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Monsoon 335 winterization with heater

SkiphreakSkiphreak Posts: 9 New Baller
In the middle of winterizing 2003 Malibu RLXI monsoon 335 - boat is equipped w a heater. Do I need to drain the hoses that run to the heater core from the block? Or would have all that water already drained out through the block drain plugs or the J hose? Thanks!


  • RednucleusRednucleus Posts: 554 Crazy Baller
    I put an antifreeze flush T in the low point of a hose so I can drain it with a shop vac to prevent freezing.
  • SkiphreakSkiphreak Posts: 9 New Baller
    I should have also noted that the hoses are not connected to a heater core (the core cracked from age and I haven’t replaced). The hoses are just connected by a plastic connecter piece.
  • Mick04Mick04 Posts: 62 Baller
    They probably still have water in them. Take the 5 minutes to disconnect both ends and blow through one end to clear it. If there was no water in it, you will know for the future. Better than wondering all winter if you stored you boat correctly.
  • 6balls6balls Posts: 5,556 Mega Baller
    IF you run antifreeze thru your hot block will it not also circulate thru the heater core?
    Dave Ross--die cancer die
  • Mick04Mick04 Posts: 62 Baller
    6balls, that is exactly what I tried this year. Running antifreeze through engine with heater running on hi. When I pulled the heater hoses to check, it was clear water, nothing made it to the core. The rest of engine had antifreeze (block, J pipes, risers). I’m guessing my engine running at idle doesn’t provide enough water pressure to push all the way up to heater core. Explains why heater blows cold after a couple minutes, sitting at end of course swapping skiers.
  • UWSkierUWSkier Posts: 1,620 Mega Baller
    @Mick04 correct. You need to have the engine running at higher RPM to cycle through the core unless you have the "y pipe" mod or the aux pump mod.
    @Skiphreak if you don't have a core inline, I wouldn't worry about it.
    boats are like girlfriends you love them however there is another one around the corner - bananaron, July 21, 2020
  • 6balls6balls Posts: 5,556 Mega Baller
    Interesting thanks. Would it be enough to rev it when slurping up the anti-freeze? I've already winterized and didn't do that, so hopefully my core will make it. I did freeze/crack one some years ago on a freezing temp night in the spring after we had already had the boat in the water.
    Dave Ross--die cancer die
  • oldjeepoldjeep Posts: 3,753 ★★★Triple Panda Award Recipient ★★★
    Even if you already winterized it. Just open up the engine cover, remove the 2 heater hoses from the block and blow them out. Then just pour antifreeze into the top hose and you are good to go
    Chuck P
    Not a mechanic but I play one at home
  • SkiphreakSkiphreak Posts: 9 New Baller
    Thanks everybody for the tips. Just curious (and a bit off topic) do you guys run antifreeze or just go dry? This is my first winter w this boat (never winterized an inboard previously) and have seen people go both ways. I was planning on not using antifreeze.
  • MISkierMISkier Posts: 3,120 Mega Baller
    Put antifreeze in it to keep corrosion at bay.
    The worst slalom equipment I own is between my ears.
  • oldjeepoldjeep Posts: 3,753 ★★★Triple Panda Award Recipient ★★★
    edited October 2020
    I use antifreeze - poured into the heater circuit and the block after all the water has been drained.
    I use it for corrosion protection mainly, not to compensate for a bad draining process.

    On the standard 5.7 with crank mounted raw water pump,
    1) I disconnect my manifold crossover hose in the middle (older boats have a drain on each manifold).
    2) I remove the knock sensors and plugs from both sides of the block. (older boats have one knock sensor and just a plug on the other side
    3) I remove the J hose
    4) I remove the hose between the raw water pump and trans cooler
    5) I remove both hoses for the heater off the block and then blow the water out - blow from one side and then once you get air blow from the other side if you don't know the orientation of the core.
    6) I don't remove the plugs from my V-drive, but that is because it self drains in my boat (doesn't in all boats)

    Once that is all done I reinstall everything from steps 1 & 2. Put the lower part of the J hose on and leave the top free
    Reinstall the pump to trans cooler hose.
    Reinstall the lower heater hose onto the circulating pump
    Pour -50 marine antifreeze into the upper heater hose using a funnel and keep filling until I hear it flow into the circulating pump.
    Reinstall the upper heater hose at the top of block
    Use a funnel and pour whatever is left of 2 gallons of antifreeze in through the upper part of the J hose
    Hook the top of the J hose back up.

    Whole process takes maybe 45 minutes on my v-drive. Would be faster on an inboard because things are easier to get at.
    Chuck P
    Not a mechanic but I play one at home
  • davemacdavemac Posts: 456 Baller
    I have same boat (03 RLXI 750hrs). I drain it all down and go dry with winterization.
    I still have the original heater core, although the mux switch is failing (if anyone should have one, PM me). Disconnect both heater hoses from block, and blow into top hose, water comes out the bottom one. You can blow it out by mouth, or some quick, short bursts with a compressor. I then use a funnel, pour some RV antifreeze into top hose, and blow it through til pink stuff running out bottom hose. I re-attach (all) the hoses in the Spring.
  • DWDW Posts: 2,296 Mega Baller
    Do not assume antifreeze will pass through the heater core doing a winterization on the driveway unless you actually have a separate pump that forces the fluid through it. Your heater core may or may not have more flow resistance than where it T's off on the inlet side than the other side of the T. Many circuits take water off the exhaust manifold line and if not pumping a fair amount of water, the heater core won't see much if any flow. Also note, it is the most fragile component in the system so makes sense to guarantee it has antifreeze in it or is empty. Also, don't force air at high pressure (from a compressor) though the core as that can easily ruin it.
  • DekeDeke Posts: 398 Baller
    My 99 RLX has both a heater and a shower. I installed quick connect fittings on all of the heater and shower hoses so that it can be reconfigured to use the shower pump to pump antifreeze through both the shower and heater at the same time. When I see pink coming out, both are full and the hoses can be returned to the original setup.
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