1991 Mercury 200 HP BEEP BEEP BEEP

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
floater
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1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Fri Jun 12, 2020 5:33 am

My 1991 Mercury 200-HP engine has been setting off a BEEP BEEP BEEP aural alert. I've have been throwing parts at [the engine hoping to fix the BEEP BEEP BEEP aural alert]. Here is what has been done:
  • I changed out the two thermostats and the impeller as a precaution.
  • There are no blockages in the oil lines and no leaks.
  • I've primed the oil pump and evacuated any air bubbles.
  • I removed the oil pump and turned the powerhead by hand and the long metal driven gear shaft turns like it should indicating the plastic drive gear on the crank is still in good shape.
  • Oil comes to the inlet side of the oil pump but no oil seems to come out of the outlet side with the motor idling.
  • I've disconnected the oil warning module and I still get the BEEP BEEP BEEP.
  • I have a new oil pump shaft sensor coming next week in the hope it will stop the BEEP BEEP BEEP
I am at a loss now. Give me more ideas [for how to stop the BEEP BEEP BEEP].

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sat Jun 13, 2020 5:03 pm

FIrst, congratulations on keeping that 29-year-old two-stroke-power-cycle V6 engine running. We used to get many posts about a Mercury engine with a BEEP BEEP BEEP problem, but it has been years since anyone asked about this.

For my suggestions about what to investigate, read my reproduction in HTML of the

Mercury Automatic Oil-Gasoline Mixing System
http://continuouswave.com/whaler/refere ... ction.html

Read my comments which explain the causes of the BEEP BEEP BEEP in my article in the thread at

Mercury 1996 Outboard: Chronic BEEP-BEEP-BEEP
http://continuouswave.com/ubb/Forum3/HTML/010626.html

Read an account of a solution to the BEEP BEEP BEEP problem that turned out to involve a very unlikely component, the actual wiring harness:

1988 Mercury Black Max 150 XR4 BEEP BEEP BEEP, Cuts Out
http://continuouswave.com/ubb/Forum3/HTML/015013.html

WIthout any sort of annunciator lamps to indicate the cause, a simple aural alert alarm as used on the obsolete and out-of-production Mercury engines demands that the operator be able to interpret the cadence of the aural alert and the situations in which the aural alert occurs in order to make a guess about the which component or sensor is causing the aural alert.

In any alarm system when an alarm occurs there are three possible situations:

  1. the alarm system is working perfectly, it has detected a problem, and the repair action is to fix the problem
  2. the alarm system is working but has a faulty sensor, the faulty sensor is indicating a problem where none exists, and the repair is to replace the sensor;
  3. the engine is working properly, the alarm sensors are working properly, but the alarm system itself has a defect that is causing the false alarm, and the repair is to replace the faulty component in the alarm system.

The sensors are external to the alarm system and can be tested by disconnecting them from the alarm system.

The alarm system consists of a central module that receives sensor input, and an aural alert sounder that produces the aural alert sound. Either could be defective.

While attempting to diagnose the problem, run the engine on a pre-mix of gasoline-oil so no damage will occur if the actual problem is related to loss of automatic oil mixing with the gasoline fuel.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sat Jun 13, 2020 5:07 pm

floater wrote:...I've disconnected the oil warning module...


Please identify the components according to the nomenclature used by Mercury in the diagram labeled OIL [MIXING SYSTEM] COMPONENTS. Are you trying to describe CALLOUT 9, MOTION SENSOR?

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Sat Jun 13, 2020 5:26 pm

[The component I was calling the "oil warning module" is shown on the Mercury OEM service manual] diagram as CALLOUT 10 "electrical sensor." On a Mercury parts catalogue it's also called a "Warning Module Assembly."

I first disconnected the motion sensor CALLOUT 9 on [the Mercury OEM service manual] diagram, to see if that circuit change would silence the alarm. This didn't work so I disconnected all the wires running connecting to the Warning Module Assembly; that didn't silence the alarm either.

