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.

As stated I have excellent water flow, no apparent fuel restriction, good oil flow.

Would certainly appreciate any constructive comments.

Andy...It is a weak water impellar because if you look at were the water outlet is which is a the bottom of exhaust plate and the sensor is at the top of the cylinder head the block is not filling up all the way change the impellar or have it looked at it could also be a stuck thermostat ......OPTI

I have an 85HP Evinrude and had the same thing happen 2 weeks ago. It's the impeller. I had a guy in Carrollton replace it for $75 which included parts and labor. His name is Jeff and his # is 214-505-1687 Texas Boat Service and Repair. He will even drive to your house!!

May not apply here, I have 85 Yamaha, it would run all day at 3/4 speed, but if I opened it up the alarm would go off for overheat...I changed the water pump entirely, changed thermostat and pressure control valve, it still did the same thing...I thought I had good waterflow, even a professional changed the water pump and tested it in the water well for me...

In the end another professional Uamaha dealer, Texas Marine in Conroe, found the water line from the water pump to the thermostat was fouled up with "gunk" and after cleaning it out, water flow increased even more and it fixed the problem...good luck, it can be frustrating...

I had the same problem, would troll all day long but when power was applied it would run about 1/2 mile and the warning horn would sound. After being in 2 shops and 6 weeks latter they got it fixed.Water punp replaced ,both termostats, heads removed an new water flow tubes installed. ONLY cost me $1100. It was a Johnson. Good luck!!

Thanks to all. Lot to think about. As a side note, I just replaced the water pump housing and impeller last summer and have a very strong stream coming out of the hole. Im beginning to wonder if changing the thermostats and temp sending units as Big Bill suggested might help.
Does anyone know of a local place that sells the Thermomelt Sticks?

Could be thermostat/implller or could be bad tac. My oil light came on nothing to do with anything bad just internal short in the tac.

Because of age I would change the water diverting tubes. Have seen them bad on older OMC motors. You are on right track with sticks, just check differant areas of cylinder heads. NAPA has them. Best to use a temp gun if you can borrow one. Most auto repair, boat repair and machine shops have one. Good Luck

Gary,

have borrowed a temp gun to check it with. The water diverting tubes you spoke of, are they the external hoses that criscross the engine on the rear?

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.

Side note: None of the temps ever exceeded about 148 F.

Andy..... Get the horn to go off and start unplugging sensors if you unplug one of the head sensors and it goes off and the temp is no higher than 148 then you have a bad temp sensor Sensors to unplug are the two head sensors the oil tank with looks like a lamp cord the trusty old VRO witch is the round plug with four wires and the fuel vaccum switch This will get you headed in the right direction.....OPTI