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DIY Winterization of a 1971 Mercruiser 165 sterndrive.

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  • DIY Winterization of a 1971 Mercruiser 165 sterndrive.

    The past 2 years I have had my boat winterized at the same shop. They charge $200 for the service. After talking to them about their winterizing process, all they do is fog the motor when it's up to temp and remove the plugs and hoses from the block to let any water drain. They do NOT use antifreeze, and they obviously recommend leaving the plugs and hoses disconnected until spring. But that's it. I live in Tennessee, I do not leave the boat in the water, and it stays covered when out of season. I can't justify spending $200 for that service when it's something I could easily do myself. The past 2 years I haven't had any trouble getting the boat back in the water in the spring.

    My question is: Are there any other precautions I should take if I'm thinking about winterizing myself this year? I've heard of people using compressed air to blow through the motor and try to blow as much water out as possible, but I have never done that before. Any info or tips from previous experience will help!


  • #2
    If its a straight inline 6 cylinder that your talking about all I would do is remove the bronze plugs located generally just above the oil pan in the center of the engine, I believe there is one on each side. Then remove the bronze plug on the bottom of the exhaust manifold and the one on the side of the exhaust riser. They have the square heads on them . They do make square pipe plug sockets but a open end wrench will work. If you want you can blow air into the openings of where the plugs were. Make sure there is no sediment in the holes that wont allow the water to run out,stick a wire in them to make sure.To me fogging is ok but I don't do it as the boat is only sitting for 5-6 months and I have had cars that sat longer without issues when I fire them up .Never bothered removing hoses,if it makes you feel better you can always loosen the bottom clamps on them where water may accumulate.
    Cool Runnings,,, Mr.88


    • #3
      Here's what a marina told me when I made a frantic call due to a freak October storm years back...

      Pull the drain plugs in the block and exhaust risers.
      Pull the hoses off the water pump.

      As long as temps weren't below 30 for a while, I want to say 3 days, you're fine. All they ever did in winterizing the boat was the above and then bagged the parts & clamps in a zippy bag and tied it to my steering wheel for spring time. I don't believe they ever fogged it - MPI V8. Darn sure they didn't run antifreeze through it - would have drained out with all the plugs and hoses disconnected I do know they put gas treatment in the tank.

      I did that (2) years straight on my own with no issues - oil still looked like honey when I checked. And yes that was to save around $200 for the winterization, same as you. This is from a guy in NY who sees a lot of snow, ice, whatnot...

      Disclaimer: I paid to have mine winterized this year by a marina as my motor is under a factory warranty.
      2017 Chaparral 19 H2O Ski & Fish w./4.3L 180HP Merc Alpha
      2005 Four Winns 200Le x/5.0L Volvo SX-M (270HP - FI) - ordered new, traded in on Chaparral
      1999 Bayliner Capri 1800LS w/2000 Honda 115HP - ordered new, traded in on Four Winns
      1956 MFG 15' w/matching Evinrude Big Twin 30HP - presumed to be a sandbox somewhere

      Tow Vehicle:
      2017 Toyota 4Runner SR5 Premium 4x4


      • #4
        Definitely make sure to poke something--wire, pick--something into each plug hole. There can be flakes of sediment or rust that blocks the hole and keeps water from draining.
        You really should also change the gear lube when you winterize, more so in the great north where it gets really cold, but you don't wanna risk have some water in the gear lube that could freeze up. Plus, changing gear lube should be done seasonally, and doing it in the fall makes one less thing to address in the spring!


        • #5
          start motor on muffs.....run to warm
          change oil
          change gear oil
          start motor to get oil circulating
          shut off motor
          pull drain plugs on block and manifold(s)
          prod drains
          pull large hose on water pump and empty
          lower drive
          pull prop, grease splines

          or simply pull drive and store indoors

          boat is now winterized

          put plugs in and pour marine PG anti-freeze into hoses with funnel if it makes you warm and fuzzy (not needed, however many people do)

          that will be $200
          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

          Past Boats
          1970 Wooster Hellion - Merc 9.8
          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

          What’s behind you doesn’t matter.Enzo Ferrari


          • #6
            You can use compressed air, or a wet/dry vacuum, to help get rid of water in lines and engine. You can also just tow the boat around a few corners and up and down some hills to slosh out any water after it has drained. No need for antifreeze, and after you are confident that the system is drained it is just fine to reinstall plugs and reconnect all lines.

            Putting fresh oil in and running the engine takes any acids that build up in used oil away from the bearings and helps their life.


            • #7
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              That part that suggests changing the oil in the lower unit is often overlooked. It's REALLY important! If your lower unit has developed a leak during this past boating season, that lower unit could easily contain enough water to cause freeze damage. If there isn't enough water to cause freeze damage, there could still be enough to cause bearings to rust.

              It's easy to check for water, even if you don't change the fluid. You just pull the bottom plug for just a second. If you see water, there's an issue. Oil floats on water, letting the water settle to the bottom if the boat is just sitting. If you see no water when the plug is removed, you're good to go! The drop or 2 you lost checking won't hurt a thing.