How to Properly Store a Boat for Winter in Missouri

The Meramec River season wraps up by late October for most St. Louis area boaters. What happens to your boat between then and March matters a lot — a properly stored boat comes out of winter ready to launch. An improperly stored one comes out needing expensive repairs.

Step 1: Give It a Thorough Wash

Before anything else, wash the hull, deck, and trailer thoroughly. Remove all algae, lake debris, and road grime. Dried-on contamination can stain fiberglass and corrode metal fittings over a long winter. Wax the hull to protect against UV exposure even during colder months.

Step 2: Winterize the Engine

This is the most critical step for powerboat owners. Water left in the engine block can freeze and crack the block — one of the most expensive repairs a boat owner can face.

1. Flush the engine with fresh water using flush muffs or a flush port
2. Fog the cylinders with engine fogging oil while the engine is running
3. Change the engine oil and gear case oil — old oil contains acids that corrode over winter
4. Drain the water from the engine block, manifolds, and any water-cooled components
5. Remove the propeller and inspect for dings — winter is a good time for prop repairs

Step 3: Fuel System

Add marine fuel stabilizer to a full tank, then run the engine for 10 minutes to circulate it. A full tank prevents moisture from condensing inside and reduces ethanol-related fuel breakdown over the off-season.

Step 4: Electrical and Battery

Remove the battery and store it indoors, or keep it on a trickle charger throughout the winter. A stored battery that isn't maintained will sulfate and lose capacity — or fail entirely. Big River's enclosed units at Eureka will include trickle charger hookups starting in 2026, specifically for this purpose, so you'll be able to leave the battery in the boat and know it's being maintained all season.

Step 5: Bilge, Livewell, and Freshwater Systems

• Drain the bilge completely and leave the drain plug out during storage
• Flush and drain the livewell and any freshwater systems
• Add RV antifreeze to any lines that can't be fully drained
• Clean the bilge with bilge cleaner to prevent odor and mold

Step 6: Interior and Upholstery

Remove all cushions and store them indoors if possible — or at minimum stand them on edge so air circulates and moisture can't pool. Leave storage compartments open slightly for ventilation. Place moisture absorbers (DampRid or similar) in the cabin to prevent mold and mildew during Missouri's damp winter months.

Step 7: Cover It Right

A proper shrink-wrap job or a fitted boat cover keeps moisture out and protects surfaces. If you're in a covered bay at Big River, you have overhead protection from rain and snow — a canvas cover or shrink wrap adds a second layer against moisture and condensation.

Big River's enclosed units at Eureka will include trickle charger hookups starting in 2026 — ideal for keeping your boat battery healthy all winter. Call (636) 441-9888 to check availability on enclosed spaces.