Yamaha 4-Stroke Outboard Spring Maintenance Checklist

When warmer weather arrives as spring approaches, that’s your cue to start preparing your Yamaha 4-stroke outboard for boating season. Before you head for the boat ramp, there’s a bit of spring maintenance to be done to your outboard. 

If you winterized your 4-stroke motor before putting it into storage, much of the work should already be done. Nevertheless, if you want your Yamaha 4-stroke motor running at its best when it returns to the water, run through this Yamaha outboard spring maintenance checklist before getting it back out there.

Yamaha 4-Stroke Outboard External Spring Maintenance

Inspect your outboard with the covers off, especially the lower unit, for any scratches or scrapes you missed when winterizing it.

1. Remove any corrosion, and prime and repaint as needed.

2. Wash and wax the top cowling and lower unit. A good coat of marine wax will protect the paintwork and the fiberglass, as well as make the outboard look good.

Yamaha 4-Stroke Powerhead Spring Maintenance

Remove the top cowling, and give the powerhead a thorough inspection.

3. Look for any nesting wildlife such as rodents, birds, or insects and remove them.

4. Check the engine oil. You should’ve changed the oil when you winterized the outboard, but if you didn’t, now is the time to replace the oil and oil filter. If you changed the oil when winterizing, check that the oil level is still correct. An increase in the oil level could indicate that water has entered the system, which means you’ll need to drain and replace the engine oil.

5. Check all hoses for any signs of leaking, cracking or bulging, or that appear worn at their connecting points, and replace any that are. Inspect the hose clamps, and replace them if they’re corroded or loose.

6. Check the electrical wiring for wires that have been gnawed by rodents, that are bent or kinked, or have corroded connections, and replace any as needed. Check that all wire connections are secure and free of corrosion.

7. Remove the spark plugs, then clean them and check the gap between the electrodes. The start of a new boating season is a good time to replace the spark plugs, but do so only after you’ve run the outboard and cleared out any fogging oil you may have used during the winterization process.

8. Consult your Yamaha 4-stroke outboard’s user manual to see how often the fuel/water separator filter and any other fuel filters should be replaced. If you haven’t replaced the fuel filters since last spring, replace them now.

Yamaha 4-Stroke Lower Unit External Spring Maintenance

Once the powerhead maintenance is complete, it’s time to service the lower unit.

9. Inspect the water intakes, and clear out any debris or marine growth buildup within them as necessary.

10. Inspect the prop exhaust for nesting wildlife, or any debris or marine growth buildup from the previous year’s boating season. Clean out the exhaust if necessary.

11. Check the propeller for damage, distortion, and pitted or corroded blades. Ensure the prop nut is tight and the nut’s cotter pin is in place. Replace the propeller if it’s damaged or excessively pitted.

12. Check the zincs/anodes. If they have corroded beyond 50% of their original size and mass, they should be replaced.

13. Check the lower unit oil. You should’ve changed the gearcase oil as part of the winterization process. However, after months of inactivity, the oil may have settled and require a top-off. If the lower unit oil wasn’t replaced during winterization, change it out now.

Yamaha 4-Stroke Lower Unit Internal Spring Maintenance

Internal maintenance for the lower unit may not be necessary at this time. Refer to your Yamaha 4-stroke outboard’s owner manual to see how often the water pump impeller needs replacing.

14. Impellers typically last a couple of years, but if you can’t remember when it was last replaced, or you know it’s been a couple of years, replace it now.

15. If you’re installing a new impeller, inspect the water pump housing and replace any worn parts.

16. Inspect and replace any zincs or anodes that have corroded beyond half of their original size and mass.

Yamaha 4-Stroke Electrical Power & Fuel System Spring Maintenance

The electrical and fuel systems are essential to your outboard's performance.

17. Inspect batteries for leaks and corrosion. Look for deformities such as swollen sides, which indicate that the battery needs replacing. Marine batteries have a life expectancy of about three years, so be prepared to replace them even if they pass a visual inspection. 

18. Charge any batteries, clean their terminals, and reconnect the wires. Check that the connections are tight, and protect them with a coating of dielectric grease. Make sure the battery tray or tie-down straps are tightened securely.

19. If your outboard relies on an external fuel tank, inspect the outside of the tank for damage, cracks and leaks, and replace it if necessary.

20. Check the fuel by disconnecting the feed line from the outboard, and using the primer bulb to collect a fuel sample. Inspect the sample for water, debris or other contaminants, and drain and replace the fuel if necessary.

21. Inspect the fuel bulb and feed line for cracks, wear or leaks, and replace them if necessary.

22. Inspect all the fuel lines running between the tank and the outboard for cracks, bulges, kinks or damage, and replace them if necessary. Make sure all the fuel line clamps and connections are secure and free of leaks. Replace any corroded or loose clamps.

Yamaha 4-Stroke Spring Engine Flushing and Running

You should’ve flushed your Yamaha 4-stroke outboard’s motor as part of last year’s winterization, but it doesn’t hurt to do it again after several months of storage.

23. Use an engine flusher to run your outboard and check that you’re getting a good flow from the tell-tale.

24. Check that all the gauges are functioning, and that you have a good voltage reading.

25. Turn off the motor and allow it to cool. Then, recheck the engine oil and lower unit oil levels, and top them off if necessary. If you’re planning on installing new spark plugs for the boating season, now is a good time to do it.