How to Winterize a Direct Drive / V-Drive Inboard Boat (2001 Tigé 21V)

Leaving water trapped inside your inboard engine block over the winter is one of the fastest ways to crack a block, ruin exhaust manifolds, and end up with a massive repair bill before next season even starts.

Whether you’re running a 2001 Tigé 21V Riders Edition or a similar Mercruiser/Indmar V-drive setup, taking an hour in the fall to properly stabilize your fuel, fog your cylinders, and flush the cooling system with marine antifreeze will protect your boat all winter long.

Watch our complete step-by-step video walkthrough below, or follow along with our detailed photo guide right from the shop floor!

📺 Watch the Full Video Walkthrough

🛠️ Tools & Marine Supplies Needed

Before getting started, make sure you have these key winterization supplies on hand:

• ⚓ Inboard Boat Flusher (Fake-A-Lake): Get Yours Here

• ⛽ Sta-Bil Fuel Stabilizer: Get Yours Here

• 💨 Sta-Bil Engine Fogging Oil: Get Yours Here

• ❄️ Non-Toxic Marine & RV Antifreeze: Get Yours Here

• 🧰 Basic Hand Tools & Wire Pick: For removing block plugs and clearing debris.

• 🧽 Shop Towels / Microfibers: For soaking up bilge water.

Step-by-Step Boat Winterization Guide

Step 1: Treat the Fuel System

Before starting the engine, add fuel stabilizer straight into the gas tank.

• Dosage: 1 oz of Sta-Bil treats roughly 2.5 gallons of fuel.

• Calculate your tank level and dump in the appropriate amount so the treated gas can circulate through the entire fuel system during the warm-up process.

Step 2: Hook Up Water & Run the Engine

Inboard engines pull cooling water from under the hull. Never start an inboard boat on dry land without a fresh water supply connected!

1. Position your Inboard Boat Flusher over the raw water intake under the hull.

2. Turn on the garden hose.

3. Start the engine and let it idle for at least 5 minutes. This runs the stabilized fuel all the way through the carburetor, fuel lines, and engine block.

Step 3: Fog the Engine Cylinders

While the engine is idling with water flowing:

1. Remove the air cleaner/spark arrestor.

2. Spray Engine Fogging Oil directly into the carburetor throat.

3. Allow the fogging oil to coat the intake and internal cylinder walls, protecting them against rust during long-term storage.

4. Shut off the ignition and turn off the garden hose.

Step 4: Disconnect and Remove the Batteries

Open up the engine compartment and locate each battery, one on either side of the engine.

1. Two plastic wing nuts hold the cover for the batteries. Locate and remove.

2. Pro Tip: zip tie the battery connectors so you don't miss any when reconnecting in the spring.

Step 5: Pull the Block Drain Plugs

Open up the engine compartment to access the engine block and exhaust manifolds.

1. Locate and remove the engine drain plugs (typically blue plastic thumb plugs or brass plugs—usually 3 per side on standard inboard V8 setups).

2. Pro Tip: Insert a small wire or metal pick into each drain hole. Sediment and sand often settle at the bottom of the block, blocking water from draining out completely even when the plug is removed!

Step 6: Flush & Fill with Marine Antifreeze

Once all raw water has drained from the engine block:

1. Reinstall the drain plugs hand-tight.

2. Pour non-toxic Marine/RV Antifreeze into the main cooling hoses to fill the block.

3. Briefly crack open a lower drain plug until you see solid pink antifreeze coming out. This guarantees all leftover pocket water has been displaced and won't freeze!

4. Re-tighten the plug and top off the system until completely full.

Step 7(The Final Step): Clean & Dry the Bilge

Don't forget the bottom of the boat! Any leftover standing water in the bilge can freeze or cause mildew over the winter months. Use shop towels or microfibers to soak up all remaining water in the engine bay and lower bilge channels.

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