1989 90HP Mariner

[Briseno09]

Hello, I am having an issue with the warning module. I bought a boat with this outboard about 2 years ago now and ever since I have had it, the warning buzzer has been on as soon as i turn the ignition switch on. A mechanic checked it out after I purchased it and said the buzzer itself was bad. I bought a new one and replaced it(connects to the ignition switch) and it's still on, constantly, never turns off. I found a service manual for the outboard online and got to troubleshooting. Ended up believing it was the temp sensor. So i bought a new one for about 100 bucks, connected it and the buzzer is still on. It turns off as soon as i disconnect the black wire, which i am assuming is ground(manual says if it turns off after disconnecting the black wire, it is a bad temp sensor but i just put a brand new temp sensor in and haven't used the boat since swapping the temp sensor??) I went a step further, disconnected the two blue wires from the warning module, re connected the black wire and the buzzer came back on. I am not sure if the warning module itself and wouldn't know how to test it.

The serial number to the outboard is: 0D121478

And the service manual can be found here:

Mariner 90 Service Manual.pdf

drive.google.com

The section containing information regarding the warning module can be found on page 124 w/ the wiring diagrams being on 124. Mine is the model without the test button. Perhaps, I'm not reading the manual correctly, but I am not sure what to do here.

Thanks for any information you can provide.

 

[Briseno09]

Update, If i completely disconnect the temperature sensor(disconnected the single lead from the temp sensor from the terminal block it was connected to), the warning horn still sounds

 

[Briseno09]

Not sure how it's supposed to work, but seems like the signal is coming from the warning module itself or the engine harness.

 

[Sea Rider]

That's a fresh or saltwater 32 year oldie motor ? Are the Thermostat and Poppet Valve and their respective housings in impeccable clean working conditions ?

Happy Boating​

 

[QBhoy]

Do you have an oil injection tank on the engine ?

 

[Briseno09]

That's a fresh or saltwater 32 year oldie motor ? Are the Thermostat and Poppet Valve and their respective housings in impeccable clean working conditions ?

Happy Boating​

To be honest, I don't know what if it's a model for salt or fresh. I do know the previous owner used it in saltwater and I've used it in saltwater with rinsing the internals by running the engine with freshwater. I have no idea about the thermostat. Will a stuck thermostat cause the heat temp sensor to open the circuit? Or is something connected to the wiring harness that gets signal/readings from the thermostat that is causing the warning module to throw the beeping noise?

 

[Briseno09]

Do you have an oil injection tank on the engine ?

Yes it has a tank on the engine and two blue wires going from the warning module to a sensor in the tank. If I disconnect the two blue wires, but leave the temp sensor connected, the noise doesn't stop. It seems like no matter what is connected to the module, it beeps as soon as I connect the black wire, which I'm assuming is ground

 

[Sea Rider]

To be honest, I don't know what if it's a model for salt or fresh. I do know the previous owner used it in saltwater and I've used it in saltwater with rinsing the internals by running the engine with freshwater. I have no idea about the thermostat. Will a stuck thermostat cause the heat temp sensor to open the circuit?

Flushing any salt water used motor for that long years for as long as you want is no indicative that will be removing salt build-ups on the entire water passages, and that's from long plain experience running and tearing salt water motors. When buying second hand motors it's a Must check the Temp Sensor, Thermostat and Poppet Valve working conditions and their internal housings, clean, replace whichever needs to be done for the motor to cool and run right.

A stuck thermostat, Poppet Valve giving poor cooling issues will warn the Temp Sensor to trigger the overheat buzzer alarm while boating specially at high rpm. Have seen a similar case to yours in which all the 3 mentioned parts were doing their homework right and the CDI was found being the culprit...

Happy Boating​

 

[Briseno09]

Flushing any salt water used motor for that long years for as long as you want is no indicative that will be removing salt build-ups on the entire water passages, and that's from long plain experience running and tearing salt water motors. When buying second hand motors it's a Must check the Temp Sensor, Thermostat and Poppet Valve working conditions and their internal housings, clean, replace whichever needs to be done for the motor to cool and run right.

A stuck thermostat, Poppet Valve giving poor cooling issues will warn the Temp Sensor to trigger the overheat buzzer alarm while boating specially at high rpm. Have seen a similar case to yours in which all the 3 mentioned parts were doing their homework right and the CDI was found being the culprit...

