Mercruiser Sterndrive Motor Spring Maintenance Checklist

When boating season arrives, it’s time for some spring maintenance for your Mercruiser sterndrive after months in winter storage. 

A bit of service and maintenance work now could save you from frustrating repairs halfway through boating season. Here’s a spring maintenance checklist to run through for your Mercruiser sterndrive engine.

Mercruiser Sterndrive Spring Maintenance - Oils & Lubes

1. Replacing the engine oil and filter should’ve been one of the first things you did when winterizing your sterndrive. However, much can happen over the winter, so check the engine oil to make sure no water has mixed in with the lubrication system. If the engine oil has a grey, milky appearance, moisture has mixed with the oil and you should replace it.

2. The gearcase lube should have also been replaced as part of winterization. Check the level of the lower unit lube and top it off if necessary. If there are signs that moisture has mixed into the gearcase lube, replace it.

Mercruiser Sterndrive Spring Maintenance - Raw & Freshwater Systems

3. Flush the raw water cooling system to remove any water. Use a flusher to thoroughly clean out the cooling system. If you run your sterndrive in salt water, add a salt remover to the flush to dissolve any salt deposits within the motor’s cooling channels.

4. If your sterndrive has a freshwater or closed cooling system, test the coolant to see whether it has enough antifreeze. The antifreeze breaks down and loses its effectiveness over time, so refilling the freshwater cooling system every couple of years is recommended.

5. Check that all hoses are tight and free of leaks. If you find a loose hose, replace both the hose and clamp. Look for worn, cracked or damaged hoses and replace them if needed. 

6. Consult your owner’s manual to see how often the impeller should be inspected and replaced. Impellers circulate cooling water through the engine and typically wear out within a couple of years. If you can’t remember the last time you replaced the impeller, do it now. Inspect the water pump housing and replace any worn seals or parts.

Mercruiser Sterndrive Spring Maintenance - Fuel System

7. Most Mercruiser sterndrives have at least one fuel/water separator filter and one in-line fuel filter. Replace the filter elements of both. Consult the owner’s manual to see if your sterndrive has any other fuel filters that need replacing at this time.

8. If you drained the fuel tank before winter storage, refill it with marine-grade fuel. If you filled the fuel tank before winter storage, check that the fuel is still good. Healthy fuel has a slightly-sweet gasoline smell, while stale fuel has a sour turpentine aroma.

9. Inspect every fuel line for cracking, bulging or any other wear. Look for leaks, especially at connections, and check that all clamps are tight. Replace any worn or loose fuel lines and clamps.

Mercruiser Sterndrive Spring Maintenance - Electrical System

10. Charge the batteries, clean the terminals and reconnect the battery wires. Test that the batteries are holding charge, and protect the terminals and wires with a coating of dielectric grease. Replace any battery that no longer holds a charge.

11. Inspect all electrical wires and connectors. Look for wiring with damaged insulation or corrosion at the connectors and replace them as needed.

Mercruiser Sterndrive Spring Maintenance - Miscellaneous

12. Inspect all anodes and replace any that have lost over 50% of their original size. Consult your owner’s manual to see if your motor has any internal zincs/anodes and how often they should be inspected or replaced.

13. Re-grease all the zerks and fittings with a high quality marine grease.

14. Grease or lube the ends of control cables, and check them for kinks or pinch-points.

15. Inspect the propeller for damage, corrosion or pitting and replace it if necessary. Check that the prop nut is tight and the nut’s cotter pin is secured. Clear away any debris from the prop and check that the prop shaft oil seal isn’t leaking.

Running through this simple spring maintenance checklist helps ensure your Mercruiser sterndrive engine is ready to go for a new boating season. If you need to repair or replace any Mercruiser sterndrive parts, keep Boats.net in mind for the best pricing. Happy boating!