Fuel, engine and water systems, by engine type. Pick your engine, check items off as you go, and let your engine manual decide the steps and the order.
Your checks save in this browser on this device.
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.
2. Outboards
Outboards are designed to drain their cooling water when tilted all the way down. Typical items your manual will cover:
Water on first. Never start an outboard without a water supply. Even a few seconds running dry can damage the water pump impeller.
De-Salt Concentrate Salt Remover and Flusher: a salt remover concentrate for engines with compatible flushing systems. Dilute per the label (2 to 4 oz per gallon of rinse water) and follow its safety directions.
3. Sterndrives (I/O)
A sterndrive has two jobs: the engine's raw water side and the outdrive. Typical items your manual will cover:
Optional gear:
Boat and RV Winterizing Kit: a gravity flow setup with a 5 gallon antifreeze tank, T connector, valves, clear reinforced hose and fittings. Check fit first. It is for engines with the raw water pump mounted inside the outdrive, using the muff type flushing method. It is not suitable for front engine mounted raw water pump systems and must not be connected to raw water pump suction. Antifreeze, motor muffs and any pump adapter are sold separately. Not sure where your pump is? Check your manual or ask your dealer before buying.
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.
Boat Dehumidifier Container: a disposable moisture absorber container that traps excess moisture in small enclosed spaces. Remove the cap, peel the foil, replace the cap.