I've read elsewhere that you have to disconnect the power leads to this warning module to get it to silence. What baffles me the most is that the pump gear and the shaft inside the motor do turn with the powerhead. The lack out outflow oil maybe due to running it only at idle on the muffs and hose. I will be removing the pump and running it on muffs again while spinning the pump with a drill to see if any oil comes out of the outlet side to make sure the pump is actually pumping.

I have lots of parts on the way from the Dealership. If all else fails to silence this alarm and assure me that the motor is getting oil I will simply disconnect the pump and put in the delete kit and start mixing my oil and gas by hand. Thanks the tips

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sun Jun 14, 2020 4:24 pm

floater wrote:[The component I was calling the "oil warning module" is shown on the Mercury OEM service manual] diagram as CALLOUT 10 "electrical sensor." On a Mercury parts catalogue it's also called a "Warning Module Assembly."


The nomenclature "Warming Module Assembly" is better and more descriptive. As I mentioned in my assessment of the alarm system, it is entirely possible that the engine is working properly, all sensors are working properly, and the cause of the BEEP BEEP BEEP alarm is due to a failure in the alarm module (AKA "Warming Module Assembly" AKA "electrical sensor") itself.

ASIDE: the electrical and electronic components in Mercury outboard engines of that production epoch are somewhat infamous for limited lifespan. In this case, 29-years is quite a reasonable service life for an electronic component, particularly one that was not exactly built originally to lunar mission spacecraft standards, was made in Mexico, and was probably designed at least a decade or two prior to 1990 using analog circuitry involving capacitors. Capacitors are component know to change value with age, particularly inexpensive low-grade capacitors.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sun Jun 14, 2020 4:41 pm

I recall somewhat that the MOTION SENSOR operates in this manner:

  • an electrical sensor connected mechanically to the oil pump in some unknown manner detects motion in the pump; the motion detected is some sort of rotary motion of the pump input drive shaft. and not a fluid of the oil being expelled from the pump
  • the electrical signal is in direct proportion to the engine speed; this signal from the motion sensor connects to the alarm module
  • an electrical signal originating from the "switch box" (which is Mercury's somewhat unusual name for an electrical module that controls the primary current to spark ignition high-voltage coils) is also connected to the alarm module; this signal also varies in proportion to the engine speed
  • the function performed by the alarm module is to continually compare the two signals that are directly proportional to engine speed, and to generate an alarm signal if the two signals no longer are in proportion to each other; here I assume that the nature of the signals are alternating current signals, not a continuous signal, and the parameter being compared is the frequency of the alternating signals, again in some unknown manner that is able to reliably detect when there is a direct portionality between those frequencies as the normal state and when the frequencies are no longer in direct proportion to each other, the state is considered abnormal and worthy of an alarm.

Assuming my inference about how the alarm module works with the the signals from the motion sensor and the switch box, I do NOT believe that you can test the function of the motion sensor on the oil pump with regard to whether or not it is causing an alarm condition by simply disconnecting its wired connections to the alarm module. If no signal at all is provided from the motion sensor, the inference is that condition WOULD CAUSE an alarm.

The problem here is you (and I) are investigating with backwards logic, that is, there is a constant alarm and we are trying to deduce what is causing it. It would be more straightforward to test sensors input to see if they could cause an alarm by simulating their alarm signals.

My further inference is that the sensor for OVERHEAT is probably a simple electrical switch that operates with a normally-open condition, but if the temperature exceeds the switch threshold, the switch closes. This is a very simple sensor to test. If the engine is stone cold the sensor can be disconnected and its resistance checked. The resistance to ground when the engine is cold should be infinitely high--no continuity.

Another sensor input is the FLOAT SWITCH in the oil reservoir. [See below in a follow up post for details on how the float switch works.]

