Continuous Alarm on Merc 150 Saltwater

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

Sleepinin is partially correct. Sorry for the delayed response. If you have figured out the gauge connections, disregard...if not, do this.
The sending units (sensors) both have a tan/blue wire connected to them and they return to the wiring harness under the dash via a single tan/blue (then) tan wire. One "is not" for a gauge and the other for the alarm.
On the alarm you should have a purple wire (ignition) and a tan wire (sensor). You want to connect to the tan wire "ahead" of the alarm and take the alarm out of the picture altogether.
From your cut/connection of the tan wire from the sensors, run this to the temp gauge "s" terminal. Make the "I" terminal up from a tap with the purple wire or other.
I agree that if you have something causing the overtemp problem (other than a bad sensor), you want to know. Thats what the gauge is installed for, to see the problem (not hear it!)

OK, so you've got me leaning towards cutting the alarm and utilizing a gauge instead.... but.... will that also cut the alert that's associated with the oil sensor warning?

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

One "important" thing that I left out. If you haven't already, your gauge must be grounded.
Find a ground point or ground wire and connect a wire to this. Run the wire to your gauge and attach it to the "center post" of the gauge. Its the terminal that holds the bracket that compresses against the gauge housing. Using a second nut as a jamb nut is best, but one with the spider washer will work.
If you don't do this, the gauge may not function. Just keep this wire clear of the other two terminals.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

One "important" thing that I left out. If you haven't already, your gauge must be grounded.
Find a ground point or ground wire and connect a wire to this. Run the wire to your gauge and attach it to the "center post" of the gauge. Its the terminal that holds the bracket that compresses against the gauge housing. Using a second nut as a jamb nut is best, but one with the spider washer will work.
If you don't do this, the gauge may not function. Just keep this wire clear of the other two terminals.

I've got the ground covered, still trying to establish if i'm going to lose the oil alert by cutting the tan+blue stripe overheat wire going to the alarm. thx for your patience.

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

Lets use another wire for the gauge and your alarm will still be active. I went out and tried this and it works. Will not take out the oil alarm.

On the alarm, you have a tan/blue wire (I said tan earlier, sorry, trying to do this from memory). In the harness you will find a tan wire and possibly a brown/white wire taped together (should run over near the alarm). Leave the alarm connected as is.
Connect the "s" terminal with the tan wire (not the tan/blue). If the "I" and ground is connected and you make the tan connection to "s", then when you turn the switch to accessory, the alarm should beep. This indicates that it is active.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

Lets use another wire for the gauge and your alarm will still be active. I went out and tried this and it works. Will not take out the oil alarm.

On the alarm, you have a tan/blue wire (I said tan earlier, sorry, trying to do this from memory). In the harness you will find a tan wire and possibly a brown/white wire taped together (should run over near the alarm). Leave the alarm connected as is.
Connect the "s" terminal with the tan wire (not the tan/blue). If the "I" and ground is connected and you make the tan connection to "s", then when you turn the switch to accessory, the alarm should beep. This indicates that it is active.

OK, i gave it a whirl. It's still setup that way, but doens't seem to provide any temp reading. I have the tan connected to the S post. the i and g posts are properly connected (as tested per my multi meter). when i turn on the switch, the alarm beeps once as expected. all good there.... but when i start the engine and let it warm up, the gauge never rises with the increased water temperature of the running engine.

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

How long is the engine running? If I run mine from a water hose to the ears, it takes a little while before mine moves off 120. Just idling, I may get 125/130 from the hose, max.
I'm sure you have a hot lead from the switch to "I" if you're testing with a meter? I pulled off the purple wire from the alarm to "I" and picked up a fresh ground from the fuse/terminal block ground terminals.
The tan wire is definitely the sensor wire to the engine. Did you find/see more than 1 tan wire in the harness?
Just checking.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

How long is the engine running? If I run mine from a water hose to the ears, it takes a little while before mine moves off 120. Just idling, I may get 125/130 from the hose, max.
I'm sure you have a hot lead from the switch to "I" if you're testing with a meter? I pulled off the purple wire from the alarm to "I" and picked up a fresh ground from the fuse/terminal block ground terminals.
The tan wire is definitely the sensor wire to the engine. Did you find/see more than 1 tan wire in the harness?
Just checking.

