Pre-Winterization Engine Inspection

Thoroughly inspect your boat's engine to ensure proper operation come spring.

October 6, 2015

Before you dig into the detail of winterization on your boat, but after your boat is hauled out, give your propulsion system a thorough inspection. If you spot anything awry, you’ll have plenty of time to replace parts or make any needed repairs over the winter, saving you the hassle next spring when you’re anxious to get on the water. Here are some key areas that warrant inspection on the boat’s drivetrain, be it an inboard, outboard or sterndrive power system.

1. Spark Plugs
Remove the engine spark plugs and clean and re-gap them. Replace them if your owner’s manual says it’s time.

2. Gear Cases
On outboards and sterndrives, remove the propellers and check the lower-unit seal for damage or leaks. Check for cracks in the case itself. Look at the skeg too, to see if it needs a coat of paint. If bent, chipped or snapped off, remove the lower unit and take it to a shop to have a new skeg welded on.


3. Prop-Shaft Seals
Inspect and replace or rebuild this vital component of an inboard’s running gear, if necessary. Look for fishing line on all shaft seals.

4. Propellers
Inspect for damage such as dings or bent blades. If in doubt, ask a prop shop to check them out and, if needed, repair or replace the wheel(s).

5. Prop Hubs
If your outboard or sterndrive propeller is more than five years old, it’s a good idea to have the hub replaced as a preventative-maintenance step during the off-season.


6. Raw-Water and ­Circulating Pumps
Pull these off your inboard or sterndrive and look inside the pumps for wear and tear. Replace or rebuild them, if necessary.

7. Gear-Case Water Pumps
Remove sterndrive and outboard lower units and replace the water pump. It’s cheap insurance. Since it’s off, this is a good time to have the gear-case pressure- and vacuum-tested for leaks.

8. Engine Zincs
Replace them if they are more than 50 percent gone. Also check the zinc ground cables because these can corrode or break.


9. Fuel Lines
This includes vent lines, fuel-line connections, fuel-tank connectors, selector/shut-off valves and primer bulbs. With rubber lines, replace any that are more than five years old. Any upgrade should meet the latest evaporative emission standards.


10. Water-Separating Filter
While winterization dictates a fresh water-separating fuel filter element before the boat goes into storage, don’t forget to inspect the filter head too, especially if it is a painted aluminum version. As the paint ages, it can slough off the mating surface with the filter, allowing the aluminum to corrode and create air leaks in the fuel system. If the filter head is less than pristine, replace it now.

11. Secondary Filters
Most outboards have one or more secondary filters under the cowl. Check your owner’s manual to see if you’re due for new ones.


12. Battery Connections
Pay particular attention to connections between the engine and battery. Make sure the connections are tight and free of corrosion. If the battery cable feels stiff or brittle, the wires inside the insulation might be toast. Replace the entire cable and brush the connections with dielectric grease. Toss the wing nuts; instead use nylon-locking nuts to secure cables to battery terminals.

13. Cable Steering
Replace the cable if you see any corrosion, a damaged or cracked sheath, or sense any binding or difficulty turning the wheel.

14. Hydraulic Steering
Inspect the hydraulic steering rams and caps. Also, check hydraulic hoses and connectors for wear and leaks. Rebuild or replace system components as needed. Grease the Zerk fittings.

15. Power-Assist ­Steering
Inspect the power-assist pump for ­corrosion, especially around the wires providing electrical power to the pump. Check the fluid level and top off as needed.

16. Sterndrive Bellows
Remove the drive and carefully check the drive and shift bellows for aging, wear, damage or marine growth. If the flexible bellows — which serve in the critical role of keeping water out of the boat — are more than two years old, replace them.

17. Power Tilt and Trim
Inspect the power tilt and trim system on your outboards or sterndrives for corrosion damage or hydraulic fluid leaks around the pump and rams. If you find trouble, have the system rebuilt over the off-season. Grease the Zerk fittings and coat the rams with waterproof grease.

18. Throttle and Shift Cables
Check the insulation for cracks that can lead to corrosion. Make sure the cables operate smoothly and easily. If there’s any binding, install new ones.


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