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  1. #1

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    EMM Cooling on the msx 140

    Hello everyone I have an msx 140 and have a couple cooling related questions!

    -on the '04 msx 140, is there a specific reason why the EMM is cooled with "moderate to high" temperature water from the stator/flywheel instead of having its own small tee off of the main 3/4" inlet hose off the back of the ski?

    -would there be an adverse affect to the EMM if the cooling hose to it was rerouted/re-tee'd to come directly off of the "cold/fresh" water supply instead of thru the engine? (assuming you also replumbed the existing engine cooling hose back to the existing outlet).

    -Is the cooling water flow into the ski "powered" by the water off of the jet pump? or is there another water pump somewhere in the ski that is drawing the water from the pump housing (not likely, but I wasn't sure)

    Thanks!


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    The only water pump is a 2-stroke Polaris watercraft is the main pump that provides forward motion.

    There is a pressurized water take-off on the right side of the pump nozzle (not the steering nozzle) which feeds a platic or metal tube that runs forward into the hull.

    Have you measured the water temperatures going into your EMM?

  3. #3

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    Thank you for your reply! I have not measured the cooling water intake temperatures to the EMM, however looking at the cooling water diagrams, it just didn't seem to make sense to me why the EMM would be cooled by water that has already picked up heat from the engine. I saw your thread on the 'pisser' installation for verifying EMM cooling water flow and I believe you had mentioned that the exit water temperatures get pretty hot, especially at higher engine RPMs and it seems to be due to the fact that EMM cooling water is being preheated by the engine.

    I wanted to check with some of the knowledgeable people on here to see if I correctly understood how the cooling system worked.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Makon View Post
    Thank you for your reply! I have not measured the cooling water intake temperatures to the EMM, however looking at the cooling water diagrams, it just didn't seem to make sense to me why the EMM would be cooled by water that has already picked up heat from the engine.

    I saw your thread on the 'pisser' installation for verifying EMM cooling water flow and I believe you had mentioned that the exit water temperatures get pretty hot, especially at higher engine RPMs and it seems to be due to the fact that EMM cooling water is being preheated by the engine.

    I wanted to check with some of the knowledgeable people on here to see if I correctly understood how the cooling system worked.
    I have not reread that old post before replying here, but I don't recall having any concern at the water temperature rise exiting from the EMM pisser.

    I expect the EMM can tolerate quite warm water temperatures as might be expected in tropical waters, plus some heat rise from the engine stator and EMM itself. For the waters I normally ride in the intake water is typically fairly cool even in summer, so I never considered adding yet another water feed just for the EMM.

    My own machines also experience below freezing winter storage temperatures so I would need to plan any modification for sufficient drainage during winterization. EMM cooling water source was just not something I have wanted to modify.

    What the EMM does not tolerate is no water cooling at all! As long as the water flow is sufficient I would expect the EMM to be reasonably happy, temperature wise, with stock water cooling.

    If you did provide a more direct and presumably cooler water flow through the EMM I don't see any huge downside, other than potential water drainage complications prior to winter storage.

    It is possible that the EMM monitors the temperature of the water coming into the EMM as a proxy for the temperature of the water cooling the actual engine. I do not have any direct evidence for this at hand, and of course there is a separate direct temp sensor on the exhaust system so I could be entirely wrong on what the EMM does with the water temp coming in.

  5. #5

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    Right, I am sure it can tolerate elevated water temps and I operate the ski in 'moderately' warm water in the summer. I haven't had any temperature related issues (never been into SLOW mode) and I know electronics can handle pretty high temperatures (close to 180deg F. +) prior to burning up so with that in mind you could still cool the EMM even with 100-110 deg. 'warm' water off the stator.

    My main reason of considering replumbing the EMM was because I have been thinking about ways to reduce the IAT's to the engine, in the form of doing a DIY fabricated intake housing with a water cooled coil (similar to a turbo - intercooler, but without the turbo). While considering where to tap the coil water into the existing circulation system, I saw how the EMM was plumbed and got curious lol.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Makon View Post
    ... I have been thinking about ways to reduce the IAT's to the engine, in the form of doing a DIY fabricated intake housing with a water cooled coil (similar to a turbo - intercooler, but without the turbo). While considering where to tap the coil water into the existing circulation system, I saw how the EMM was plumbed and got curious ...
    An air intercooler without a super/turbo charger may introduce air flow restrictions that could counter the hoped for gains.

    You may find the easiest and somewhat effective power upgrade to come from adding another cold air intake and directing the outside air flow very close to the flame arrestor.

    I can tell you that on a stock Virage TXi the two stock outside air intakes (a pair of 2.x inch flex hoses and hull fittings) are not enough. When I blip the throttle on the Virage TXi while it is sitting on the trailer you can see the seat actually get sucked downwards. That means air pressure reduction inside the hull, which means outside air cannot get into the hull fast enough.

    If you do modify the air intakes, keep in mind that when the hull is floating upside down in the water (which can happen) you don't want the air intakes to allow rapid water flooding into the inverted hull. This is why the stock air flex tube open ends are positioned very low in the hull. If the hull is accidentally inverted those air tube ends would then be above the outside water surface level, thereby limiting the rate that water seeps into the hull.

    And of course you do not want splashed water (aggressive riding) to get directed into the engine's air intake. Water ingestion into the engine can cause severe damage.

  7. #7

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    Yeah those are all certainly factors for consideration. I do ride fairly aggressively and in lots of chop/waves so water intrusion is definitely a concern with more hull openings (I have submarined the ski through large waves before, which was pretty awesome!), fortunately I have never capsized it. The one time I got close to doing that I was able to push the ski the other direction while I flew off the side of it haha.

    With the intercooler idea I was going to make it fairly larger surface area (much larger than the free area under the flame arrestor cover) so as to keep air velocities relatively low. I was thinking of using a 12" x 5" copper coil which would be completely open on one side.

    Do you happen to know what the intake manifold is able to flow in terms of air quantity (CFM)? Then I can try and match up the free areas. I'll try and whip up a sketch of what am envisioning this to look like and put it in another thread if I decide to do it.

    Thank you for the info man, its much appreciated.

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