87 evinrude 50 overheat

"hi everyone, first post...i h

"hi everyone, first post...i have an issue with my 87 evinrude 50 vro. the first time i ran this motor this year i got an overheat alarm. immediately i replaced the water pump and thermostat. flushed the water line when i did this. i'm still getting the overheat horn after aout five minutes of idling. the motor starts and runs great, and it doens't even feel that hot...i can touch the head or the block for three seconds or so before it burns...i was told by a tech that this is normal. also the pee stream is cool to lukewarm. it is my understanding that the tstat should open at 140, meaning it would idle at just over this temp...and the temp sensor or sending unit would trigger the alarm at something like 200....theres no way its that hot, this would burn like heck the minute i touched anything and the pee stream would be hot as well...just a bit over 200 and there'd be steam....can any of you guys think of another possible issue...my next guess would be a bad temp sensor...am i on the right track, or should i look elsewhere...i should also mention that i do not have a factory manual yet...just orered it from kencook.com so its wont arrive for a while yet...how can i test the temp sensor for proper function to see if this really is the issue?"

"Tyler, temp senders are a pre

"Tyler, temp senders are a pretty simple device (and prone to failure). Basically it's a "switch". When the temp is below "x" degrees the switch is "off" as the temp rises it starts to close. When it reaches it's "danger temp" it's completely closed, completing the circuit to your warning horn or buzzer - which then goes off.

Here's a little diagram from a Merc manual. Although not specific to your motor obviously, it gives how to test these things...

You need a pot of water on the stove, a thermometer and an ohm meter. As the sensor heats up you can watch the resistance drop to near zero (starting with significant resistance if it is working correctly) - dropping to zero before the water gets above say 180 or so, indicates a toasted sensor...
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