top off the charge, and store it somewhere cool and dry on a maintainer. A battery left in a freezing boat all winter rarely survives.
Step 7: Cover it right
A breathable cover or shrink-wrap keeps out water and critters while letting moisture escape. Trapped humidity grows mold; a snug, vented cover prevents it.
A quick word on tools
The right antifreeze, fogging oil, and a decent fuel stabilizer make this whole job easier — and using the wrong antifreeze concentration is the most common winterizing mistake we see. If you want our shortlist of what actually works, [browse the winterizing gear in our store](/store).
Winterizing well is what makes spring launch feel effortless. goFrigg can remind you exactly when to start each fall and walk you through every step for your specific boat — [see our plans](/pricing) and never guess at the timing again.
Go plan it, go prep it, go protect it.