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Heater Core replacement for 3 vent - 2003 Malibu

hemlockhemlock Posts: 146 Baller
My heater core finally bit the bullet and leaks.
Yanked it out, and now looking online, it appears heatercraft makes a new core (for 3 vent - 300h) and it requires a new box and blower. Anyone know if there is an automotive equivalent? or do you think some dealers still may carry the old style?
Here's a pic, from bakesonline, I have the older one.
I'm really hoping I don't have to buy a whole new system.


  • eyepeelereyepeeler Posts: 169 Baller
    To me, the heater is an important part of your boat, especially if you ski year-round. My wife used to like the heater even on July evenings in Tennessee. I would update to the new core, box and blower if you can't find an old style core anywhere. October will be here before you know it.
    Matt Dillon
  • dvskierdvskier Posts: 498 Crazy Baller
    I used a local radiator shop, simply took the old heater core to them and they matched it to a new one. Works great, cost $50.
  • UWSkierUWSkier Posts: 1,175 Mega Baller
    Seem to recall there's a Napa model that fits. Does Heatercraft not sell just the core anymore? I've replaced a few cores in the past and never needed entire new box.
  • RednucleusRednucleus Posts: 257 Baller
    Last time I did it I took it to a local radiator shop. They can repair or replace it
  • MISkierMISkier Posts: 2,547 Mega Baller
    @UWSkier, HeaterCraft redesigned their core a while back. Older models cannot take the new replacement core. That is why they are recommending a new box and blower. I just replaced mine this year, but I was lucky enough to have the new design and just needed the core.
    The worst slalom equipment I own is between my ears.
  • DekeDeke Posts: 380 Baller
    My 99 RLX went through several cores in it's first few years which were replaced by HC. The last one was the whole new box and all due to the new design, which was to supposed to correct those issues. It worked! Haven't had one go bad since.
  • BongoBongo Posts: 33 Baller
    Common replacements were the heater cores from mid-1970's Ford vehicles; F-100, Vans or maybe a Thunderbird. NAPA 660-3100 is one that looks closest; $30.

    I know in my case when I did this a few years ago, I had to slightly trim the tin on the box where the inlet goes.
  • skimtbskimtb Posts: 260 Baller
    I thought I heard that they used to use normal automotive cores (like the old ford one above), but switched to stainless or something non corrosive so it lasts longer. Maybe that’s the “new” one.
  • hemlockhemlock Posts: 146 Baller
    Thanks, I have a local rad shop near my place. I will try that and see if they can either repair it or fabricate one for me.
  • dvskierdvskier Posts: 498 Crazy Baller
    My shop has been able to locate a new replacement each time I have used them. I've had 2 replacements in the past 10 years. They said it was likely due to the jarring of the tubes incurred from the wakes. Our lake water is pure and clean so that made sense to me.
  • hemlockhemlock Posts: 146 Baller
    After talking to some rad shops, it was too expensive to fix.
    So, I ended buying a whole new heater system from heater craft. (3 vent, via my dealer)

    Good news, this new system came with the Y adapter to fix the low heat at idle.
    I never had the Y adapter, (just two hoses from block to the heater core and for years have always had cold air on idle)
    So, I'm excited to fix my heater, and fix the low heat at idle.

    Attached is the pic of my Y adapter. From what I've read online, is that it's best to put the Y adapter in "front" of the impeller. But, apparently Malibu puts the Y adapter "after" the impeller. Now looking at this particular Y adapter, I'm pretty sure it's not the correct size to fit on the "front" of the impeller or raw water intake hose. (Perhaps my older boat has a larger raw water intake hose?) It looks way too small.
    I don't have a recent photo of my raw water intake hose (the heavy stiff one) but I believe its too big to fit this Y adapter. And, I do kinda recall that the impeller connection is smaller "after" the impeller that feeds into the transmission cooler. And this Y adapter looks like it would fit on that section of hose.
    So, for those of you that have modern Malibu boats or other boats with a Y adapter "after" the impeller, do you have heat a low idle?
    Thanks in advance for advice.

  • MISkierMISkier Posts: 2,547 Mega Baller
    I have a 2009 Response LX. I installed the Y adapter before the raw water pump in the section of hose leading from the hull intake to the pump.
    The worst slalom equipment I own is between my ears.
  • jhughesjhughes Posts: 934 Mega Baller
    The Y adapter goes before the RW pump and they make it in various sizes. The idea is it draws the water through the core using the suction of the RW pump. You'll notice inside the smaller part of the Y the flow is blocked to about 1/8" hole in there.

    I know I've put the new style in my old housing successfully on the 2000 SN but it may have required a little cutting of the box here and there, nothing serious as I recall. FWIW before that I did the Napa equivalent and that didn't last long in there and didn't fit exactly either. The current HC core is tubular and should last a long time.
  • UWSkierUWSkier Posts: 1,175 Mega Baller
    Malibu does install these after the RW pump from the factory but this is somewhat pointless and doesn't really work well in that location. You want it before the RW pump to allow the pump to pull water through the system.

    Or you can dump the Y adapter and spend $20 dollars on a small electric pump like I did on mine. Heat at idle, yeah, that's cool. I get heat with the engine off now. That's a neat trick.
  • hemlockhemlock Posts: 146 Baller
    Thanks @UWSkier @jhughes @MISkier

    You would think that water passing through the impeller going into the transmission cooler would still provide enough venturi effect to pull water away from the core, thus hot water into the core.
    But if it doesn't which seems to be the consensus, do you think it's safe to put a reducer in my raw water intake so the Y adapter would fit?
    In other words, add a reducer to my intake hose down to 1-1/8 inch, attach y adapter, then add enlarger fitting back to the 2 inch hose which then attaches to the impeller.
  • jhughesjhughes Posts: 934 Mega Baller
    So it's 2" hose all the way to the RW intake? I don't think I've ever seen that on a ski boat.
  • hemlockhemlock Posts: 146 Baller
    edited August 2
    Yes sorry, not really sure on the size of the intake hose. :blush:
    But I sense the intake hose connection is bigger than the connection after the impeller.
    Hoping to get out to the lake tomorrow to confirm sizes.
  • hemlockhemlock Posts: 146 Baller
    Okay, I was totally wrong about the impeller hose sizes. They look to be exactly the same. So this is good news, since now I know the Y-adapter will fit on either side, and thus I can install it onto the raw water intake. :smiley:
    Now I'm not sure which hose is the return from the heater core.
    Is the return the one that goes to the circulation pump area? or the one to the top of the block?

    The impeller.

    Lower heater core hose.

    Upper heater core hose.

  • MISkierMISkier Posts: 2,547 Mega Baller
    @hemlock, when I did mine, I had a connection to the top of the block and the other connection was to the Y-pipe that was installed between the hull intake and the raw water pump. I did not have any connection to the circulation pump. So, you would need to install/re-install the plug on that pump where the hose now connects.
    The worst slalom equipment I own is between my ears.
  • hemlockhemlock Posts: 146 Baller
    Thanks @MISkier.
    That sounds about right, that the top block hose "feeds" the heater core, and the return goes to the Y adapter. I guess with my original old setup, the lower circulation pump hose actually pulled water. So, I will plug the lower one.
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