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  1. #1

    Exclamation Can a run without a thermostat????

    Doesn anybody run without a thermostat? I took my out, bc a mechanic told me i did not need one. However, i do not want to mess anything up!!! He said it just make your engine warm up faster? What can happen if i operate my outboard without a t-stat??/ Thanks guys!!

    *tOOK IT OUT THIS WEEKEND AND IT SEEMED TO RUN FINE WITHOUT ONE...........

  2. #2
    Supreme Mariner
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    Default Re: Can a run without a thermostat????

    What motor? Can you? Sure (obviously). Should you? Nope.

    Don't know where your "mechanic" got his training but without one the motor should take longer to warm up to the proper operating temp. If it ever does. A lot depends on what motor it is.

  3. #3

    Default Re: Can a run without a thermostat????

    I disagree, I had a a guy who worked on motors for years, approximatley 45 years, tell me unless you are a duck hunter, you don't need one. The only time I was told that it is a neccessity is when you operate your motor in cold weather. I have several motors rangeing from a 150 hp down to a 6 hp and none have themostats in them.

  4. #4
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    Default Re: Can a run without a thermostat????

    Quote Originally Posted by rick_l View Post
    I disagree, I had a a guy who worked on motors for years, approximatley 45 years, tell me unless you are a duck hunter, you don't need one. The only time I was told that it is a neccessity is when you operate your motor in cold weather. I have several motors rangeing from a 150 hp down to a 6 hp and none have themostats in them.
    You need to find a new mechanic who isn't ignorant. A 2s motor run w/o a thermostat will run too cold and carbon up.
    Jim

    ===============================
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    OEM shop manual: outboardbooks.com or Ebay

  5. #5
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    Default Re: Can a run without a thermostat????

    True. And those with a Quick Start type circuit that's goverened by temp may never come out of Quick Start which makes shifting pretty hard on gears going into gear and just plain hard coming out of gear.

    Some motors will actually overheat. The water doesn't fill the block and the top cylinder(s) can overheat. Some motors need the t-stat as a restriction to create a full cooling system. With the t-stat gone the water exits quicker than it comes in. Not good for motors with water cooled regulator / rectifiers even if it doesn't overheat.

    Some motors with EFI or DFI just plain won't run right without a t-stat.

    Some motors may wear out the rings prematurely. Granted you might be talking the difference between 2500 hours and 3000 but it can still happen.

    There are a lot of race motors that don't have t-stats. But they have some sort of device to restrict the water flow and that simulates a t-stat and governs temp and pressure.

    Many times we've seen new pistons damaged on a fresh rebuild only to find out the motor had no t-stat(s). Piston skirt to cylinder wall clearances are based on a given heat transfer rate.

    Again, can you run without a t-stat? Sure. Should you? That's up to you.

  6. #6
    Admiral CATransplant's Avatar
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    Default Re: Can a run without a thermostat????

    Quote Originally Posted by rick_l View Post
    I disagree, I had a a guy who worked on motors for years, approximatley 45 years, tell me unless you are a duck hunter, you don't need one. The only time I was told that it is a neccessity is when you operate your motor in cold weather. I have several motors rangeing from a 150 hp down to a 6 hp and none have themostats in them.
    Lots of guys say lots of things. Your guy was wrong. Yes, your outboards will run, but they'll never get up to proper operating temperature, and that's not good for the engine, which was designed to operate with the thermostat keeping the temperature where it's supposed to be.

    Thermostats started being put in Johnnyrudes in the late 1950s (1958, if my memory serves.) The cooling system was redesigned for the thermostat. For example, the 1958 RDS-20 was the first of the 35hp big twins to get a thermostat. At the same time, they switched to a water pump housing with two water lines from the pump to the engine, rather than just one. Cooling system redesign. Running that outboard without a thermostat wasn't the same as running a 1957, which had no thermostat by design.

    I figure the folks at OMC pretty much knew what their outboards needed, so if there's supposed to be a thermostat in one, it's probably because they designed the engine to run best with one in place. I don't think that second-guessing the designers makes any sense, frankly.

  7. #7

    Default Re: Can a run without a thermostat????

    Okay, you guys made alot of sense. I believe my guy is wrong. So I'm going out to buy my thermostat. Never quit learning.

  8. #8
    Seaman Apprentice aJohn79's Avatar
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    Default Re: Can a run without a thermostat????

    Question here....
    Going back to the part # for the 2.3L OMC thermostat. I checked the link on the first reply and came up with part # 3853799. This thermostat is set to open at 160. Looking at my SELOC manual, for the Ford 2.3L, the thermostat temp is 193. Can anyone make sense of this? I can't find a thermostat that opens at 193 for this engine?
    1990 17' Four Winns w/ 2.3L Ford OMC Cobra
    (Pertronix Ignitor II and coil electronic ignition mod)

  9. #9
    Seaman Apprentice aJohn79's Avatar
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    Default Re: Can a run without a thermostat????

    oopps... sorry, wrong thread.
    1990 17' Four Winns w/ 2.3L Ford OMC Cobra
    (Pertronix Ignitor II and coil electronic ignition mod)

  10. #10
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Can a run without a thermostat????

    (Thermostat Purpose)
    (J. Reeves)

    Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperture to compensate for the distortion.

    With the thermostat removed, the difference in temperture between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

    The thermostat in your car isn't there simply to have the heater function properly..... think about it.

  11. #11

    Default Re: Can a run without a thermostat????

    Engineers are engineers for a reason. I live in Florida and people here think that if you run your car without a thermostat, it will run cooler, but the opposite is true. It actually runs hotter, because the thermostat is not present and that allows the coolant to continuously circulate through the system, therefore not allowing it to stay in the radiator to cool down.

    Now, boat motors will do just the opposite, in theory, by not having a thermostat, then the operating temperature will probably be alot lower than the norm, simply because it does not recirculate the water, but is bringing in cool water at al times, so your engine will not run at full efficiency. Damages may occur, etc, etc. Pt a thermostat back in.

    If it was designed to be there, make sure it was there. This is true with anything.

  12. #12
    Moderator QC's Avatar
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    Default Re: Can a run without a thermostat????

    Remember thermostats control minimum temperature, not max. Removing one will never solve an overheat on any engine unless the one removed was stuck closed. And, as ducky mentioned, removing one can actually cause an overheat as the water internal to the engine can bypass the cooling circuit, whether that is a heat exchanger, radiator or the lake . . .

    When manufacturers conduct a cooling audit on any engine and vehicle combo, they actually use thermostats that are stuck open as this allows them to test the maximum cooling capability. If they remove it, again, they get bypass instead of 100% flow through the seperate cooling circuit, aka the radiator, heat exchanger or lake/ocean . . .

  13. #13

    Default Re: Can a run without a thermostat????

    how do you know if the thermostats are stuck open?

  14. #14

    Default Re: Can a run without a thermostat????

    Quote Originally Posted by duckynme View Post
    people here think that if you run your car without a thermostat, it will run cooler, but the opposite is true. It actually runs hotter, because the thermostat is not present and that allows the coolant to continuously circulate through the system, therefore not allowing it to stay in the radiator to cool down.
    According to that logic, the coolant also wouldn't stay in the engine long enough to absorb heat.

    Running w/o a thermostat may not allow the engine to reach it's optimum temperature, and that will result in poor fuel economy, and possible engine damage.

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