My temperature gauge has not been working, so while fixing my fuel level indication I am hoping to tackle this one also. Having a little troubling finding reliable info for troubleshooting. Motor is a 2006 Yamaha 150TXR, basic two stroke nothing fancy. Not sure where temp sensor even is on motor - is this it (the thing w/ tan pigtail wire on top? Looks to be about the right place based on parts schematics.
However, something seems odd about this wire - it doesn’t connect to anything on motor and isn’t bundled in with any others. Almost like it was added on. Can’t find a similar colored wire in console/gauge cluster but it might have an intermediate splice somewhere I can’t see. You can see how it runs in this photo:
Gauge cluster has power, haven’t tried gounding/shorting anything to see if meter moves because I wasn’t sure what is what. Any suggestions how I might be able to figure this out?
update - been researching this, and seems that I have a generic aftermarket single-wire temp sending element rather than the Yamaha spec part, which has two wires (yellow/black).
Seems odd - why would they (either boat manufacturer or some previous owner) have pulled out the Yamaha sensor for this? Simplicity in wiring temp gauge? Replacing dead one? Or did motor not come standard w/temp probe?
I don’t know about the 150, but the 70’s and 90’s didn’t come standard with a temp gauge sending unit. Have to buy it optional. I put in a temp gauge for my 70, then learned I also needed a sending unit for it. Since it has a built in over heat alarm anyway, I said the heck with it and never hooked it up.
well i think I got it figured out, there is a separate temperature sensor that matches the pictures of Yamaha temperature probes I’ve found. It seems to tie directly into the CDI unit and nothing else. Temp sensor on top of motor IS wired directly to gauge, as CL said looks like probably comes w/gage system not motor.
I bench tested all the parts, everything seems to work:
meter works (full scall to 240F when grounded, also hooked up a variable resistor and can manipulate across full range by varying resistance)
gage cluster has power (verified w/multimeter, fuel and voltage meters work)
temp sender resistance varies between about 450 ohm at room temp to 55 ohm in boiling water, don’t know exact specs of this one but that seems reasonable based on others I’ve found
But when I hook it all up, gauge was still pegged low even w/motor warmed up on muffs. Going to check all connections and try to find a way to check continuity of wire coming from motor to console.
Also think that the way sender was installed is not correct - found several mentions that you shouldn’t use sealant on threads (which makes sense, because signal depends on ground path through motor) and mine was gobbed w/pipe sealant of some sort. Going to clean all that up, reinstall, and see if that helps.
While working on this I also found a few other unpleasant surprises - mystery bolt laying in bottom of cowling, and broken clip from VRO pump to throttle. That could have been a disaster if I hadn’t noticed.
I also suspect my alarm buzzer is not working - is there an easy way to test? Shouldn’t it alarm w/key on and safety lanyard removed? Mine doesn’t.
Boss is making put my toys away though, so have to finish up next weekend.
there is a difference between the alarm activation “switch”, and the temp sensor.
they are 2 different devices.
the “switch” comes standard on the motor
the sensor to make a temp gauge work is an add on part
your motor has both. the 2 wire overheat switch is right beside the top spark plug with tan shield around it
alarm will not sound with just key on and lanyard removed
try to start it with the lanyard removed and it should sound.
if clip fails, oil pump automatically goes to WOT oil, so only bad thing to happen would be smoking, fouled plug, and wasting oil.
So I got temperature gauge working (mostly). Found a home for the mystery bolt (went to hold down for wiring harness, nothing major) and replaced VRO clip.
While trying to remove the pipe sealant/5200/whatever gunk a previous owner (or “mechanic”) used to seal the temp sensor in, I realized why they might have done that. The threads in the aluminum block that the brass sensor screws into are in pretty bad shape - corroded and/or stripped to the point I am afraid if I try to tighten the sensor too much they may give out completely. Any ideas? Anything I can do to at least slow the rate of corrosion between the dissimilar metals without affecting the electrical connection between them?
and as always, one project leads to another. Since I was working on cooling system anyway, I pulled thermostats to take a look. One was stuck open, the other was stuck shut. Doh! Replacing both.
I plan to pull and test the temperature alarm switches, just to be sure they work.
Also, tested alarm buzzer as Chris V suggested and no alarm. What now?
I will say, this motor is a hacker… it’s apparently been running around in a pretty sketchy condition and other than some smoky idling hasn’t complained a bit! (although I guess that could be because alarm is not working…)
Going to check all connections and try to find a way to check continuity of wire coming from motor to console.
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