Filed Under (Boat/Trailer Maintenance) by Debbie on 03-11-2007

Being able to winterize your marine diesel engine is a valuable skill to have if you live in a cold climate area.  We winterize our engine just in case we get an artic blast during winter.  It doesn’t take long and we figure in the end it’s cheaper than the damage should we have that artic air come through.  So, here’s our list:

  • Change the engine oil, oil filter and transmission oil at the end of fall or beginning of winter. Run the engine a few minutes to heat the oil, it will help with the pump out. 

oil pump

removing oil filter 

The old oil will contain a bunch of contaminants and harmful acids by the end of the season.  You don’t want to let it sit there all winter working on your engine and transmission.  If you have a freshwater cooled engine, change the antifreeze.  I understand the antifreeze doesn’t wear out but it has several kinds of corrosion fighting additives that do.

Where to find impeller pump on Universal Diesel

  • Drain the raw water system being sure to check and drain any low spots.  Remove the flexable impeller and lightly grease with vaseline (you know, the stuff for baby butts) and then replace it.  You can also leave the pump cover loose so it doesn’t stick to it.  Run the engine for a second to expell any water that’s hiding.
  • Or (this is what we do) you close off the seacock and using a T’ed off the hoseWinterize marine diesel engine 1

you can pump the pink anitfreeze (nontoxic) through the engine, have someone at the back to catch it in a bucket so it doesn’t go in the water and then shut off the engine as soon as it starts to pump out the back.  End of hose and bucket

  • Check the primary fuel filter for water and debris and clean if needed.  Change the secondary fuel filter and then fill your fuel tank (helps cut down on condensation) and add a fuel treatment. 

 Fuel line first bleed

 Be sure to bleed your your fuel line to remove any air caused by changing your fuel filter.  Turn the ignition key to pump the fuel through the lines but don’t try to turn over the engine.  Have a rag handy to catch the fuel.

second fuel line bleed

  • Spritz a small amount of oil into the air inlet manifold if you can and turn over the engine (don’t start it!) this will pull the oil into the cylinders and smear it around the walls.
  • Grease all your grease points.
  • Seal off all openings into the engine.  Put a note somewhere you won’t miss and remind yourself of each spot you need to open next year before you start the engine!
  • This is also a good time to check your hoses for any cracking, bulging or softening. Pay particular attention to hoses on the hot side of the cooling and exhaust system.
  • Check your propeller shaft set screws or through bolt.
  • Tighten the stuffing box nut to stop any drips.  Add this to your note so you loosen it next year or you’ll over heat your shaft!
  • This is also a good time to check your sacrificial anodes.  We were suprised when we discovered one in the engine cooling system.  It was almost gone when we found it.  Glad my hubby was lesiurly perusing the owners manual.

Of course, the last thought here has to be this.  Once you winterize your engine Neptune will chuckle because Murphy’s Law prevails!  You’ll get a day of really nice weather….  Oh well, sit in the cockpit and have a nice lunch. As always, if something doesn’t make sense check with your local diesel mechanic. If you found this helpful please click on the help out button below, thanks!

Find more articles about winterizing your boat ‘here’.

2 Comments posted on "How to winterize a marine diesel engine"
Kevin Walters on November 6th, 2007 at 11:46 am #

Good looking website, Debbie! There’s a lot of great infomartion here. Makes me wish I could trailer my boat to the Pacific Northwest to do some boating. Thanks for checking out my site (!

Nike Pas Cher on July 29th, 2016 at 1:23 am #

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