Help on Evinrude alarm

OK here's one for the Brain Bank. I have a 1989 120 HP Evinrude. Currently Engine runs great but after a few miutes running I get a constant alarm. Can let engine sit for 20 minutes or so and alarm will go away. Looks like overtemp but Have excellent water flow, and no fuel restrictions - engine continues to run with no obvious effect. According to the Evinrude shop manual there are four functions for the alarm, Overheat - continuous alarm, No Oil - continuous short pulses, Low Oil - short pulse every 20 seconds, Fuel Restriction - continuous tone at or near full throttle.<br /><br />As stated I have excellent water flow, no apparent fuel restriction, good oil flow.<br /><br />Would certainly appreciate any constructive comments.

Re: Help on Evinrude alarm

The overboard water indicator just shows there is water flowing. What does the cylinder heads feel like?

Re: Help on Evinrude alarm

Both heads feel hot, not to hot to touch but they do show some heat. If the flow indicator tube only shows flow, how else can it be checked?

Re: Help on Evinrude alarm

Andy, i had a constant alarm after 4000 rpm i would slow down it went away, found out my pickup was plugged. There was no miss or anything like it was a restriction.

Re: Help on Evinrude alarm

I'd replace the thermostat and then see what happens. You might have flow, but if the thermostat isn't opening, it isn't going to help you much.<br /><br />Good luck!<br /><br />Brew

Re: Help on Evinrude alarm

When the alarm sounds disconnect the heat sensor then the fuel restriction sensor. At least that will tell you which it is.<br /><br />How much water presure do you have?

Re: Help on Evinrude alarm

To All, thanks for the replies and ideas. I believe I will go with Dhadley's suggestion to try to narrow it down first then on to part swapping.<br /><br />Thanks again, I let everyone know what it turns out to be

Re: Help on Evinrude alarm

Further Check with temp gun revealed that upper cylinder on right side, when viewed from rear, is running about 8 degrees above the lower on the same side. Both are about 20 degrees above the left side when viewed from rear. This seems to indicate a bad thermostat. Does this sound about right. I ran the boat for right at 20 min at the dock, alternating between an idle and about half throttle both in and out of gear. <br /><br />Side note, None of the temps ever exceeded 147F

Re: Help on Evinrude alarm

the thermostats only come into play at below 2000 rpms or so. There are springs on the thermostats that the pressure lifts the stats off their seats and bypasses the thermostats at cruising speed.<br /><br />If it overheats at idle then the stat would be the first thing to check. if it overheats running at cruising speed there has to be more to it. <br /><br />I'd pull the thermostat and backflush through the thermostat port.<br /><br />Edit:<br />I just read the sidenote.<br />147* isn't hot and the starbord bank tend to run a little warmer.<br /><br />Pull the overheat sensor wire on that bank and see if the alarm stops. if it does, I'd check the sensor in a pan on the stove. if you rings out at 147* the sensor is bad