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Winterize 2005 Mastercraft X-10 5.7L-MPI Indmar MCX-350 Engine

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  • Winterize 2005 Mastercraft X-10 5.7L-MPI Indmar MCX-350 Engine

    Winterize 2005 Mastercraft X-10 5.7L MPI Indmar MCX 350 Engine

    I'm a first year boat owner, never done any of my own maintenance on any vehicle before. I paid easy 4 figures to shops in this first year of owning so I figured I'd learn to do some stuff on my own (all this was actually pretty easy). After a lot of reading and watching videos I created this for myself but thought I'd share as I'm sure it could be helpful to others. Please let me know if there is anything to correct or if you just see anything in the boat that might need some work! Thanks! PS- I'm doing my best to be overly "keyword" inclusive because the search function on this forum is garbage.

    Pictures included for most, videos linked for some.
    Step 1 (required winterization) – Put Sta-bil 360 Marine Ethanol Treatment & Stabilizer in gas tank, then fill to full with gas (this type of sta-bil says 1 oz per 10 gallons)
    Step 2 (required winterization) – Remove engine panels so you have room to work
    Step 3 (optional maintenance) – Perform oil change (every 50 hours or annually) with cheap pump off amazon (linked)... 5.5 quarts of 15w40 Diesel Engine Oil. Choice Oil Filter: Mobil 1 M1-302a
    Step 4 (optional maintenance) – Perform transmission fluid oil change (every 100 hours or 2 years) with same pump... 4.2 quarts of 15w40 Diesel Engine Oil. Clean/reuse the filter. I have the MC ZF Hurth V-Drive ZF 63IV transmission.
    Step 5 (required winterization) – Drain the block, hoses, strainer, etc. to remove all water from engine. I don't have a heater but if you do see the linked winterization video.
    Step 6 (required winterization) – Remove any ballast bags. Fill hard ballast tanks/pumps/lines with RV Antifreeze... $3 per gallon at Walmart
    Step 7 (optional maintenance) – Replace the raw water pump impeller (every 100 hours or 2 years)... Johnson 09-812B-1 Impeller
    Step 8 (optional maintenance) – Replace the 3 ballast pump impellers (every 100 hours or 2 years)... Jabsco 6303-0107-J Impeller
    Step 9 (required winterization) – Remove the batteries from the boat and store inside until ready to boat
    Step 10 (optional winterization) – Remove spark plugs, spray fogging oil into each cylinder, replace spark plugs. (I opted to skip this... but see winterize mcx and spark plug videos linked below)
    Step 11 (optional winterization) – Run RV Antifreeze into engine in place of water (I opted to skip this... but see winterize mcx video linked below)

    Helpful Links:
    Engine Oil Change Video -
    Trans Fluid Oil Change Video -
    Replace Raw Water Impeller Video -
    Replace Spark Plugs Video -
    Winterize MCX (slightly different engine than mine) -
    2005 MC Owners Manual -
    2005 Indmar Engine Owners Manual -

    Steps 1-9 Supply/Tool List:
    - Stabil 360 Marine Ethanol Treatment and Stabilizer
    - Oil Change Pump Extractor:
    - ¼ in ID x ¼ in FIP hose attachment ($3 at Home Depot)
    - Spare car/marine/rv battery to run extractor pump
    - Oil pan (minimum 2 gallon) or reservoir to hold/recycle old oil
    - Choice Oil Filter: Mobil 1 M1-302a (same size as OEM but longer for more protection)
    - Large ziplock/trash bag for catching old oil filter
    - Phillips and flathead screw drivers
    - Large and small funnels
    - Adjustable wrench
    - 6mm, 8mm, and 1/4 sized allen hex wrenches
    - 10 quarts of 15w40 Diesel Engine Oil (5.5 for engine, 4.2 for transmission)
    - 5/16, 9/16, and 1/2 sized socket wrenches
    - 4 gallons RV Antifreeze (2 for each hard ballast tank)
    - Cheap pour easy system as shown in step 6b picture
    - Johnson 09-812B-1 Impeller (for raw water pump)
    - 3 of Jabsco 6303-0107-J Impeller (for each ballast pump)

    Some Notes:
    - On step 6a you can also just rig something up to shove a smaller hose inside of the vent hole on the side of your boat to get the antifreeze in that way. I had trouble with this because my vent hoses seem to go up (meaning the antifreeze poured right back out at me) before they go down towards the tank. How do you know which one is the vent hose? If you blow into each hole, bilge and emptying lines will be hard (no room to take air), and the vent line will take the air and then blow it back at you almost like a breath.
    - For steps 3, 4, and 7 do watch the videos (I did not make them but they are very helpful and will piece everything together easily)
    - I'd recommend figuring out EXACTLY which engine you have as most people here seem to just say "oh I have the MCX 350" when in reality there are a variety of them (they are very similar but have subtle differences between year, fluid capacities, things of that nature). Go to the linked Indmar Owners Manual and figure out which one you have. My 2005 engine has a plaque on the top that says "MasterCraft Extreme 350 M.P.I. MCX Vortec H.O." and I have a MC ZF Hurth V-Drive ZF 63IV transmission as far as I can tell.
    Last edited by tdp94; 12-13-2021, 04:07 PM.

  • #2
    Continued pictures


    • #3
      More continued pictures


      • #4
        Awesome! I had the MCX in my X30 and loved that thing. Pretty easy to maintain and bulletproof if you take care of it. I always found working on it kind of fun, and hope you find the same!
        '22 XT23 "Big Kahuna"
        '06 X30 (Sold)

        "Sometimes my genius, it's almost frightening" -JC


        • #5
          How did it go for your first time around? That is a very detailed list you've made up!!! Now you know your way around much better and that should make next season much more enjoyable.


          • #6
            I learned a TON about my boat but I certainly ran into a few headaches the first time around. A few of the steps that I documented above were the 2nd or 3rd method I tried after the below stuff failed. 1) The transmission fluid cap where you put the hex key in was stripped, so I had to take a dremel to the nut head and turn it into something I could just slip an adjustable wrench on to. 2) My engine didn't exactly look like the other MCX 350's I was watching videos on for draining the block, took some guess and check. 3) My T-hookup garden hose fitting on the ballast manifold I couldn't get working so abandoned that. I had the wrong hole for the ballast vent, then when I had the right hole I ran into an angle/gravity issue. 4) The impeller housing is blocked by the exhaust silencer so that wasn't as straightforward as expected but removing the whole pump worked just fine.

            Next year will be a breeeeeeze! Took me the entire weekend of Friday night, Saturday, Sunday to get through everything. Next year I anticipate with my little guide here, ~3 hours and done.


            • #7
              Ouch, that is usually the best way to learn although not the most pleasant! Keep up the good work!


              • #8
                Thanks for linking my winterization video. I also have one for changing transmission fluid.
                We defy the mafia!