There are two possible problems that can cause a false alarm in the oil level portion of the circuit: the floatation collar on the switch become saturated with oil and lose its buoyancy and not rise with the oil level or some other mechanical problem with the float and its magnet occurs; or the switch is being properly actuated mechanically by the float mechanism but the switch has failed and remains in the alarm position. See a follow-up post below for more information on the float switch operation.

Returning to the oil pump motion sensor, because the alarm module is presumed to operate by comparing the signal from the oil pump motion sensor to the signal from the switch box, it seems reasonable to conclude that loss of either signal would produce an ALARM condition. Exactly what outcome would result from loss of BOTH signals is unknown to me. I cannot predict with any certainty that your test procedure of disconnecting both the motion sensor input wires (WHITE, BLUE-WHITE, BLACK) and the switch box input wire (GREEN) is a valid way to simulate an NORMAL condition that would stop the BEEP BEEP BEEP. It seems just as reasonable to presume that your test method simulates the ALARM condition. WIth that in mind, I don't know if your test has proven that the alarm module AKA "electrical sensor" AKA "Warning Module Assembly" is faulty.

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Sun Jun 14, 2020 6:51 pm

Thanks for the detailed input.

The oil drive shaft has a sleeve on it that connects to the oil pump. This sleeve has a small black magnetic circle on it. It is from this magnet that the signal of the spinning shaft is picked up by the motion sensor.

I removed the oil pump today and spun it with a drill. On high speed the discharge line of the oil pump started to drip drip drip like it was trying to push oil into the fuel pump. I wasn't a constant flow but just a steady drip.

I disconnect the purple [VIOLET] wire that powers the Alarm Module and the beeping went away.

I ran the motor with a 50:1 gas oil mix and let it idle for ten minutes and the powerhead temps didn't go above 125 degrees.

I have a new temperature sensor and oil motion sensor on the way this week. I will post back if either or these silences the alarm system.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sun Jun 14, 2020 11:52 pm

floater wrote:I disconnect the [violet] wire that powers the Alarm Module and the beeping went away.


That is not a fair test. With no power available, the electronic aural alert sounder can't possibly work.

I look forward to finding out what some more new parts will do to fix the alarm and possibly fix the problem causing the alarm, too.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Mon Jun 15, 2020 8:50 am

FLOATER--when you get some more new parts for the Mercury 1991 200-HP engine in your efforts to determine the cause of the BEEP BEEP BEEP alarm and to remedy the problem, I suggest you don't install all the new parts at the same time.

Install the new replacement parts one at a time, and then test to see if the BEEP BEEP BEEP constant aural alert or warning horn is silenced. In this way we can learn which new component cured the problem.

Also, assuming you do finally remedy this problem and silence the BEEP BEEP BEEP, I would like to ask you do go back and do some checking on the normal status of the two switches that connect to the alarm module in order to determine if the normal status for the switch is to be closed or open. The two switches are the engine temperature switch and the oil reservoir float switch. It would be VERY HELPFUL to know the actual configuration of those switches.

If the normal configuration of the engine temperature switch and the oil reservoir float level switch were known, then in the future diagnosis of problems related to the BEEP BEEP BEEP problem could be more simply made. A simple resistance check of the two switches would be able to eliminate them as a cause of the BEEP BEEP BEEP problem.

I would like to get to the bottom of this famous BEEP BEEP BEEP problem and be able to offer better advice on diagnosis of its cause. This BEEP BEEP BEEP problem with Mercury oil-mixing engines has been a very common topic for the past 20-years.

IMPORTANT NOTE
Regarding the amount of oil flow from the oil pump, there is a mechanical linkage to the pump from the throttle cable. I infer that the purpose of this linkage is to increase the rate of oil output from the pump per revolution when the throttle lever is moved to higher settings. In this way when the engine runs at idle speeds, the oil output from the pump is low, producing a minimal mixing of fuel and oil. Correspondingly, when the throttle lever is moved to higher throttle settings, the oil output of the pump per revolution increases, producing a richer mixing of oil into the fuel as necessary for cylinder lubrication at higher engine speeds. On that basis, you might want to operate the throttle lever linkage on the pump while testing it using a drill to rotate the input shaft; you should see more oil output when the throttle lever linkage is moved toward full-throttle.

