Look, I learned this the hard way. Back in '18, I rushed through how to winterize a boat before that first freeze hit Michigan. Figured my covered slip would be enough protection. Big mistake. Come spring, I found cracked exhaust manifolds and a bilge full of antifreeze-contaminated oil. $2,700 repair. That's why I'm obsessive about getting this right now – and why you should too.
Winterizing isn't about ticking boxes. It's about understanding why each step matters. Water expands when it freezes. Fuel breaks down and gums up. Moisture breeds mold. Fail any point, and you're facing engine damage, ruined upholstery, or electrical nightmares. Let's break this down without the fluff.
What You'll Actually Need (No Overpriced Kits)
Don't buy those "all-in-one winterizing kits." They're 50% stuff you don't need. Here's the real shopping list:
| Item | Specific Products I Use | Why It Matters | Cost Range |
|---|---|---|---|
| Fuel Stabilizer | Sta-Bil 360 Protection (the blue one!) | Ethanol fuel turns to gunk in 60 days. This keeps injectors clean | $22-$30 per 32oz |
| Non-Toxic Antifreeze | Star brite -50°F Pink RV/Marine | Protects plumbing without poisoning water systems | $5-$8 per gallon |
| Engine Fogging Oil | CRC 6-26 Engine Stor | Coat cylinders to prevent rust during humidity shifts | $10-$15 per can |
| Moisture Absorbers | DampRid Hanging Moisture Absorber (4-pack) | Fights mildew smell – trust me, you want these | $15 for cabin size |
| Battery Tender | NOCO Genius5 (5-amp) | Dead batteries cost more than maintainers | $55-$65 |
Pro tip: Buy antifreeze in bulk at Tractor Supply. Same stuff as marine stores, half the price. And that Sta-Bil? Worth every penny. Saw my neighbor rebuild carbs after skipping it.
Engine Systems: Where Most People Screw Up
The engine is where winter kills boats. Two critical rules:
Never just drain and hope. Always replace water with antifreeze.
Never stabilize fuel by pouring into the tank. It must circulate.
Never stabilize fuel by pouring into the tank. It must circulate.
Outboard Motors (Yamaha, Mercury, etc.)
Raise that motor vertically. Seriously. Any tilt leaves water trapped in the lower unit. Ask me how I know...
- Fuel Treatment: Add Sta-Bil DIRECTLY to your gas tank (ratio: 1oz per 2.5 gallons). Run engine 10 mins to circulate.
- Fogging: With engine running, spray CRC 6-26 into air intake until white smoke pours out. Then kill ignition.
- Flushing: Attach earmuffs, run fresh water. Disconnect fuel line, let engine die from starvation.
- Antifreeze: Pour -50°F antifreeze into flush port until pink exits prop hub.
Inboard/IO Engines (Volvo, Mercruiser)
Raw water system first:
- Drain block plugs (usually 2-4 on sides). Catch greenish water in pan.
- Remove thermostat housing - lets antifreeze flow freely.
- Connect antifreeze kit to intake hose. Run engine until pink exits exhaust (takes 8-12 mins).
Oil change now? Absolutely. Acidic contaminants accelerate corrosion. Use Shell Rotella T4 15W-40.
Plumbing Nightmares (Fix Before They Happen)
Burst pipes sink boats from the inside:
Live-Aboard Trick: Pour vodka into head bowl after antiflushing. Prevents rubber seals from drying out.
- Freshwater System: Drain tank via spigot. Open all faucets. Blow air through lines with shop vac. Pump antifreeze until pink at every tap.
- Head & Holding Tank: Flush with freshwater. Add 2 gallons antifreeze directly into bowl. Pump until pink exits through-hull.
- Air Conditioning: Suck antifreeze through intake until discharge runs pink. Costs less than replacing coils.
Interior: Stop That Mildew Smell
Ever opened a boat in spring to find fuzzy cushions? Avoid it:
- Remove ALL fabrics: life jackets, towels, bedding. They hold moisture.
- Clean fridge/freezer with baking soda. LEAVE DOORS AJAR.
- Place DampRid buckets in cabins and bilge (change mid-winter if possible).
- Rub Armor All on vinyl seats – prevents cracking (don't do floors, makes them slick).
My rookie mistake? Leaving a vinyl shower curtain folded under the sink. Found it fused into a plastic brick.
Covering & Storage: More Than Just a Tarp
Shrink wrap vs canvas? If storing outdoors, pay for shrink wrap. That $300 saved me replacing rotted teak decking last year.
- Frame First: PVC pipes beat wooden 2x4s (won't rot). Leave 18" air gap above deck.
- Ventilation: Install 2 V-vents near bow/stern. Stagnant air = mold buffet.
- Batteries: Disconnect NEGATIVE terminals first. Store on wood (concrete drains charge). Hook to NOCO tender monthly.
For trailered boats: Block frames, don't rest on tires. Release tongue weight or leaf springs sag.
Costly Mistakes I've Made (So You Don't)
| Mistake | What Happened | Fix Cost |
|---|---|---|
| Forgot cockpit drain plug | Water pooled, froze, cracked fiberglass sole | $1,200 |
| Used automotive antifreeze | Ethylene glycol poisoned freshwater tank | Full system flush ($850) |
| Ignored outboard tilt | Trapped water shattered gear case | $1,900 |
Your Top Winterizing Questions Answered
Can I skip winterizing if I'm in Florida?
Only if you'll use the boat monthly. Otherwise, fuel still gums up, mildew grows, and rodents chew wiring. Do a "light" version: stabilize fuel, add DampRid, cover.
How long does winterizing take?
My 28-footer takes 6 hours solo. Budget:
- Engine: 2 hrs
- Plumbing: 1.5 hrs
- Cleaning: 1.5 hrs
- Covering: 1 hr
Should I run antifreeze through my raw water washdown?
Yes! That forgotten hose under the gunwale will split. Pump until pink water sprays out.
Is shrink wrap really worth it?
If snow load exceeds 6", absolutely. That $400 wrap saved me $7k in deck core replacement after a heavy winter. Cheaper than a new bimini.
Final Reality Check
BoatUS says freeze damage claims average $10,000. Take one weekend. Follow this guide. When April comes, you'll turn the key instead of writing checks. That first spring cruise with everything working? Priceless.
Got horror stories or tips? I read every comment below. Let's save each other some grief.
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