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  1. #1

    Removed my Thermostat today and this is what I observed

    So we took the SL 750 out today (the SLX is waiting on parts) and ran it for about an hour and I did my routine check and found that the heads were too hot to touch. I mean really hot. I remember reading that you should be able to hold you hand on the engine without it burning. So I broke out the tools and took out the thermostat. WOW! Believe it of not the ski ran better. Alot better. I do not know why I did not do this sooner. Now our water here i Texas is REALLY warm so I think I can get away with it. Got back to the shore and the heads and jugs were just warm. Big improvement.

    Also before the MFD said 44 MPH and after I took it out I hit 50. Now I know that is not accurate, but that is a big jump. I guess the engine just likes to run cooler.

  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    These 2-stroke engines like to run right around 143F, which is where the thermostat will try to keep the temperature, if it is working properly.

    You can test that thermostat in a pot of warm water on the stove. Put a thermometer in the pot, and watch the thermostat as the water temp climbs. Right around 140-150F on the thermometer, you should see the thermostat visibly open up.

    However, when running at high speed, the important part is not the thermostat. It is the pressure by-pass valve. That is the long spring with a plastic tip that sits beside the thermostat.

    At higher engine RPM, the extra water pressure from the jet pump through the cooling system is supposed to force the by-pass plunger down, and allow extra water flow.

    If that by-pass has become damaged or stuck in place, it will cause the engine to overheat, even if the thermostat is working.

    All that said, I am sure you will be fine running without the thermostat. In fact, you may want to remove the by-pass valve too. That will maximize water flow through your engine, which in warm water is just fine.

    The thermostat and pressure by-pass are more important when riding in cold and cool water, where over-cooling the engine is a real possibility.

  3. #3
    retro's Avatar
    Join Date
    Jun 2009
    Sounds like it's running better and cooler. Thats a plus for any carbed motor.

  4. #4
    I removed both the t-stat and the pop off. I also tested my t-stat on the stove, and it did open. The light never lit on the MFD for heat, but when I put my hand on the head it burned me. If i get on of those IR heat reader guns what should my readings be on the head?

  5. #5
    You should be reading around 140ºF on the heads. Mine usually run about 135-145.

  6. #6
    bowsniper's Avatar
    Join Date
    Aug 2008
    The pipe should be in the 90's the heads about 130-143 and anywhere else around 103-140. I use a infrared reader and those are the reading I get on my slt..

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