93 Baja alarm buzzer won't stop going off

[ksstang]

Hello everyone. So I've ran in to a strange problem and about to go crazy trying to figure out this issue. I pulled my boat out this spring to get it ready to find out the guy that winterized it failed to do everything properly and it popped 3 freeze plugs. I finally got around to replacing those, fired it up the other night and knock on wood I think I escaped major damage. I found the oil to be 2qts low. When he changed the oil at winterization he only put 5qts in. I got the oil topped off to normal level, but now have the following issue. This is a Mercruiser 454 I'm dealing with.

So, on to my problem. Normally if you turn the key to the on position but don't start it within 7-10 seconds the alarm/buzzer will sound. As soon as you fire it the alarm should go off. Well, as soon as I fire it the alarm goes off, but within 3-5 seconds it comes right back on and constantly stays on while the motor is running and never goes off. My oil pressure is good on the gauge at 40psi. My water temp never gets over 150*. I checked my drive oil level and it's dead on.

I'm absolutely puzzled and stumped at what to check now. If anyone could be of some assistance it would be much appreciated. Thanks in advance.

 

[HT32BSX115]

Hello everyone. So I've ran in to a strange problem and about to go crazy trying to figure out this issue. I pulled my boat out this spring to get it ready to find out the guy that winterized it failed to do everything properly and it popped 3 freeze plugs. ...........

So, on to my problem. Normally if you turn the key to the on position but don't start it within 7-10 seconds the alarm/buzzer will sound. As soon as you fire it the alarm should go off. Well, as soon as I fire it the alarm goes off, but within 3-5 seconds it comes right back on and constantly stays on while the motor is running and never goes off. My oil pressure is good on the gauge at 40psi. My water temp never gets over 150*. I checked my drive oil level and it's dead on.

Howdy,

Welcome aboard!

Well, first of all, those are NOT "freeze plugs" They're called CORE plugs. It's sort of important because they are not there to protect against anything(especially freezing) . They're there to plug holes left in the block due to the sand casting process.

It also just so happens that they "pop" out when water left in the block during freezing temps, freezes. So I guess you could call them "Freeze DAMAGE plugs" ......You'll find out soon enough.

It would help if you post your serial number/year model. Mercury made a fair amount of changes in those engines depending on if it's older or newer. The alarm system is generally a single wire connected to a buzzer. The other wire is connected to 14V +.

Ground that single wire (not the + wire) and the buzzer sounds. The oil pressure, temp and drive lube monitor sensors will ground if they are in "alarm" so any one of those sensors will ground the same wire.

Also, if the wire has chaffed against a metal item anyplace, (that's also grounded) it doesn't take much to short the wire and ground it.

Any of the sensors could be erroneously grounding the wire too......... just disconnect them one at a time to determine which one it is. If you get all three disconnected and the buzzer still sounds, the wire may be rubbing somewhere that has worn through the insulation.

Regards,


Rick

ALSO...........DO YOUR WINTERIZATION next winter. it's not all that hard!!!!

 

[ksstang]

I did a little diagnosing with my volt meter. The wire feeding the buzzer has continuity on it all the time. I pulled it loose where it was connecting to the switch and tested it. The single wire coming out of the buzzer that runs all the way back to the oil pressure alarm sensor has continuity on it all the time. I would think that wire should be normally open until something activates it.

 

[Fun Times]

Hi there, welcome to iboats!

Is your engine carbureted or MPI?

If it's carbureted then you could try disconnecting the Temp, Oil & Drive Oil Reservoir wires one at a time to see if the horn will stop, that should help give you a direction to start with of what could be bad if any. The color of the wires to the temp, oil & drive lube reservoir should be a Tan/Blue....Some had just a tan wire though. If your engine model is an MPI, then there may be additional sensors that could sound the alarm. Keep in mind that the sensors you see at the gauges is not necessarily the same sensors/locations that's sounding the horn.

Early production and service ECMs had the following items that will sound the alarm;
1. MCM/MIE ? Horn will sound if there is an active engine Diagnostic Trouble Code [DTC] that is occurring while the engine is running. The horn will not sound a stored DTC. Correcting the DTC malfunction will stop the horn.
2. MCM/MIE ? Horn will sound if the battery voltage to the ECM is low, [less than 9v for at least 5 seconds]. Using the throttle lever to increase engine rpm to get the alternator to put out more voltage will correct most low voltage problems.

 

[ksstang]

Thanks! Mine is Carb'd. I disconnected the oil with it running and the alarm still sounded, following the water and it still sounded, but haven't done the reservoir one yet. I just find it funny that it wasn't doing this the last time the boat was out last year, and now just all of a sudden it does it the first startup.

I also find it funny that the wire coming off the buzzer all the way back to the oil sensor has continuity on it all the time. I pulled it loose from the sensor and tested the wire to ground and the volt meter beeped at me.

 

[ksstang]

Does anyone know on both the oil and water sensors whether they should be normally open or normally closed? When I go from the sensor to ground with my volt meter on ohms should I beep on the meter or not?

 

[HT32BSX115]

Does anyone know on both the oil and water sensors whether they should be normally open or normally closed? When I go from the sensor to ground with my volt meter on ohms should I beep on the meter or not?

The oil (LOW) and water temp (HIGH) are always open when "normal" I.E. normal oil pressure----> "open" Normal temp ---> open.

Drive lube monitor----> NOT-LOW "open"

If any of them are CLOSED. Disconnecting each, removes that one from the circuit.

 

[ksstang]

I disconnected each one with the motor running, starting with the water and the buzzer stayed on. I then did oil and it stayed on. Disconnected the drive bottle and the engine died.

 

[Bt Doctur]

Disconnected the drive bottle and the engine died.

Nope, dosent work like that

 

[ksstang]

Well, I tried that reservoir bottle for my out drive fluid twice and each time I pulled the wire loose it killed the motor.

 

[Bondo]

Well, I tried that reservoir bottle for my out drive fluid twice and each time I pulled the wire loose it killed the motor.

Ayuh,.... That ain't how it's supposed to work, so I'd say ya got some wires crossed, or shorted together, Somewhere,...

 

[ksstang]

Got it figured out. It's the reservoir bottle sensor for the drive. When I unplugged it and it died it was the negative side of that switch. I unplugged the tan/blue wire from that sensor and the buzzer shut off. The bottle is full of fluid too.

 

[HT32BSX115]

Looks like you'll be replacing that switch.

It should only sound the alarm. It shouldn't be killing the engine

 

[ksstang]

Looks like I'll be replacing the whole reservoir bottle. They don't sell just the sensor unfortunately. At least I can't find just it by its self.

 

[HT32BSX115]

Looks like I'll be replacing the whole reservoir bottle. They don't sell just the sensor unfortunately. At least I can't find just it by its self.

Yeah. I don't think they do either. Found a couple of them on eBAY for about $40 or so. Well worth it!