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Overheat alarm

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capn_morgan

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"Got a 1990 Evinrude 70hp that

"Got a 1990 Evinrude 70hp that the temp alarm is going off. It pees a steady stream out the telltale and I can take the cover off and put my hand on the exhaust cover - it just doesn't seem hot. It will run forever under 3000rpm without an alarm and it hasn't alarmed at 5400wot (although it doesn't run much there as it's a pontoon boat.) But around 3500-4000 it will occasionally go off. Let it sit a minute, it starts right up with no alarm. One time we were docked at a buddy's place for about 15 minutes and when I took off, it alarmed within 30 seconds. Doesn't seem long enough to even get warm, much less hot. I did replace the temp switch with a new one and it still happens. Could it be wiring and the vibration at that rpm sets it off? Is it possible the top carb is running lean at midrange since the switch is on the top cylinder? I do have carb kits for it, but prolly won't get them in this season since it's almost over around here. Any thoughts?"
 
"when,wAS the last time,..u in

"when,wAS the last time,..u installed a complete,new water pump kit.....i think,...its time.."
 
"I just got the motor last yea

"I just got the motor last year. Came from an older fellow who hadn't used it much in a long time. I'd bet it's all original. If it's peeing a strong stream, doesn't that mean it's pumping good?"
 
"Ok, I had another thought. I

"Ok, I had another thought. I assume the telltale comes from before the t-stat otherwise nothing would come out of it when it's cold. Could it be a bad t-stat maybe?"
 
"ur on the right track,..u say

"ur on the right track,..u say it has'nt been used in a while,etc...replace the pump w a compl kit,is the first thing to do..it would'nt hurt to inst a therm kit also..."
 
Your engine has a thermostat t

Your engine has a thermostat to control engine temp from idle to when there is enough water pump pressure to push the bypass valve off its seat and cold water can flow through the engine.

You need to remove the thermost ass and bypass valve and renew them.
 
"I always install water pressu

"I always install water pressure gauges on my OMC engines. With a new waterpump, mine read about 15 at idle on muffs. Every year you can see this number decrease. After about two to three years, I replace the pump. Stream looks just as strong to me when it needs a pump as when I just replaced it. I would start with a pump kit as suggested."
 
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