What to Do if Your Outboard Has Been Sitting for a While
Cope Marine Advice: What to Do if Your Outboard Has Been Sitting for a While
Life happens, and sometimes boats sit unused for months — or even years. Whether it’s a seasonal layup or an extended period of 5, 10, or 15 years, a sitting outboard requires careful attention before you hit the water. At Cope Marine, we’ve seen it all, and we’re here to guide you through the steps to safely revive an engine that’s been idle.
1. Remove the Spark Plugs & Oil the Cylinders
Before you try starting an engine that’s been sitting, remove the spark plugs. This gives you a peek inside the cylinders and allows you to inspect for:
Rust
Corrosion
Water damage
If needed, replace the plugs with fresh ones to avoid starting problems.
Next, squirt some fogging oil into each cylinder, then turn the engine over by hand a few times. This lubricates pistons and rings, protecting the engine from scoring or other damage during its first startup.
2. Check the Gear Lube
Water can infiltrate your lower unit during storage, leading to rust or bearing failure.
Remove the drain plug and inspect for water — it will collect at the bottom.
Make sure the gears shift smoothly.
Replace old gear lube with fresh oil and install new seals on the drain and vent plugs.
Doing this before startup prevents costly lower-unit damage and ensures smooth operation.
3. Inspect the Fuel System
Old fuel can lose octane, become sludgy, or accumulate water. To protect your engine:
Disconnect the fuel line near the engine.
Tilt the boat bow-up so water or debris collects at the tank rear.
Avoid running bad fuel through your engine — it can cause serious problems on the water.
If fuel is bad, connect a separate tank with fresh fuel to the engine and prime the lines. Flush old fuel out of the system, whether the engine is carbureted or fuel-injected:
Carbureted engines: Remove carb drain screws and push fresh fuel through using the primer bulb.
Fuel-injected engines: Drain the VST (fuel reservoir) until clean fuel runs out, using the vent or Schrader valve as needed.
4. Check Oil Levels
Depending on your engine type:
4-stroke: Check or replace engine oil. Never start an engine low on oil.
2-stroke: Ensure the oil injection tank is full.
Long-term storage can cause unexpected issues — always confirm your oil reservoirs are full before attempting startup.
5. Charge the Battery
After extended storage, batteries rarely hold a charge.
Fully charge or replace the battery before attempting startup.
Use a trickle charge (2–10 amps) depending on how long you have to charge.
Always ensure the charger is safely connected — avoid leaving cords on flammable surfaces.
6. Start the Engine Using a Hose
Once oil, fuel, and battery are ready:
Connect a garden hose to flush the engine with water.
Use earmuffs instead of running the engine at high RPMs via the flush port to avoid damaging the impeller.
Start and run the engine, checking all systems: steering, trim, and shifting.
Mechanical steering components and cables can seize during long storage, so it’s crucial to test everything before launching.
7. What to Do If the Fuel Is Bad
If fuel has degraded, don’t just add fresh fuel on top. Mixing bad and new fuel can cause poor performance or engine damage.
Use a fuel pump to remove old gasoline safely into containers for proper disposal.
Tip the bow of the boat upward to ensure all old fuel is removed from the tank.
Proper fuel management prevents headaches and protects your engine.
How Long Can a Boat Sit?
There’s no fixed timeline — it depends on storage conditions:
Properly winterized or summarized boats can sit for years with minimal issues.
Boats left outside without protection can suffer freezing, rust, corrosion, or animal damage.
Long-term neglect can destroy lower units, engine components, and interior finishes.
The key takeaway? Proper preparation before storage is essential. If your boat will be idle for more than six months, invest the time to winterize it correctly. It saves money, time, and frustration later.
Final Advice from Cope Marine
Reviving a long-sitting outboard is a careful process — but with the right steps, it can return to reliable operation. At Cope Marine, we recommend:
Inspecting and lubing cylinders
Checking and replacing gear lube
Flushing old fuel and replacing with fresh fuel
Confirming oil levels and filling oil injection tanks
Charging or replacing the battery
Carefully starting and testing the engine
Following these steps protects your engine and ensures a smooth, worry-free day on the water.