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  1. #1

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    Msx 150 open loop water cooling

    I'm rebulding my msx and now I'm thinking how to solve the problem with water pump intermediate plastic gear. My isn't broken but I don't want wait for this.

    The water cooling system on 110/150 isn't 100% closed loop system, in fact only cylinder and turbo core-assy are cooled with the closed loop and everything else with fresh/salt water. We also know that Hydrospace s4 use a open loop system.

    My question is, can I remove the mechanical waper pump and use only the flow generated by jet pump?


  2. #2
    ripcuda's Avatar
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    No. Even the Hydrospace Weber engine uses the water pump in it's open-loop cooling system. Water pressure from the jet-pump alone is not fully sufficient for proper cooling needs at all times. Imagine full boosting around (lots of water pressure)... then coming to an idle (much less water pressure).

    On the MSX Weber, the engine, turbo, oil cooler and heat exchanger are the closed-loop (coolant) system. The intercooler, heat exchanger, oil tank and exhaust manifold (plus exhaust water injection) are the open-loop (freshwater) system.

    Cheers!

  3. #3

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    Ok, but what about the heat exchanger? Without fresh water it can't cool refrigerant in closed loop.

    And why 2t engines haven't the same overheating problem? They haven't a second water pump like Weber.
    Last edited by Tony2k; 05-27-2015 at 11:18 AM.

  4. #4
    ripcuda's Avatar
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    Could an engine the size of the Weber be completely open-looped cooled without a waterpump? Sure, if it was designed that way. But the Weber was designed to use a waterpump even in the open-loop cooling system setup and as such you can't just not use the waterpump and expect it all to work fine... without serious custom plumbing and a lot of experimenting.

    Freshwater flow doesn't stop at idle... it's just at a much lesser pressure(flow) than at WOT. Plus having a closed-loop coolant system gives the engine a large capacity of fluid to put its heat into... which then transfers it to the cooler freshwater circuit via the heat exchanger. Plus the heat exchanger is only 2nd in line to the intercooler for receiving fresh water off the pump... so even at reduced idle pressures, it's still efficient enough to do what needs to be done. This was all researched and designed by much smarter folks than me... who engineered the Weber. They would have figured out all those variables... flow, restrictions, sizing, efficiencies... across varying temperatures of air and water. I'm still amazed it all works as well as it does, stuffed into such a small space in a jetski hull.

    Cheers!

  5. #5

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    Ok, condidering that I use my ski 90% of the time on fresh water do you think that is a good choice go with open loop or is always better closed loop?

  6. #6
    hill160881's Avatar
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    Just keep it closed loop.

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  8. #7
    ripcuda's Avatar
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    Agreed. The stock cooling system works fine.
    It does have that plastic waterpump drive gear I understand your concerned about... but only way to change that is a full rebuild with FST metal parts.

    Cheers!

  9. #8

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    Or another solution is replace the mechanical pump with a Bosch brushless pump like this:




  10. #9
    ripcuda's Avatar
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    Seems like a whole lot of effort. You would need a custom bracket to hold it. A way to power it. And a bunch of custom plumbing connections mate it up.

    If your rebuilding your MSX currently... why not just buy the FST metal parts and fix it for good... like factory?

    Cheers!

  11. #10
    hill160881's Avatar
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    First off the pressure spikes from the pump may dammage that pump, they were not designed for head pressures like the jet pump will provide. They were designed for vacuum in and pressure out. That pump is way to small. The other issue is you will need a thermal grounding switch to turn it on at temp or a relay to a power source to turn it on when the ski is running. Either way I would not trust an expensive difficult engine like this to a small cheap elecrronic pump. The pump I used on my race car was $300 and I still would not trust it to not blow a seal from the head pressure.

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