Getting Your Mercury Engine Ready for the Season

Getting Your Mercury Engine Ready for the Season Your boat is loaded and you, your family and friends are looking forward to a day of fun on the water. The boat is launched and everyone is excited, but . . . your engine fails to start. We have all, unfortunately, been there. One of our guiding missions here at PartsVu is to help you to maximize your fun on the water, and to reduce the stress of mechanical problems.

We prepared this simple engine maintenance checklist to help you to prepare your boat for spring breakout. Hope you find it helpful.

For All Mercury Outboard Engines

  1. Refer to your owner’s manual for specific instructions on your engine.

  2. Add Mercury Quickleen to your fuel tank and top off the gas. There are differing thoughts on filling the fuel tank before storage. Whatever your approach, good fuel treatment at the start of the season is important. PartsVu recommends Quickleen with every fuel up.

  3. Check the fuel system connections for leaks and the fuel hoses for softness or brittleness. Replace if needed. Prime the fuel system using the primer bulb pump.

  4. Check the grounding cables on the engine mounting bracket and batteries for breakage or corrosion. Clean them if necessary.

  5. If using wet cell batteries, check the battery water level per manufacturer spec. Charge batteries and check date stamps. The average lifespan is 3-5 years.

    Looking for a new battery charger?

    Boat Engine Outboard Engine Diagram


  6. Check your propeller. Remove the propeller, use 2-4-C Marine Grease for the shaft/spline, and check that the lower unit seal is not compromised.

  7. Inspect for any leaks out of the lower unit from the drain screws or prop shaft. Replace gear lube as needed

  8. Steering – move the steering wheel, checking for free movement through the full range.

    • Mechanical Cables – grease the ends of the cable where it connects to the helm and to the engine.

    • Hydraulic – check for any hydraulic oil leaks, examine the hose, especially hoses by the engine and cylinders – add marine hydraulic steering fluid as needed.

    • Power Assisted Systems – check for any leaks, examine hoses, and check/fill reservoir.

  9. If your outboard is equipped with a power trim and tilt system, check that its operation is functioning as it should. Look for any fluid seepage around the piston seals and reseal/replace as needed.

  10. Test run the engine before launching the boat, burning off any fogging oils or other storage elements introduced into the engine. This provides an opportunity for you to check all the gauges, electronics/navigation systems, examine for leaks and verify overall operating functionality before your first trip out on the water. When running your engine out of water, the team at PartsVu recommends using engine flushing earmuffs for the lower unit and following all owner’s manual suggested procedures and safety precautions.

For the Mercury Four Stroke & Verado

  1. Check the engine oil level by tilting the engine vertical and allowing 5 minutes for the oil to fully settle. Pull dipstick and confirm oil level. Black, burnt, or milky oil should be replaced and may indicate bigger issues.

  2. Check the primer bulb for proper functionality and the condition of the bulb and fuel lines.

  3. Inspect under the cowling for any animals who may have made your engine home during the off season. Yes, this happens more often than you would think!

  4. Look for obvious signs of salt accumulation under the cowling as this would indicate a leak. If no salt is found, apply a coating of anti-corrosion spray.

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Mercury Fourstroke Outboard Boat Engine

For the Mercury Optimax / EFI

  1. Run the engine, burning off any fogging fluids and testing for proper operation of the engine.

  2. Check two stroke oil reservoir and verify there’s plenty of oil on hand for operation. Inspect tank hold down brackets and fill hoses.

  3. If you mix the oil in the gas, be sure to have enough oil on hand for refueling and add Mercury Quickleen at fill up.

  4. Check the primer bulb for proper functionality and the condition of the bulb and fuel lines.

Mercury EFI Boat Engine

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For the Mercruiser Inboard / Outboard

  1. Check the engine oil level by pulling the dipstick. Black, burnt, or milky oil should be replaced and may indicate bigger issues.

  2. Check/refill the drive lube reservoir. Replace cap if necessary. The reservoir sits on top of the engine block and is noted.

  3. Check the power steering fluid reservoir, refill as needed.

  4. Verify that the trim and tilt operation of the lower unit works efficiently and smoothly. These outdrives take extra abuse and need careful inspection during your breakout. The seals, bellows, and cables could have been compromised while in storage. Replace them as needed.

  5. Run the engine, burning off any fogging fluids and testing for proper operation of the engine.

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If you follow these simple steps, your Mercury engine should be ready for the start of the season. For additional maintenance best practices, check out our other engine-specific and easy to read blog articles. Let us know in the comments section if you have any more concerns about your Mercury engine.


For lifestyle, how-to, gear & technology and inspiration, check out Mercury Marine’s blog – Dockline.

Topics: General Repair, Care & Maintenance,Mercury Maintenance