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  1. #1

    780 without thermostat will overheat?

    I just wanted to know if my 780 will overheat without a thermostat reason being is that my SL750 could run at idle on the hose and I could touch the jugs and they werent even hot at all but I dont know if it had a thermostat and its been since sold and the Guy rides the crap out it


  2. #2
    seaobin's Avatar
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    thermostat is for the other direction. If you ride in cold water, it closes to keep the engine warmer. It stays open once the water heats up. If you run your engine too cold it will run less efficiently. if you remove the water rail and thermostat, some guys recommend restricting the flow through the heads to keep the cylinders warmer.

    I run mine wide open

  3. #3

    780 no thermostat

    I guess my SL 750 didnt have one because it ran cool on the hose .You said you run wide open meaning no thermostat right.I think I will try it.My jugs on this 780 have been bored out considerably and I think it would be good for it.What water temps do you normally run in?We down in Tx.range around 82 to 87 on hot days.

  4. #4
    seaobin's Avatar
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    no restrictors, no thermostat

    runs hot, but not burning
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  5. #5
    1996 SL900 & SL700 turk0004's Avatar
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    Quote Originally Posted by seaobin View Post
    no restrictors, no thermostat

    runs hot, but not burning
    Did you spray paint your exhaust and head covers? Is there a post about how you did that?

    Turk

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by johnnyrod View Post
    ...my SL750 could run at idle on the hose and I could touch the jugs and they weren't even hot...
    When connected to the reverse flush hose connection on the water manifold (water bar), the water flow direction through the engine is reversed.

    It is intended primarily to flush dirt and salt accumulation out of the engine cooling passages. It is not designed to provide normal cooling water flow through the engine.

    The reverse flushing water does NOT flow through the thermostat (if it is in place), since the cold garden hose water is entering right where the thermostat is located. So the thermostat stays closed when running on the hose.

    Also, the water flow through the engine is reversed, so the water exits via the jet pump cooling water inlet, inside the jet pump nozzle.

    If the thermostat and/or the pressure controlled spring plunger is removed from the thermostat housing, then the water flow from the reverse flush connection can travel both ways.

    One way is directly through the thermostat housing (since some of the parts are not there to prevent the flow), and out the back of the watercraft. That water does nothing to cool the engine. The other flow path would be through the engine, in the reverse direction, and exits via the jet pump cooling inlet.

    If your engine ran cool on the reverse flush hose at idle, that doesn't tell you much about how it will run when in the water.

    Without a thermostat in place, the engine should run normal (about 140F) or cooler water temperatures, but not close to overheat. If it runs too hot, then something is restricting water flow.

    Normal engine cylinder head water temperatures (140F range) would mean you can hold your hand on it for a few seconds without burning yourself.

  7. #7
    seaobin's Avatar
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    Quote Originally Posted by turk0004 View Post
    Did you spray paint your exhaust and head covers? Is there a post about how you did that?

    Turk

    http://greenhulk.net/forums/showthre...highlight=blue

    Just used high temp engine paint

  8. #8
    1996 SL900 & SL700 turk0004's Avatar
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    very nice

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