Winterizing your boat’s engine is extremely important if you live in cold climates. Here in the Pacific Northwest we can go from summer heat to winter cold seemingly over night. Part three of this series goes over the steps we take to winterize our inboard marine gas engine.

It’s important to remember the reason for winterizing, we want to protect the engine and its systems from freezing, rust and corrosion. It is better to do your routine maintenance at the end of the season rather than beginning as any problems encountered will have lots of time to be fixed in. (Pictures below, click to enlarge.) Special thanks to my hubby Mike for his help on this article! As always, if something doesn’t make sense, talk with your marine engine mechanic.

  • Fill the gas tank and add a gas treatment stabilizer. A full tank will help cut down on condensation.
  • Change the fuel filter.
  • Change the fluids in the transmission or V-drive.
  • Hook up a garden hose to the water intake hose with a clamp, through the through-hull and turn the water on. Start the engine and run to warm the oil (this makes draining the oil much easier).
  • Turn off engine and drain the oil. There are several kinds of pumps available for this. We’ve used just about everything and discovered a 12-volt pump last season. It’s a bit spendy but makes the process so much easier and cleaner that it’s well worth the money. Be sure to dispose of the used oil correctly.
  • Replace the oil filter.
  • Refill with new oil.

Side note: It’s better to change the engine and transmission oil at your fall lay up because the old oils will most likely contain harmful acids and other contaminants and you don’t want them working on your engine all winter long!

  • Disconnect the positive (+) battery cable.
  • Remove spark plugs. Be careful of any dirt that might fall in to cylinders, it can cause a large repair bill if you get dirt in there!
  • Spray a generous amount of storage fogging oil through the spark plug holes into the cylinder.
  • Crank engine for 1 or 2 seconds to distribute the storage fogging oil.
  • Install new spark plugs. Gap to manufacturers specs.
  • Grease zirk fittings at linkage.

If your boat has a heater (yes many of us water sports lovers have heaters on our boats….it’s cold up here!) or if you have a shower then follow this next section also. Remember we want to also protect from freezing weather, so it’s important to remove any water hiding in the hoses. These next steps will drain/remove the water from engine and lines to the heater and shower.

  • On the exhaust manifold, remove the plugs on each side and let drain.
  • Remove drain on side and temperature sending unit on other side of engine and let drain.
  • Drain water pump impeller housing by loosing screws on housing plate and let drain.
  • Drain heater and shower lines (if you’ve got them) or you can blow out with an air compressor. Find the low points and unhook clamps and drain.

Be sure to leave yourself a note (on the steering wheel near the ignition key?) to remind yourself in the spring of what you need to reconnect and tighten up!

Side note: If your boat has a transmission cooler, it might be helpful to unhook both hoses (in take and out flow) and back flush on the out flow with a garden hose. We (meaning my hubby) have found trash hiding there over the years. This can cause overheating in your transmission.

marine engine fuel filter

marine engine water intake point

marine engine drain

marine engine impeller housing

marine engine temp sending unit marine engine transmission cooler

Not sure what else to do? Read part one and part two of winterizing your boat.

Please remember to help out if you can.

3 Comments posted on "How to winterize your boat, part 3 the inboard gasoline marine engine"
winterize your outboard marine engine on October 13th, 2007 at 7:25 am #

[…] more winterizing your boat in part I of this series or part 2 of this series.    Read More    Comments: 2 Comments posted on “Winter lay […]

Don’t Fall Down On Your Boat’s Fall Lay Up Part 1 on October 13th, 2007 at 7:27 am #

[…] See part three by clicking here.    Read More    Comments: 2 Comments posted on “Don’t Fall Down On Your Boat’s Fall Lay Up Part 1” winterize your outboard marine engine on October 5th, 2007 at 11:14 am # […]

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