Continuous Alarm on Merc 150 Saltwater

[joebiii]

I have an '03 Merc Saltwater 150. Serviced last summer, with waterpump replaced. Of course, no problems until out on the river late at night with another family (5 kids) on the boat. After riding through the nowake area of about 1 mile, attempted to plane. The warning alarm sounded (continuous). Water was streaming out of the rear, which appeared to be normal waterpump flow. it did seem to be smoking more than standard exhaust. I turned off the engine for a min, restarted. after a few minutes same symptoms. finally was able to proceed in this manner enough to make it to the dock. any ideas?

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

I would suggest purchasing and installing a gauge in leu of sensors. Own a 150 saltwater (2000 model) that constantly signaled problems when there were none. A gauge will tell you if there is a problem and then you can go to the next step. The only things that can cause alarms are these: thermostats, pump, relief/poppet assy or restricted water passages. My primary problem with the 150 is t'stats and basically due to saltwater corrosion. Your merc should operate about 150 degrees fully loaded (max. 180 with warm water conditions). You can purchase a laser temp. tester and measure temp's. at each head. This will tell if your merc. is overheating. Temp. sensors do nothing but provide boat service businesses with plenty of work (trust me, I've been there).

 

[cowboy133]

Re: Continuous Alarm on Merc 150 Saltwater

mine did the same thing..Put a new oil tank on fixed the problem

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

mine did the same thing..Put a new oil tank on fixed the problem

I was running a low on oil, down to about 1/2 inch in the tank. the thing throwing me off though (leading me to believe it is not an oil problem) is that the backup resevoir (on the engine) was still full. the alarm was continuous as well, as opposed to the oil-low beep warning. i added 2 gallons of oil. was unable to duplicate today, although the events of last night crushed any sense of confidence in my previously issue-free history with this kicker.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

I would suggest purchasing and installing a gauge in leu of sensors. Own a 150 saltwater (2000 model) that constantly signaled problems when there were none. A gauge will tell you if there is a problem and then you can go to the next step. The only things that can cause alarms are these: thermostats, pump, relief/poppet assy or restricted water passages. My primary problem with the 150 is t'stats and basically due to saltwater corrosion. Your merc should operate about 150 degrees fully loaded (max. 180 with warm water conditions). You can purchase a laser temp. tester and measure temp's. at each head. This will tell if your merc. is overheating. Temp. sensors do nothing but provide boat service businesses with plenty of work (trust me, I've been there).

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

I would suggest purchasing and installing a gauge in leu of sensors. Own a 150 saltwater (2000 model) that constantly signaled problems when there were none. A gauge will tell you if there is a problem and then you can go to the next step. The only things that can cause alarms are these: thermostats, pump, relief/poppet assy or restricted water passages. My primary problem with the 150 is t'stats and basically due to saltwater corrosion. Your merc should operate about 150 degrees fully loaded (max. 180 with warm water conditions). You can purchase a laser temp. tester and measure temp's. at each head. This will tell if your merc. is overheating. Temp. sensors do nothing but provide boat service businesses with plenty of work (trust me, I've been there).

With regards to the recommended guage(s), i'm assuming you suggest a temp guage. are the engines pre-tapped to accept it, or is this something i'll need to have added at my next service?

 

[sleepinin]

Re: Continuous Alarm on Merc 150 Saltwater

I'm not sure about your 2003 model , but on my 1999 150 saltwater there are two temp senders. One is on the starboard side and it activates the alarm. The other is on the port side and it goes to the temp gauge. If you don't have a temp gauge the wire is probably in the harness under you dash and not connected to anything. It's likely tan or tan/blue stripe. Since they are two seperate systems you can correlate the alarm with the temp gauge and see that you are not getting a false reading. A water pressure gauge can be more beneficial because it will tell you if the poppett is working corretly and what kind of pressure your getting after the thermostats.

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

For temp gauge installation on your 150, check the wire color at the sensor(s); I believe it is brown with a blue stripe. Under your dash, locate the alarm and pull the matching wire. This connects to the gauge along with a ground.
Purchase or have installed a TeleFlexMorse - Vector Water Gauge #120240F. You can get a 2", black face with blue/white temp. readings. Can purchase through most marine suppliers. Cost is about $30.00.
After connecting, your engine should operate at 160 degrees constant after t'stats have opened and under load. If you find higher operating temps than this, its time to start worrying (just kidding).
You will at least be relieved or know that there is or is not a problem and piece of mind knowing what your engine is doing rather than depending on some alarm..

 

[kpostman]

Re: Continuous Alarm on Merc 150 Saltwater

I just had the exact same problem with a 250 saltwater. It was a bad float/ sending unit in the "on engine" oil tank. The whole tank was replaced as you can't just change the float. The parts were fairly cheap, $70 I think. The labor was a bit steep though. Chang it your self and save.
Once it was replaced, the alarm went away.

 

[insomniac71]

Re: Continuous Alarm on Merc 150 Saltwater

steady alarm on my merc means overheating. first trip out this season i had the same problem with the steady alarm but the temp gauge was reading normal. replace those THERMOSTATS, there are 2, 1 on each head at the top about $9 each.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

I'm not sure about your 2003 model , but on my 1999 150 saltwater there are two temp senders. One is on the starboard side and it activates the alarm. The other is on the port side and it goes to the temp gauge. If you don't have a temp gauge the wire is probably in the harness under you dash and not connected to anything. It's likely tan or tan/blue stripe. Since they are two seperate systems you can correlate the alarm with the temp gauge and see that you are not getting a false reading. A water pressure gauge can be more beneficial because it will tell you if the poppett is working corretly and what kind of pressure your getting after the thermostats.

do i have to install any sending unit to provide the signal for the water pressure to the gauge?

