# Alarm issues with a '91 Merc 90hp - Help please !



## jpollman (Jan 14, 2001)

The saga of the alarm "buzzer" continues. Well actually it's more of a high pitch squeal than a buzzer but buzzer is quicker and to the point. Back on the Musky opener in June I had an issue with this alarm going off after using the boat for about five hours trolling. I figured it was an overheat problem but also noticed that my volt meter was reading 16 volts and I was getting an occasional "High Voltage" message on my Humminbird fishfinder. So I pulled the boat out and took it home. I replaced the impeller and voltage regulator. I took it out this morning figuring everything would be OK. I launched at 6:00 from Harley and by the time I had taken the boat out beyond the mouth of the river and made my way over to the bay on the south side of the launch I already got another alarm and the darn high voltage warning again on the fish finder and it was reading at least 16V on the volt meter. This thing is driving me nuts! I shut the big motor off and used the trolling motor for about 45 minutes. After not doing any good I decided to fire up the big motor and see what would happen. Same story. With in just a few minutes I get this high pitched alarm and I don't know what it's trying to tell me. I had always assumed it was an overheat warning but that just can't be the case because I've got PLENTY of water coming out of the tell tale and the motor wasn't running long enough to overheat. I think I'm going to try to order an owners manual from Merc and see if I can find out just what this alarm is trying to tell me. But I wasn't far at all from the launch so at 7:30 I decided to pull the boat out and bring it home and bag the fishing for the day.  I'm really starting to get sick of this stuff. I seem to spend far more time WORKING on boats than I do ENJOYING them. I'm getting close to the point where I'm going to become boatless again and just fish off of other peoples boats again. 

Does anyone else have a motor of similar vintage that may have any ideas as to what it's trying to tell me?

I had a thought that maybe it IS an overheat warning but possibly just a bad sensor. Does that sound plausible.

Thanks in advance for any input.

Take care,

John


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## Mister ED (Apr 3, 2006)

John, I've been going through similar type nagging issues with my yamaha also. Finally resolved a carb issue, take a trip to the Bay, then have an over heat issue!! Even told the wife ..."now I remember why I sold the last boat!!". 

Anyhow, I am not sure with the Merc buzzer and why it alarms (other than temp) ... but as far as the temp goes ... it could also be the sensor or the thermostat. Both can be pulled and checked with hot water & a thermometer.

I'd think the buzzer is also tied into the oil level for the oil injetion ... just a thought.


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## roger23 (Jan 14, 2001)

John I had a early 90's 115 I went through a bunch of the same crap except for the voltage I finally replaced the alarm module I guess that was the problem.never got the alarm again before I replaced we took one off another motor to try it tired of being a parts changer Good luck


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## glockman55 (Mar 9, 2006)

I have a 95 Mariner 90hp, seems like an ongoing problem with Mercury( Mariner), low oil or over heating? Mine hasn't give me any trouble YET.:yikes: Let me know what you find out.

Thanks: Glock


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## jpollman (Jan 14, 2001)

glockman55 said:


> I have a 95 Mariner 90hp, seems like an ongoing problem with Mercury( Mariner), low oil or over heating? Mine hasn't give me any trouble YET.:yikes: Let me know what you find out.
> 
> Thanks: Glock


Will do Glock.

I looked at a service manual I have for it but it's a SELOC manual that covers all Merc motors for '90-'00 so it's hard for it to get specific on any one motor. The section on the warning systems state that on all oil injected motors there is a low oil warning. But there is also an overheat warning. The thing that blows my mind is that they appear to use the same signal. That's just STUPID! Why can't they have one tone for oil and another tone for overheat? It also states that there are two oil reservoirs. One mounted somewhere in the rear and one mounted on the power head. Well as far as I know, there is only ONE oil reservoir on my motor and it is definitely full. I just filled it up before I took it out so it shouldn't be a lack of oil problem. Maybe it's a heat sensor problem as I suspected. I'm gonna try to contact Merc and see about getting a service manual for my particular engine. That should make things much clearer and easier to trouble shoot.

I'll post what the solution is if I find one.

John


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## Mister ED (Apr 3, 2006)

John -

See if you can locate the temp sending unit. You should be able to pull it out and test it in hot water. Check the SELOC manual and it talks about checking the thermostat ... same technique for the heat sensor (at least on the Yamaha) but you need to use a continuity tester for it as well. In the SELOC Yamaha manual, it lists temps that the thermo switch sensor open and close (lists thermostat temps as well).