Again, i REALLY appreciate your advice. 9pm, and just ran out of light here in FL. I do only have one tan. I resorted to simple tests to try and progress. this thing was driving me CRAZY. first i put the multimeter on the I and G posts (with ignition on). i had a strong 12+ volts showing. then i hooked the S post up to the tan (no stripe). No action on the temp moving the needle with the motor running. Time to pull the cover of the motor. i found the solid tan wire coming from the sender. Looked easy enough, but i wanted to eliminate the issue of locating the correct wire under the dash so i cut a 30 foot section of 16 guage and wired it to the S post and all the way back to the sender. I had the tan wire entirely unplugged. Fired up the kicker and the gauge registered a good 130 on idle after a few mins. looked like i was on a roll, and i figured worse case i could run a new wire all the way back up to the center console. i then went down the path of trying to figure out why the tan wire wasn't registering.... so i tested for continuity from the sender to the tan wire under my dash. it was an open circuit, so i either had the wrong wire or it was cut somewhere. i followed the tan wire around the back of the motor and found a mysterious male tan connector around where the bundle of wires comes into the engine. looked further and found an open female connector of almost the same color. hhmmmmm. plugged the male into the female, then tested for continuity again. closed circuit. voila, the tan wire under the dash suddely has connectivity to the sender on the back of the kicker. i can only guess that when i had it in for service last year that they must have unplugged the wires to test for temp after installing the new water pump... and neglected to plug them back together again. hope that's all those two wires do when i plug them together... lol. along the way though, i seemed to have lost my tach. don't know if i could have shorted it out or what. oddly enough, it was already a replacement tach as the original one i had died. had it replaced with the new h20 pump last year, and suddenly the new one has quit working now. either i goofed something up, or it's a coincidence. just find it weird though that the darn things are so sensitive. had to give up for the night, so i still have to cut the hole for the gauge. saved the cutting for last to make sure i was going to get it to work. looks like i'm ok to pull out the saw now. as for the original problem that started this string... i haven't experienced the symptoms again. had the boat out all day yesterday and today with no overheating or low-oil alerts. will have a better comfort level though once the gauge is finally installed. Thx again for all your help!

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

I'm glad you found the disconnected wire. I was beginning to wonder myself. Don't suppose you popped the tach. fuse or pulled a wire loose. Wiring in harness is sometimes a nightmare.
Anyway, I'm glad you will have the gauge working. Trust me, it's invaluable for troubleshooting overtemp. problems. I wouldn't leave home without one
ncfish1 out.....

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

I'm glad you found the disconnected wire. I was beginning to wonder myself. Don't suppose you popped the tach. fuse or pulled a wire loose. Wiring in harness is sometimes a nightmare.
Anyway, I'm glad you will have the gauge working. Trust me, it's invaluable for troubleshooting overtemp. problems. I wouldn't leave home without one
ncfish1 out.....

hey not so quick on the departure ncfish1... any idea on what the mysterious brown+white stripe with blank end (under the dash) is intended/wired for? Also, regarding my tach, i pulled the gauge panel and it looked like all of my wires had good connections. you mentioned a potentially popped fuse for the tach, but it didn't look like there was one physically on or in the gauge. would it be somewhere else? Thx.

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

The brown/white wire I believe is for adding a trim gauge. Your tach should wire back to the fuse panel. Trace the purple wire, I believe this is the battery side of the instrument loop. The sending side of the tach is a grey wire..may want to trace this as well to see if there is a problem on the other end.
Hope this helps.