I?m pretty sure I?ve got a bad temp sensor on the port side head on my 1977 Evinrude 140 ?bubble back? Cross-flow motor. After getting an alarm a year or so back I had the water pump replaced along with both thermostats by a reputable boat mechanic. After that I would still get an occasional alarm but I could see the flow of water and I checked the temperature as described below so I didn?t worry with it.
A week or two ago was the first time out this season for this motor because I moved it to another boat and the alarm went off as soon as the motor got warm so I shut it down.
I checked the water temperature by inserting a long ?K? style thermometer lead in the leaving water from each head on its way to the thermostat housing. I loosened up the hose clamp and ran the thermometer lead in-between the stub and the hose on the short 90 degree hose that connects these. With the leads plugged into an electronic meter, I read anywhere from 120 ? 145 degrees depending on load and speed on each side. High speed was on the 120 end and low speed was 130?s to 140 and never got to 150 degrees. So I disconnected the buzzer for the remainder of that test run.
Today with the sensors back in the circuit the alarm did the same thing so I disconnected the sensors one at a time and it was the port side giving the trouble. I then bolted the temperature leads to the side of the head under a mounting bolt where a clamp attached on the port side, and under the negative battery cable on the starboard side. Both spots were as close to the cylinder as I could get with a mounting bolt. With 5 foot leads we monitored the cylinder temperature under various loads and the temperature range was almost identical to the water temperature on each side. I unhooked the one sensor and ran the rest of the trip without an alarm.
Is 120 ? 145 in the right temp range? Is this sensor is shot?
If so, how do you remove these sensors? They look like there?re inserted in a thermometer well and I?m not sure if the cylinder head holds them in or not. They may just pull out. Any input to sensor removal and replacement on this model?
Thanks.
PS,
I know I could have just asked if 125 ? 145 was the right range, and how to remove the sensors. However, I believe this method of checking temp is accurate and maybe it will help someone else with overheating problems. It?s just not the same on a garden hose with muff?s. Many if not most multi-meters will accept ?K? style thermometer leads (some meters require an adapter) and if you get a long lead, it?s a thousand times safer than trying to read the engine temp with a infra-red radar gun thermometer while you are running.
A week or two ago was the first time out this season for this motor because I moved it to another boat and the alarm went off as soon as the motor got warm so I shut it down.
I checked the water temperature by inserting a long ?K? style thermometer lead in the leaving water from each head on its way to the thermostat housing. I loosened up the hose clamp and ran the thermometer lead in-between the stub and the hose on the short 90 degree hose that connects these. With the leads plugged into an electronic meter, I read anywhere from 120 ? 145 degrees depending on load and speed on each side. High speed was on the 120 end and low speed was 130?s to 140 and never got to 150 degrees. So I disconnected the buzzer for the remainder of that test run.
Today with the sensors back in the circuit the alarm did the same thing so I disconnected the sensors one at a time and it was the port side giving the trouble. I then bolted the temperature leads to the side of the head under a mounting bolt where a clamp attached on the port side, and under the negative battery cable on the starboard side. Both spots were as close to the cylinder as I could get with a mounting bolt. With 5 foot leads we monitored the cylinder temperature under various loads and the temperature range was almost identical to the water temperature on each side. I unhooked the one sensor and ran the rest of the trip without an alarm.
Is 120 ? 145 in the right temp range? Is this sensor is shot?
If so, how do you remove these sensors? They look like there?re inserted in a thermometer well and I?m not sure if the cylinder head holds them in or not. They may just pull out. Any input to sensor removal and replacement on this model?
Thanks.
PS,
I know I could have just asked if 125 ? 145 was the right range, and how to remove the sensors. However, I believe this method of checking temp is accurate and maybe it will help someone else with overheating problems. It?s just not the same on a garden hose with muff?s. Many if not most multi-meters will accept ?K? style thermometer leads (some meters require an adapter) and if you get a long lead, it?s a thousand times safer than trying to read the engine temp with a infra-red radar gun thermometer while you are running.