If you sort through things, it should also tell you how to check the oil sensor.

Another thought, if you can locate one or both of these sensors ... fire it up (get the waning to come on) and unplug one or the other sensor. I would think that unplugging one of them would cause the tone to go dead (do this only for troubleshooting ... LOL). This would at least point you in the right direction.

Yamaha manuals (both OEM and SELOC) talk about a remote oil tank as well. Only thing I can figure is that they are used more frequently in other areas of the country. On some other boards the guys from Texas and Fla, talk about their remote tank not transferring oil to the tank on the motor. I guess if you had a big enough gas tank ... you'd need more oil than the tank in the motor cowling would hold.

The SELOC manual for my Yamaha is a PIA also ... covers from 2-250hp, for a number of years. I also have the shop manual and it is good, as it only covers the mid-range engines (60,70,&90). However, once you find info in the SELOC, it does a little better job of explaining procedures ... for simple minded folk like me!! I like to use them both together.

Hope I helped.


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## Mister ED (Apr 3, 2006)

Just thought of a couple more things:

Make sure your inlet is not pulgged. AND ... are you certian you have the fins on the new impeller pointing the right direction??


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## double trouble (Nov 20, 2003)

my johnson does similar things when i troll a long time. i think it may be the oil reservoir sending that could be failing or is kinda shaky ,but i just squeeze the bulb once and it goes away for the rest of the day.i did clean the screen once and it helped a lot.at the bottom of the tank there is a filter screen. clean or replace it.try that first
if the motor is peeing a good stream of water and is not running hot ,you should be o.k. 

your voltage spike sounds like an entirely separate issue.their is probably a rectifier or a voltage regulator that is fried.that comes from running the motor with the battery cables not screwed down tight enough.previous owner neglect i would gather.try this site for more info.

http://www.boatpartstore.com/page16.asp


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## jpollman (Jan 14, 2001)

Thanks guys.

double trouble, I thought that I'd cured the high voltage situation by replacing the regulator. It's got a completely new one in there now. I just had a thought though. I just recently installed a tachometer. I think there must have originally been one in there but a previous owner removed it and installed an LCD fishfinder in its place. The tach is a simple three wire hookup with +/- power and a feed from the alternator. I couldn't find where the original leads were so I just supplied 12V from the other guages and ran a completely new wire back to the motor to the tach output. This problem with high voltage has cropped up since I did the tach install so maybe it's got something to do with that.

Instead of muffs I think I'm going to run the motor in a trash can full of water for a little while and see what that does. Then I can have the cowl off and it'll be a little easier to trouble shoot. I think I'm leaning toward more of a sensor problem than an actual overheat or lack of oil. As I said earlier the tank is full and that shouldn't be an issue so maybe the sensor is just bad. The first time I heard the warning today the motor had only been running for about six or seven minutes and there's plenty of water flow through the telltale. So I highly doubt that it was overheated at that point.

Aren't boats fun?   

John


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## glockman55 (Mar 9, 2006)

jpollman said:


> Will do Glock.
> 
> I looked at a service manual I have for it but it's a SELOC manual that covers all Merc motors for '90-'00 so it's hard for it to get specific on any one motor. The section on the warning systems state that on all oil injected motors there is a low oil warning. But there is also an overheat warning. The thing that blows my mind is that they appear to use the same signal. That's just STUPID! Why can't they have one tone for oil and another tone for overheat? It also states that there are two oil reservoirs. One mounted somewhere in the rear and one mounted on the power head. Well as far as I know, there is only ONE oil reservoir on my motor and it is definitely full. I just filled it up before I took it out so it shouldn't be a lack of oil problem. Maybe it's a heat sensor problem as I suspected. I'm gonna try to contact Merc and see about getting a service manual for my particular engine. That should make things much clearer and easier to trouble shoot.
> 
> ...


 
In my Manuel, it says The warning horn sounds continuously: The problem is engine overheat.
The warning horn sounds intermittent short beeps: The problem is low oil level in the oil injection system.
When the ignition key is initially turned on, the warning horn will sound (beep,beep) for a moment as a test to tell you the system is working. Failure of this test indicates a problem. NO SH#*. A simple oil light would have worked and a temp gauge too! I guess they could go bad too.


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## jpollman (Jan 14, 2001)

Man I'm getting sick of this!

