Dewinterizing Your Boat

April 20, 2020


Thoroughly checking over your boat prior to operating it will help to prevent breakdowns and damage after launching for the season.

If you are not going to do the job yourself, you need to choose a qualified professional to perform these tasks. Be sure to get in writing what they are going to be doing to prepare your vessel for the boating season.

These tips are not intended to be all-inclusive of the steps necessary for spring commissioning. They are intended for informational purposes only. Please consult a professional, boat dealer or marina if you have any concerns or specific questions.


  • Check all engine block and manifold drain petcocks to make sure they are closed and not leaking. Repair or replace as necessary.
  • Check all fluid levels. If they were not changed when the boat was winterized, now would be a good time to change them with fresh lubricant or appropriate fluids.
  • Check belts and hoses for damage. Replace if necessary.
  • Check all hose clamps. Tighten or replace if necessary. Are they double clamped?
  • Change spark plugs and other wearable ignition parts. Use approved marine replacement parts.
  • Check, clean or replace the flame arrester or air filters.
  • Check all electrical connections (including the battery cables) for looseness and corrosion. Clean or replace if necessary.
  • Charge batteries to full charge and have them load tested. Replace if necessary.
  • Turn on all lights. Replace any non-functioning bulbs or cracked housings.
  • Check horn for proper operation. Repair or replace if necessary.
  • Check bilge blower operation and vent hoses.
  • Check bilge pump and automatic float switch. If your boat is not equipped with an automatic float switch, this would be a good time to install one.
  • Check all raw water intake seacocks (if equipped). They should operate freely.
  • If your boat is equipped with a closed cooling system and the coolant was not changed during winterization, this is another opportunity to have fresh coolant installed.
  • Lubricate all moving connections (i.e. throttle, steering, shifting).
  • On inboard engines, check the engine coupler for looseness. Repair if necessary.
  • Inspect the stuffing box or shaft log for the propeller and rudder shaft. Replace or repair, if necessary, to prevent water from leaking in to the boat.


If the outdrive oil was not changed during winterization, now would be the time to change the oil, grease the u-joints, gimbal bearing, and engine coupler splines.

  • Recheck all rubber bellows for deterioration or damage. Replace if necessary.
  • Lubricate propeller shaft splines with appropriate marine grease. Install your freshly repaired propeller, torque the propeller retainer nut to manufacturer’s specifications, and bend the locking tabs to prevent the nut from loosening.
  • Check the operation of the trim and tilt system. Repair if necessary.
  • The raw water pump impeller should be changed every 2 years or if the water temperature gauge reads higher than normal.


  • Reconnect fuel lines.
  • Change spark plugs and have the timing checked.
  • The raw water pump impeller should be changed every 2 years or when the water discharge stream is weak (should be a straight stream).
  • Check the gear case oil. Change it if it was not done during winterization.
  • Grease splines on the propeller shaft with appropriate marine grease. Reinstall your freshly repaired propeller; torque the retainer nut to manufacturer’s specifications; and bend the locking tabs (if equipped) down to prevent the nut from loosening.


  • Recheck the bilges for dirt and debris that may have collected over the winter. Clean if necessary.


  • Reinstall all the items removed for winter storage.
  • Inspect all life preservers, flare kits, fire extinguishers, and first aid kits. Replace or repair as necessary. Your fire extinguishers are to be inspected/certified annually by an “authorized” fire extinguisher examiner. Replace your safety flares if they out-dated.
  • Connect electronics and test for operation.
  • Close all drawers, lockers, and access panels.
  • If you did not remove the cushions for the winter remove them from the boat and allow them to “air out”.
  • Thoroughly clean interior.


  • Check over the entire hull for any gouges, scratches, peeling bottom paint, or blisters. Repair or repaint if necessary.
  • Check all-thru hull fittings for cracks or leakage. Replace or repair if necessary.
  • Repair all damage prior to launching.
  • If the bottom of the hull has protective paint, this might be a good time to remove the old paint and repaint with fresh protectant.
  • Close all seacocks that were opened for winter storage.
  • Clean and wax exterior of hull and hardware.


  • Check all lights for operation, including brake lights and turn signals (have a friend help). Replace all non-working bulbs or damaged housings.
  • Check all wiring and connections for looseness and corrosion. Repair or replace as necessary.
  • Check the frame for bends or cracked welds. Repair if necessary.
  • Check brake linings and actuator (if equipped).
  • Repack all wheel bearings with fresh appropriate marine grade wheel bearing grease and install bearing caps equipped with grease fittings for periodic regreasing.
  • Check all suspension components for damage or wear.
  • Check tire condition, tread depth, and air pressure (refer to tire sidewall for proper air pressure). Watch for weather cracking in the rubber. Trailer tires tend to deteriorate before they wear out.
  • Torque all lug nuts to manufacturer’s specifications.
  • Check condition of winch strap or cable and all tie-down straps. Replace if any damage is found.
  • Check winch operation Repair or replace if necessary.
  • Check trailer jack and stand for damage. Replace if necessary.
  • Check trailer coupler (tongue) and operation of the latch assembly. Clean and grease if necessary.
  • Check rollers or support bunks. Repair or replace if necessary.
  • Check the trailer hitch on the tow vehicle.
  • Check the wiring on the tow vehicle. Repair or replace if necessary.
  • Check the weight carrying capacity of the tow vehicle and trailer. BE CAREFUL NOT TO EXCEED EITHER!
  • If the trailer requires repairs that can not be made with the boat on the trailer, contact a marine repair facility about “temporary blocking” of the boat while the repairs are being performed.


  • Be sure all seacocks are closed (if equipped).
  • Have all dock lines attached and ready for use.
  • Place docking bumpers in position to protect the side of the hull.


  • When the boat is first put into the water, check for any leaks into the bilge. Remove from the water and repair if any leaks are found.
  • Open the seacock (if equipped) for the engine cooling system. Check for leaks.
  • Start the engine and allow it to warm up at idle. Check for any water leaks from the cooling system. If leaks are found or the engine does not operate properly, remove from the water and repair as necessary.
  • Check operation of gauges (i.e. water temp, voltage, oil pressure, etc).
  • Disconnect the boat from the trailer, engage the drive in reverse, and take to the nearest dock to recheck for any leaks. If any leaks are found, remove from the water immediately and repair as necessary.
  • If your boat is equipped with other seacocks open them one at a time and check for any leaks.
  • If everything checks out alright, ENJOY ANOTHER SAFE BOATING SEASON!

These tips are for informational purposes and not intended to be relied upon for use without consulting the procedure that your specific manufacturer or owners manual may recommend. Always follow the manufacturers’ recommendations when performing any maintenance or repairs, or seek a professional boat dealer/repairer for assistance.