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  1. #1
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    Default 1989 88hp Evinrude; Hot or NOT?

    I have an 89 88hp evinrude that has been showing that it is running hot on the gauge, but when I touch the head it feels only warm at speed and hot but I can hold my hand on the heads at idle. The gauge also moves some when I change trim angle. The motor runs fine and shows no signs of distress. There is a small grounding wire that goes between the powerhead and the midsection that has broken off. I'm wondering if that is causing the gauge to read high due to a poor ground?

  2. #2
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    Usually being able to hold your hand on the head for a 1, 2, 3 count, or being able to splash water on the head without having it sizzle, are signs that you are not overheating. Although, an infrared thermometer would be able to tell you exactly what temp you are running at. Is you overheat alarm functioning? Tested it lately?

    BTW, what temp does it say you are running at?

  3. #3
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    It's up to like 210. Yet I can hold to 3 on the head @ the dock.

  4. #4
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    Quote Originally Posted by pennyanman1 View Post
    It's up to like 210. Yet I can hold to 3 on the head @ the dock.
    I suggest you buy an infrared thermometer - you can usually find one for $25 or so. Then you can verify your temperature gauge.

    You should also test your overheat alarm.

    My guess is that it is a gauge problem, but I'd try to verify before buying a new one.

  5. #5
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    Your engine has 143 degree thermostats in it. They should open at 143, so a normal idle temp should be around 150-155. The hot horn should sound at 211 and will silence when the head temp gets back down to 175. If you are truly running at 210, that is too hot. The engine has two stats, one for each side of the block. As dajohnson said, you need to verify just what the temp of the engine really is, as well as checking the two head temp sensors. Temp gauges are not always accurate-I've seensome that are 15 degrees off, so the infrared gun is the best.

  6. #6
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    No hot horn, but I'll check that tomorrow (have the OEM manual). I was also wondering what I should see on the gauge if I jumper from the top of the sender to the block with the key in "run". I'm guessing it should read at the bottom of the range. I'm still a bit suspicious of grounds. What is suggested regarding making sure the guage is properly grounded? It is a 40 year old boat with 40 year old wiring, so it is feasable that the guage is ok and the issue is else where. In any case, I highly doubt the motor is suspect, as I have plenty of water from the pee hole and the motor ran over 40 miles at 4500 rpm yesterday without a hic-up.

  7. #7
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    Default Re: 1989 88hp Evinrude; Hot or NOT?

    Quote Originally Posted by pennyanman1 View Post
    No hot horn, but I'll check that tomorrow (have the OEM manual). I was also wondering what I should see on the gauge if I jumper from the top of the sender to the block with the key in "run". I'm guessing it should read at the bottom of the range. I'm still a bit suspicious of grounds. What is suggested regarding making sure the guage is properly grounded? It is a 40 year old boat with 40 year old wiring, so it is feasable that the guage is ok and the issue is else where. In any case, I highly doubt the motor is suspect, as I have plenty of water from the pee hole and the motor ran over 40 miles at 4500 rpm yesterday without a hic-up.
    You can easily test the gauge's ground by taking a DC volt reading between the ignition (purple wire) terminal on the gauge and the ground TERMINAL on the gauge with the key on. Don't take the reading between the ignition terminal and the grounding terminal strip, etc. You want to test if the wire connected to the gauge's ground terminal is actually grounding it. If you see "battery voltage" (~12+ volts) you know that the wire attached to the ground terminal on the gauge is well grounded.

    You can also check the adequacy of the wire that goes between the sender on the engine and the gauge by testing resistence from the gauge end to the sender. Should be very, very small.

    If in doubt, replace ground and sender wire and see if that helps.

    To test the gauge itself, one test you could try, assuming the purple/ignition , ground, and sender wires are all good and on the proper place on the gauge:

    1 - cold engine, key on: gauge should read 0 - or whatever is considered normal for the cold engine. At or near bottom of the gauge's scale.

    2 - cold engine, key on, ground the "S" (sender) terminal - gauge should peg at highest reading.

    #2 would indicate that the gauge would read properly IF (this I'm not sure of) the sender on the engine is intended to move toward lower resistence when the engine heats up, and eventually approach zero resistence when it's really hot. This is what you're simulating at the gauge by grounding the sender wire - zero resistence.

    This is my guess as to how it is designed to work. I guess it could be opposite in that the resistence is 0 or low when cold and high or infinity when hot, in which case the gauge test would be opposite.

    Most gauges come with specs on what the resistence should be for the sender at the two extremes of it's operation and how to test the gauge (like the example above). But with your old gauge, that info might not be available. you can try the above and see what you find.

    Just thinking about it... again kind of guessing... if your gauge operates properly on the two tests above, and if the sender wire is good, but you still think it is reading too high: my guess then is that the sender is bad - it is not moving through the resistence range as it should be for a given temperature. The only ways I can think of testing this are:

    take the sender off and test resistence as you heat it to known temperatures. This however would require that you know what the resistence should in fact be at those temps. This info might be available - it is for newish gauges in the instruction / troubleshooting info. But for an older one like yours??

    OR: double check the temp with the infrared thermometer. If the gauge itself tests out OK, but the IR thermometer shows it is reading inaccurately, you can assume the sender is bad.

    Chances are you will have to buy a sender + gauge combo anyway -- so your path of least resistence, IMHO!!, is to (a) test ground of the gauge and the wire to the sender and (b) check actual temp with an IR thermometer. IF properly gounded, good sender wire, but not accurate, just buy a new gauge and sender.

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