In the last 3 weeks or so I've dropped at least $250 on this motor and I thought I'd be good to go for a while but this thing is driving me nuts. I still don't have a boat to use and as I said earlier, I'm just about to join the ranks of the boat less if it doesn't stop soon.

I just pulled the temperature sensor out and tested it. It appears to be working within a reasonable range. The SELOC manual I have has an error in it which I discovered so I called them and talked to a pretty helpful tech guy there. In the troubleshooting section it states that the switch should be CLOSED under normal circumstances and that when the temp reaches 162-178 degrees that it will open. Then the very next sentence says "the switch will reset back to a closed position when the temp reaches 182-198 degrees. I'm almost sure that they meant to say that the switch is normally OPEN and will close at 182-198 degrees. 
I took my switch out and got my multimeter wired up and checked it. I put the switch into a pot of warm water on the stove and started heating it. As the temp came up from the start the switch was open. When the temp hit 197 degrees the switch closed. At that point I turned off the heat and poured some cool water in the pot and slowly reduced the temp. When it hit 177 degrees the switch opened again. I did this procedure three times with similar results. (it closed and opened at the same temps or within a degree or two) That sure seems to be operating correctly but the guy at the Merc parts place couldn't give me the correct operating specs but just wanted to sell me a new switch. Gee big surprise, they go for $46 plus shipping! All in all that switch probably costs all of $3-$4 TOPS to produce!:rant: I'm not going to just dive bomb this thing with parts anymore either. I just spent $90 on a new voltage regulator and I've STILL got the same high voltage problem I had before. But according to the manual, anything over 16V is a problem but it's been reading 16V so maybe it isn't as much of a problem as I thought it was.

I just hate having all of that money tied up in a boat sitting in the driveway that I can't use because I'm afraid of getting on the lake and being a long way from the launch and having a problem and end up being stuck. I know that is always a concern but this darn latest intermittent problem is just about to push me over the edge.

OK, rant off.

I've gotta get back out there and see if I can figure out what the heck is wrong with this thing.

CYA later folks

John


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## tommytubular (Jan 25, 2002)

I didn't read the entire post.....but have you actually placed a voltmeter across the battery while its running and the alarm sounds? Is the voltage above 14.5 volts?

Secondly are the temperature and oil level measuring devices switches or sensors/senders?

The reason I ask is if the battery voltage goes up and they are sensors/senders, the reading across the sensors (be it a varible resistor or a thermister) will be affected proportionately and will send a inacurate signal (based on the increased battery voltage) to the alarm controller.

I do know that high battery voltage will affect your electronics as much if not more then low voltage


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## tommytubular (Jan 25, 2002)

I guess I should have read the post...

"I'm not going to just dive bomb this thing with parts anymore either. I just spent $90 on a new voltage regulator and I've STILL got the same high voltage problem I had before. But according to the manual, anything over 16V is a problem but it's been reading 16V so maybe it isn't as much of a problem as I thought it was."

Get out your own voltmeter and measure the battery voltage. Don't trust the gauge.

and if the battery voltage is 16 volts or higher...........it is a BIG problem!!

I would aslo bet the if the alarm controller senses 16 volts or a predetermined value over 14 volts....it will sound the alarm.....even though the book doesnt say it will.

For the record..........16 volts will cook your batteries at a minimum and is distructive on all your 12 volt accessories if high voltage is applied over time


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## jpollman (Jan 14, 2001)

Actually that's a good point. I hadn't thought about the high voltage affecting the sensors. But at this point I believe that the alarm I'm getting is telling me it's an overheat situation. (which I doubt is actually happening) But the sensor for the overheat warning alarm is just a temp sensor that is normally open. When the temp gets too high, it closes and closes the circuit setting off the alarm. I don't think that there is actually any voltage passing through that particular sensor. But maybe you're right. Maybe I should resolve the high voltage situation. If I figure that out, maybe the other problems will go away.

Thanks for the input! It sounds like it may lead me in the correct direction finally. 

John


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## tommytubular (Jan 25, 2002)

jpollman said:


> But maybe you're right. Maybe I should resolve the high voltage situation. If I figure that out, maybe the other problems will go away.
> 
> Thanks for the input! It sounds like it may lead me in the correct direction finally.
> 
> John



John, Id be willing to bet a cold one that I am right. 

