Sign up to get specials, discounts and boating tips and tricks
*You can unsubscribe anytime
New customers get 10% off
Boat Winterizing Guide
Free guide
Winterize before the first freeze
Water grows about 9% when it freezes, and in BoatUS freeze claims more than three quarters were cracked engine blocks or exhaust manifolds. Pick outboard, sterndrive or inboard, then check items off as you go.
About 9%. BoatUS puts the force in the tens of thousands of psi. In ten years of BoatUS freeze claim files, more than three quarters were cracked engine blocks or exhaust manifolds. More below
Almost full, with a little room left for expansion. Add a marine fuel stabilizer first, then run the engine with a cooling water supply so treated fuel reaches the whole fuel system. More below
No. Use propylene glycol winterizing antifreeze made for marine and RV water systems (usually pink). Car coolant is usually ethylene glycol, which BoatUS calls effective but highly toxic. More below
Out of the boat, and somewhere you will find them in spring. Write down every plug you pulled and every seacock you closed, and leave that list at the helm. More below
Check your engine manual first.
Engines differ, and so do their winterizing procedures. Get the steps from your owner's manual or dealer and do them in that order. This guide is a reminder list, not a substitute. If you are not sure, have a qualified marine technician do the job.
Why it matters: water expands about 9% when it freezes, and BoatUS puts the force in the tens of thousands of psi. In ten years of BoatUS freeze claim files, more than three quarters were cracked engine blocks or exhaust manifolds. Warm climates are not exempt: many southern claims were boats that were never winterized, or relied on a heater that lost power.
1. Fuel
Gasoline enginesDiesel owners: follow the engine maker's fuel storage guidance.
Inboards pull raw water through the engine, and BoatUS prefers circulating antifreeze for them. Typical items your manual will cover:
Engine mounted raw water pump? The Better Boat Winterizing Kit is not suitable for that setup.
5. Water systems
Right antifreeze only. Use propylene glycol winterizing antifreeze made for marine and RV water systems (usually pink). Automotive coolant is usually ethylene glycol, which BoatUS calls effective but highly toxic. It never goes in freshwater plumbing or the raw water side. Buy enough of the right kind before you start.
Outboard Motor Water MuffsDouble sided flushing muffs for compatible outboard and I/O enginesView productSee current price at betterboat.com
Round Boat Motor Water MuffsFor circular intake openingsView productSee current price at betterboat.com
Rectangle Boat Motor Water MuffsFor wider, flatter intake openingsView productSee current price at betterboat.com
Boat Wash Sprayer Flusher and Boat Engine Flush KitA hose connected sprayer with Mixture and Water Only settings that can be used with boat muffs or motor...Check fit on the product pageView productSee current price at betterboat.com
De-Salt Concentrate Salt Remover and FlusherA salt remover concentrate for engines with compatible flushing systems.Check fit on the product pageView productSee current price at betterboat.com
Boat and RV Winterizing KitA gravity flow setup with a 5 gallon antifreeze tank, T connector, valves, clear reinforced hose and...Check fit on the product pageView productSee current price at betterboat.com
Four Pack Boat Dehumidifier Hanging BagsHanging moisture absorber bags with a built-in hanger and a collection bag that holds the water pulled...View productSee current price at betterboat.com
Boat Dehumidifier ContainerA disposable moisture absorber container that traps excess moisture in small enclosed spaces.View productSee current price at betterboat.com
Boat Cover Support PolesTelescoping aluminum poles, 23.5 to 56 inches, that lift the cover so water and leaves are less likely...View productSee current price at betterboat.com