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  1. #1
    scorp's Avatar
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    Thermostat & pop off valve question

    So im doing a rebuild on a 1200 carbed engine, during reassembly I was about to re-install
    the water rail and decided what the heck let me take It apart and check the pop-off & therm.
    Well surprise.........both missing. previous owner obviously removed them?? Why?
    overheating maybe? any pros to not having them in?
    My question is how bad is/was this for the engine. BTW Engine crank bearings failed.

    Thanks
    steve


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What model and year was this engine form/for?

    BTW, for others who may read this later, it is ALWAYS a good idea to open the thermostat housing and inspect inside.The pressure release valve plastic tip can wear and stick or jam when worn.

    The thermostat itself can clog with debris or have failed. It can be tested in a pot of warm water. Watch the temperature as the water is heated to check that it opens at the expected 143F or close to that.

  3. #3
    john zigler's Avatar
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    I always take them out....

    Well actually, I "gut" the thermostat, and re-install the empty housing.

    Going by memory (which is NOT all that good anymore) I think some of the later Polaris machines did not have thermostats. The housings were empty.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by john zigler View Post
    ... I think some of the later Polaris machines did not have thermostats. The housings were empty.
    There seems to be lots of detail difference across the models and years, regarding the cooling system. The water bar manifold openings to different cylinders are not the same in all model years, for example.

    Even though Polaris factory did delete the stock thermostat from certain models/years does not mean that is the necessarily best choice for other models, or for other use cases.

    Over cooling of these engines seems common among owners who have changed the cooling system. I don't know why so many people seem to think that engine cooling is a problem on the Polaris watercraft. There are cooling tweaks that can provide benefits if the person knows why they are making the changes, but for mostly stock machines the stock thermostat configuration seems to work well.

    When ByranP installed his water temp gauge on his X45 (I think it was the X45 with 1200 engine) he noticed that the engine water exit temp goes DOWN as the engine RPM rises, with the thermostat in place. At idle, the thermostat helps maintain a reasonable minimum engine temperature.

  5. #5
    ripcuda's Avatar
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    '00/'01(?) Virage TX 1200's had no t-stat in them. My Rio ('00 Virage TX engine) had none. I got a water-rail with t-stat and installed it on mine to bump up cylinder temps since I run in cooler waters.

    Cheers!

  6. #6
    scorp's Avatar
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    I got the engine years ago as part of a deal when I bought a ski, don't remember what it was in,
    when my 900 engine blew I dropped this 1200 in and it ran for 4 seasons till last year.
    so it's possible it didn't have either of them in to begin with, I like the idea of no thermostat,
    what about the pop off? should I leave that out too?

  7. #7
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    I think the 2000s had no thermostat/popoff. They went back to them for 2001.

    I personally prefer to keep and maintain them. I could see over cooling being a problem if you run in cold water.

    I do have a gauge on my X45. I also have one on my Matrix. The matrix has no thermostat/popoff. The Matrix temp gauge rarely moves, unless I am in water that is over 70 degrees. Then the temp only rises after coming back to idle after a high speed run.

    The gauge on my X45 shows exactly how the system is designed. At idle, the temp will climb to 140F degrees or a little more. It will then hold steady at 140. As soon as you increase speed enough to open the popoff, then the water temp falls back to around 100 degrees. Running in cold water (colder than about 50 degrees), the temp drops all the way down to 60F on the gauge and sometimes lower than that if the water is really cold.

    The thermostat/popoff assembly is designed to keep some heat in the motor. If you run warmer waters, removing it should probably be ok. You may need to adjust the carbs on the bottom end to deal with the cooler engine temps.

    One more thing to keep in mind that I have observed. Without a thermostat/popoff, at low speed it will affect the water flow to the exhaust stinger water injection on the exhaust pipe. The stinger water feed needs the water pressure that is built up in the cooling system with the thermostat/popoff in place to feed the stinger water. Without that pressure built up in the cooling system, it changes water flow to the pipe. This was all designed together by the Polaris engineers.

    I know other watercraft brands did not use a thermostat at all. However, their cooling systems were most likely designed with this in mind. Flow through the system is probably less in other brands to keep a little heat in the motor.

    I run in a wide variety of water temps. Anywhere from 32 to 85 degree water temps. I choose to keep the thermostat/popoff for the purpose of keeping engine temps roughly the same no matter the water temp.

    One more thing to keep in mind. Removing the thermostat/popoff in a FICHT motor is not an option. They must remain in place. The regulated engine temp is important to the system as a whole.

  8. #8
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    With the self drain from the exhaust manifold as the factory had it configured the pto gets way cool. water bypasses the exhaust altogether and hits the pto jug then hits any temp sender thats screwed into the water rail, lots of inconsistent readings that way.

    The stinger works just fine without the t-stat and pop-off.

    The REAL issue with the domestic water cooling is the self drain on the pto. The stock setup is made for somebody that doesn't want to do more than to put gas and oil in it. Problem with that is the mag sees hotter temps than it should.

    Why do you think Polaris swapped the water rail around on the msx140? Then had to restrict water to the mag. Stator cooling cover helped as well but the msx 140 has a 105amp stator.

    So before Polaris was able to make changes they left the t-stat and pop-off out of the 2000 carbed models. then in 2001 the REDESIGNED water rail went back to the t-stat with a larger pop-off valve. The new setup is listed as high flow.
    Last edited by K447; 02-02-2015 at 09:19 PM. Reason: Formatting

  9. #9
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    I can connect my temp gauge to the water rail sender or a sender attached under one of the head cover bolts on the MAG cylinder. Temps pretty much show the same thing connected either way. I prefer to read the water rail since water from all 3 cylinders is combined.

  10. #10
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    They flipped the MSX rail around for clearance issues I think. It won't fit facing the rear of the motor.

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