As for why its over charging.........not all new voltage regulators are good (but it sounds like you replaced the old one with a new one and didn't fix the high voltage problem). This tells me that it is most likely something else. Look in your manual and see what they have for charging system diagnosis. Follow it to a T.


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## jpollman (Jan 14, 2001)

tommytubular said:


> John, Id be willing to bet a cold one that I am right.
> 
> As for why its over charging.........not all new voltage regulators are good (but it sounds like you replaced the old one with a new one and didn't fix the high voltage problem). This tells me that it is most likely something else. Look in your manual and see what they have for charging system diagnosis. Follow it to a T.


Thanks again Tommy!

I tell ya, if it does pan out and turns out to be the problem I owe ya more thad *A *cold one. You're getting a *twelve-pack*!

I'll keep ya posted. 

John


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## ozzgood2001 (Feb 15, 2003)

Now Now John you go this boat for a steal give it some slack. could be a simple cracked wire exposing the wirin shorting across something could be a loose plug could be a bad sensor could be could be.. your a caprenter just like me this is the fun stuff!! discovering problems and solving em!!


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## tommytubular (Jan 25, 2002)

John,

I live close, I have many years in the automotive business and mainly electrical systems, but I'm no marine mechanic. I'm going to PM you my number, call me if you get stumped and I'll swing by and see if we can figure it out.

Have volt meter......will travel


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## jpollman (Jan 14, 2001)

Thanks Tommy!

I tried to reply to your PM but your inbox is full. I've got your number and will give you a ring if I need a hand.

Thanks again,

John


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## tommytubular (Jan 25, 2002)

jpollman said:


> Thanks Tommy!
> 
> I tried to reply to your PM but your inbox is full. I've got your number and will give you a ring if I need a hand.
> 
> ...



PM's are cleared out.........

Any luck yet?


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## jpollman (Jan 14, 2001)

tommytubular said:


> Any luck yet?


No not really. 

I went out last evening and reinstalled the temp sensor. I then installed the muffs and fired it up. She ran fine. I hooked a brand new multimeter to the battery and let the motor run for about fifteen minutes. Varying the speed anywhere from about 1K to 2K rpms (2k for short 15 second or so bursts) and was reading 13.2-13.8V. Now one thing is that the water coming out of my hose is much colder than the lake water at this point. When I was out on Sunday I saw 79.8 degrees water temps on my fish finder. But I really don't think it's an overheat problem. I'm almost convinced that the bugaboo is this high voltage situation. I think I may take the boat over to Stoney and run it a little bit. It's much closer than LSC. That's the tough part about intermittent problems. They almost never show up when you're standing there with the test equipment to isolate them or have the tools to do something about it. :rant:

I'm willing to bet that as soon as I'm in the water and cruising around a bit the voltage problem will resurface. If and when it does, I'm going to put a multimeter on the battery directly and check to see how accurate the voltmeter in my dash is. But I feel like it's probably pretty close because I do get that high voltage warning on my Humminbird which is really a secondary indication of a problem. I don't want to be pushing 16v for long. 14.5 to 15V is tolerable but 16 is out of the comfort zone for me.

I'll post if and when I figure it out.

John


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## Gone Fishing (Jul 31, 2001)

John, this is a long shot but it happened to me on a outboard years ago. I got some weeds sucked into the intake and overheated the engine a bit. I cleared the weeds and everything looked alright. After that I would occasionally get an overheat alarm. Turns out that when I overheated the engine that one time, I melted a plastic sleeve that the therostat installed into. It melted it just enough to partially block the water passage. It wasn't completely blocked but it was enough to set off the alarm. Just a thought.


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## jpollman (Jan 14, 2001)

Thanks John,
at this point I'm willing to try ANYTHING. I'm gonna get back into this thing again this evening and see what I can find out.

John


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## oneadamseaol.com (Sep 3, 2018)

John, did you ever figure out the issue to this problem? Mine started doing the same thing yesterday. All the same symptoms and issues.


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## Copper44 (Sep 25, 2004)

Hey this post is 12 years old... you might be better off starting a new thread. But one thing is have you checked to see if the float is stuck in your oil resvoir? This will make your motor think it’s low on oil all the time.


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## Fld (Aug 7, 2018)

Copper44 said:


> Hey this post is 12 years old... you might be better off starting a new thread. But one thing is have you checked to see if the float is stuck in your oil resvoir? This will make your motor think it’s low on oil all the time.


it may be old but still no concussion??


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