Spring Boat Dewinterization Checklist

by John (JB) Bernier

Spring has sprung and it’s time to put your boat back in the water. Thank Neptune the winter is over. This year I’m going to wake up my boat myself and save some money. But where to begin?  How do the pro’s do this seasonal service? Should I even attempt this?  Will it end up costing me a lot more money?

All very good questions and due to the many styles of propulsion and vessel systems, you should read up using your specific owners or service manual. This will be your first step.

Your spring prep is directly related to the comprehensive winterizing of your engine and boat systems. Basically the more you do or have done for winter layup the better your chances in reducing “Sit-itis.” This is the insidious boat disease that happens, when systems that worked in the fall now do not.

Charging and cleaning your batteries is a good way to start your boat dewinterization checklist.
Charging and cleaning your batteries is a good way to start your boat dewinterization checklist.

Items that should have been completed prior to winter storage:

  • Engine oil & filter changed
  • Fuel filters replaced
  • Fuel tank stabilized (filled or empty)
  • Outdrive or lower unit oil changed
  • Outdrive unit removed for inspection and/or servicing
  • Battery serviced, removed and charged for the winter season
  • Battery cleaned, fully charged and cables removed, wire tied and marked as positive and negative leads if left in boat
  • Lube shifting cables and steering systems
  • Shrink wrap or boat cover with large vents, to prevent mold for forming inside the cover.

That being said, let’s begin our spring prep. Charge all batteries and install them, clean the terminals and cable ends. Replace the wing nuts with stainless steel lock nuts to prevent the cables from loosening up. Coast Guard regulations require that batteries be properly secured and battery posts covered.

Now that the batteries are in place, inspect and check operation of all electrical items and electronics. Test all helm and cabin switches and note items that are not working properly. A test that should always be performed would be to turn off the battery switch (if equipped) and ensure the automatic bilge pump float switch is working.

If you have water systems onboard you will have to remove the antifreeze first. If antifreeze was introduced into the fresh water tank, it should be flushed out prior to connecting the pump and flushing the water lines. There are commercial products available to disinfect the water system. Follow the directions carefully. Pressurize the system and open each faucet/shower head one at a time until clean water flows. Don’t forget the transom or anchor wash faucets.

Inspecting the engine compartment is a must before turning the key for the first time after a long winter.
Inspecting the engine compartment is a must before turning the key for the first time after a long winter.

Next, go to the engine room or compartment. An owner’s or service manual should be consulted for the locations. You’ll need to check engine oil level, inspect the bilge area for fluid leaks. Also, check the coolant level, the power steering fluid, the transmission / lower unit or outdrive oil. A visual inspection of all fuel lines for external cracking and flexibility should be performed. Engine “seawater pumps” should be serviced every other season to ensure they are in good condition. Also be sure to grease the attaching hardware so it will come off two years from now. If you cannot remember when the pump was done, it is time to service it.

It’s time to move on to the start-up procedure. This would be a good time to read the operator’s manual to understand the proper start procedure. We have many customers that have hard starting engines but it is in the startup procedure not a problem with the engine. If running on the hose, Install the ear muffs or water hook up. Beware: there are some engines where you will need to supply water in more than one location. This will be a very expensive mistake.

Check the control cables/condition/operation. Place the shifter in the neutral position and check the safety/kill switch. NOTE: On any engine with an electric fuel pump, you must  prime the fuel system  PRIOR TO TURNING THE KEY. Dry running an electric fuel pump will severely damage it internally and it will fail – trust us on this one. Also your engine will thank you for  fresh fuel that has been treated to minimize water absorption.

You are now ready to start your engine . When it starts, there should be some smoke that clears from the exhaust. This is the fogging oil from winterizing and will coat the spark plugs. Check for oil pressure if you have a dash gauge, then go to the engine and look for water running from the exhaust or telltale. If you see none, stop the engine and recheck your hose connections. Once water is flowing, run just above an idle speed. Check your dash gauges for operation. In the engine area, be careful and stay away from the engine. Inspect with a flashlight for any for fluid leaks under the engine and listen for any exhaust noise such as loose belts or hoses. Check the steering system for tightness or looseness. Ensure the propeller is clear and shift into forward, neutral and reverse. Listen and feel for anything abnormal. Shut down the engine using the safety stop lanyard (if equipped) to ensure it is working, then turn off the ignition key. Remove it and do one final inspection of the engine area. Raise the engine or drive and listen for any strange sounds from the trim – tilt system. A complete servicing of the ignition system should be performed to ensure the engine is running at its best.

Inspect the trailer and wash the boat. A couple of coats of wax and a new layer of bottom paint will get you looking good for the season.

11 on “Spring Boat Dewinterization Checklist

  1. Kim

    Thank you for sharing this excellent information regarding the dewinterization of your boat. Living in a cold region can wreak havoc on your boat and cause major issues come the warmer weather if you do not handle it properly. For those that are unsure about how to follow these steps, I would like to recommend entrusting your boat to a high quality boat servicing center. No only can they handle dewinterizations, they can store your boat, detail it, maintain and repair it when needed, and much more. So, to those about to enjoy the warm weather this spring and summer, enjoy and make sure your outings are smooth sailing by getting your vessel properly maintenanced.

    If you live in the Deerfield, Florida region and are looking for a place to have your boat serviced, check here – https://marinaone.com/boat-service/

  2. Millie Hue

    Thanks for pointing out that we should do more to prepare the watercraft before the winter season comes. Like you said, we will have fewer issues during the spring when we need to de-winterize it. I guess this is what we lacked that is why we were not able to use the jet ski during the summer season because it has been damaged. Now, we plan to get it repaired and prepare it for winter so that we can finally use it again next year.

  3. Tim

    Why remove and disconnect the batteries? Better to leave them on the boat connected with a battery maintainer charge or a solar panel. I visit my boat periodically and plug in to power to top them off

  4. Alice Carroll

    Thanks for the reminder that new engine oil should be used when using a boat for the first time after the winter. I will be getting a boat motor engine flush soon in preparation to store away my boat for the winter. Maybe I should also preemptively buy new oil so that I wouldn’t forget about it once the spring next year get warmer and warmer.


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