 

[sleepinin]

Re: Continuous Alarm on Merc 150 Saltwater

Yes,
You actually cut in a tee(not a sending unit) and then run a tubing from the tee at your engine up to the gauge in your dash. The parts should come with the gauge. There should also be instructions in there.

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

For temp gauge installation on your 150, check the wire color at the sensor(s); I believe it is brown with a blue stripe. Under your dash, locate the alarm and pull the matching wire. This connects to the gauge along with a ground.
Purchase or have installed a TeleFlexMorse - Vector Water Gauge #120240F. You can get a 2", black face with blue/white temp. readings. Can purchase through most marine suppliers. Cost is about $30.00.
After connecting, your engine should operate at 160 degrees constant after t'stats have opened and under load. If you find higher operating temps than this, its time to start worrying (just kidding).
You will at least be relieved or know that there is or is not a problem and piece of mind knowing what your engine is doing rather than depending on some alarm..

ncfish1 - I bought the gauge. The one i have is a Teleflex Morse Vector 56933P (for code D sender vector line). I located the alarm, and it did have a light brown+blue stripe wire connected to it. i followed the wire to where it ended in a cut end - nothing connected to it. i assumed this is where the guage would be attached. i attached the available 'cut end' wire to the S post on the gauge. i then attached the ignition and ground. upon turning the key on, the alarm continously sounds. when i disconnect the wire to the S post, it ceases. Something isn't jiving. Was i supposed to remove the alarm entirely and replace with the gauge? i assumed both should be capable of being attached simultaneously. am i not connecting it to the correct signal wire? a little more advice pls. thx.

 

[sleepinin]

Re: Continuous Alarm on Merc 150 Saltwater

Look for the Tan wire with no blue stripe. It should not be connected to anything under your dash. Connect it to the post labeled "send" or "s" Leave the warning sender alone(tan/blue stripe). You have two sensors/senders on your engine. One for the alarm and one for the gauge, the tan/blue stripe wire appears to be your warning sensor.

 

[sleepinin]

Re: Continuous Alarm on Merc 150 Saltwater

joebiii,
This will be better for you in the future when you you have all these gauges installed but in the present you really need to address the overheat you experienced. The additional smoke you saw was likely steam that forms at about 212F and kinda confirms your overheat alarm. You need to change your waterpump and impellar, thermostats, and poppett. Better to never know what it was and to have fixed it than to burn up your engine. Order the parts and the service manuel and they'll all show up about the same time and you'll find they are all easy to do. Go to Mercurymarine.com then to parts express and enter your motors seriel number and you can view the part numbers and schematics. You can order the parts many places online including here at iboats or get them locally. I think you have to order the service manuel from mercury marine. Then the next time you have a problem the gauges will help you pinpoint it.

 

[ncfish1]

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!)

 

[sleepinin]

Re: Continuous Alarm on Merc 150 Saltwater

Alright, I'm confused. Sometimes I learn more from these post than the person asking the question. So let me clarify this and please correct me where I'm wrong because maybe the 2003 model has a different system than my 1999 or maybe I misunderstand the system. The high temp alarm sender will sound an alarm the minute it goes to ground. The temperature gauge sending unit is always grounded and the resistance to the current flow to ground is measured and gives the reading on the gauge. So if they were to share a wire the warning module would be grounded and would always sound the alarm. Also I would guess that the wire that joebiii followed(and connected to) that was not connected to anything is for an optional visual indicator "warning light".

 

[joebiii]

Re: Continuous Alarm on Merc 150 Saltwater

Alright, I'm confused. Sometimes I learn more from these post than the person asking the question. So let me clarify this and please correct me where I'm wrong because maybe the 2003 model has a different system than my 1999 or maybe I misunderstand the system. The high temp alarm sender will sound an alarm the minute it goes to ground. The temperature gauge sending unit is always grounded and the resistance to the current flow to ground is measured and gives the reading on the gauge. So if they were to share a wire the warning module would be grounded and would always sound the alarm. Also I would guess that the wire that joebiii followed(and connected to) that was not connected to anything is for an optional visual indicator "warning light".

the logic regarding the alarm with available optional warning light tail (bare end on the tan/blue wire) sounds like it may be accurate, and would explain why i've get the constant alarm with the gauge attached (because it's already grounded). I've had the boat out 3 times since my original/obscure problem. i was very low on oil, and filled my tank. don't know if i can write if off as trash in the inline water system or some mishap with the oil tank... or what. but i can tell you that i certainly don't leave home without a cell phone. as for the gauge, i would have much more comfort if i could get a reading on the temp. i tried connecting the gauge to the solid tan wire, and it didn't seem to do antying when i ran the engine. no alarm, but the temp didn't move either.

 

[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, that seems to make some sense too. i bet if i try it it will work.... but. The idea of the gauge + alarm sounds nice because it alerts your attention to look at the gauge. is there no way to have both without having to run a new wire from the sender?

 

[ncfish1]

Re: Continuous Alarm on Merc 150 Saltwater

If you want alarm and gauge, you'll need to install a sending unit in the blind holes located on the heads and leave the alarm circuit as is. This would require additional wiring (unless you find an unused wire from the engine),
If your alarm is sounding fairly immediately, then you are having sensor problems.
I simply got tired of hearing the alarm (false signals) constantly. With the gauge in front of you, you should notice problems when they happen.
Of every instrument I have, the temp. gauge is the one I keep an eye on the most. It helped me determine a problem I recently had simply based on what the temps. were doing and at what speeds.
Good luck with your problem.