Happy Boating​

Thanks for that info and I'm sure a flush won't get all of the salt out. I'll pull out the thermostat and poppet valve when I get home. I'm going to swap that out regardless of the warning module issue. I guess my final question is, if the t stat and/or the poppet valve are bad, would that cause the warning module to sound even when the engine is off/haven't been turned on in weeks? As soon as the ignition is on, it sounds

 

[QBhoy]

Yes it has a tank on the engine and two blue wires going from the warning module to a sensor in the tank. If I disconnect the two blue wires, but leave the temp sensor connected, the noise doesn't stop. It seems like no matter what is connected to the module, it beeps as soon as I connect the black wire, which I'm assuming is groun

Is the tank with oil or level sensor could be at fault

 

[Sea Rider]

I guess my final question is, if the t stat and/or the poppet valve are bad, would that cause the warning module to sound even when the engine is off/haven't been turned on in weeks? As soon as the ignition is on, it sounds

Nope a cold motor will not trigger the buzzer, only when the motor has run for a while and the temp sensor has detected an overheat going on on the powerhead will trigger the buzzer alarm, no way with motor OFF. Out of curiosity, post Thermo, Popet Valve and both internal housings condition to know how much salt layers, crusts amounts has been collected over the years boating in salt water. Check the oil tank's oil level as suggested, Good Luck!!

Happy Boating​

 

[Texasmark]

The warning system generates a ground for a horn which is energized by 12v from the key ignition switch being in any position but OFF if there is a temperature or oil level problem.

Some engines have a modulation module so that low oil generates a warbled tone to distinguish it from the over heat alarm.....low oil can be tolerated for awhile allowing you to motor back to the dock as oil is still in the tank whereas over temp is a stop running the engine when it sounds.....

With what you said, I see one of 3 conditions:

1. Wiring harness wire (Tan color in post '96 Mercury engines) shorted to ground somewhere....a chafe point.
2. Overtemp sensor embedded in the water jacket cover (spark plugs stick through it) on the rear of the block shorted out....remove the screw, pull it out and with it in the air if the horn quits it's shorted....if the horn still blows see #3.
3. You have an optional module in your engine and its shorted. Disconnect the connector to it and the horn should stop blowing.

 

[Briseno09]

Nope a cold motor will not trigger the buzzer, only when the motor has run for a while and the temp sensor has detected an overheat going on on the powerhead will trigger the buzzer alarm, no way with motor OFF. Out of curiosity, post Thermo, Popet Valve and both internal housings condition to know how much salt layers, crusts amounts has been collected over the years boating in salt water. Check the oil tank's oil level as suggested, Good Luck!!

Happy Boating​

For the sake of curiosity and informing others, I'll post pictures of how it looks haha I did take it out yesterday and cleaned off the tstat a bit. I'm picking one up today and swapping it so when I do that I'll get some pics and post them. Thank you for your responses

The warning system generates a ground for a horn which is energized by 12v from the key ignition switch being in any position but OFF if there is a temperature or oil level problem.

Some engines have a modulation module so that low oil generates a warbled tone to distinguish it from the over heat alarm.....low oil can be tolerated for awhile allowing you to motor back to the dock as oil is still in the tank whereas over temp is a stop running the engine when it sounds.....

With what you said, I see one of 3 conditions:

1. Wiring harness wire (Tan color in post '96 Mercury engines) shorted to ground somewhere....a chafe point.
2. Overtemp sensor embedded in the water jacket cover (spark plugs stick through it) on the rear of the block shorted out....remove the screw, pull it out and with it in the air if the horn quits it's shorted....if the horn still blows see #3.
3. You have an optional module in your engine and its shorted. Disconnect the connector to it and the horn should stop blowing.

Thanks! Seems more to me that it's a wiring issue or a bad module. As soon as I connect the lead from the engine harness to the module, it sounds the buzzer. I'll continue to bypass it. I was hoping I could get it fixed, but seems that I'll either be wire chasing or shelling out some more cash to get it working. Thank you!

 

[flyingscott]

Look in the oil tank. those motor are notorious for the magnet falling off and setting off the alarm.

 

[QBhoy]

Defo need to look at the oil tank sensor. Said it earlier too. Didn’t see mention that you did. Good luck.

 

[flyingscott]

And get a big garbage can and some salt away to try and clear the passages. Take any thermostats and poppet valves out when you do it.

 

[Dukedog]

do you have a small plastic term block mounted on tha block with three wires on it?.. are they a tan/blue tracer, tan, and a black?

tan/blue goes in tha harness to tha front of tha boat..
black goes to tha over temp sensor..
tan goes to tha oiler module..
disconnect one at a time and check for an alarm.