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Mon Jun 15, 2020 9:55 am

Great idea on the oil linkage. I will attempt that tonight. I am planning on swapping out the new temperature switch first as it's the cheapest at 58 bucks. If that doesn't help I will put in the oil pump shaft motion sensor at 156 bucks! I neither of these help I will disconnect the oil system for now and just mix oil and gas. The cost of the warning module is 460 dollars up here in Canada. I will try and find a used one that works and try that at a later date. If you know how to test the two switches you mentioned can you explain a simple method too me? I have a digital volt meter but i'm still not too confident with it. Thanks

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Aside on how a switch works and how to test a switch with an Ohmmeter

Postby jimh » Mon Jun 15, 2020 12:14 pm

A simple SPST switch has just two states: open or closed.

When the switch is closed the resistance between the switch terminals will be very low, less than 1-Ohm.

When the switch is open the resistance between the switch terminals will be very high, millions of Ohms or infinite Ohms.

To measure resistance the circuit element--the switch in this case--must not be connected into the circuit. The measurement of resistance is accomplished by the measuring device sending a small current through the circuit element being measured. Therefore there cannot be any other source of current, as would occur if the device is left connected to other circuitry.

If you need a tutorial on how to use an Ohmmeter, you can see some examples of the method here:


https://www.fluke.com/en-us/learn/best- ... resistance

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby Phil T » Mon Jun 15, 2020 1:43 pm

I think it may be time to talk to a Mercury Parts desk at a dealership. Better yet, spend the $150 for an hour of diagnosis time from a certified Mercury technician.
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floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Mon Jun 15, 2020 9:04 pm

I took off the oil pump again and spun it with a drill while holding the [lever linked to the throttle] in the full throttle position. No oil came out the outlet side at all.

Q: does the onboard oil tank, mounted to the motor, actually need to have pressure in it to get the oil to flow to the pump?

If not, then I believe the oil pump may be the [actual cause of] the alarm going off.

As I've mentioned before, the plastic drive gear turns the input shaft while I turn the power head by hand and this in turn turns the sleeve with the magnetic circle on it that would be picked up by the motion sensor.

[I am now] back to maybe the pump has failed but the motion sensor is still detecting the shaft as spinning.

The BEEP BEEP BEEP alarm would then be due to an overheat condition.

I've already changed the impeller and two thermostats with new ones. With the possible lack of oil and running on the hose and muffs I may not be producing enough water pressure to cool the engine properly.

I will put the boat in the water this week and see if submersion helps cool the engine to the point the alarm goes off. I will also pick up a pump on ebay and see if this helps.

I tested the oil [float switch] on the [under-cowling] oil tank. With the float in its bottom position, showing a drop in tank level of oil, [the resistance between the switch terminals was] 0.002 ohms. With the float up at the top near the cap, showing a full tank, the [resistance measured] went to open circuit. Seems to me the [float switch] is working as it should.

I will test the temperature sensor tomorrow and post back.

At this point I would also like to just toss in a used working warning module just to see if that may be the [cause of the alarm].

I will not go to a dealership for [diagnosis and repair of the BEEP BEEP BEEP] as I know what they will say' "Just disconnect [the automatic oil mixing system."

I want to fix this problem myself so i can learn something along the way.

Moderator's note: I have moved several comments to this thread from a wanted-to-buy post in MARKETPLACE. The MARKETPLACE forum is not for discussions, it is just for notices of for-sale or wanted-to-buy. Please use this thread in REPAIRS and MODIFICATIONS for all comments regarding the repair of this problem--jimh]

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 8:47 am

floater wrote:Q: does the onboard oil tank, mounted to the motor, actually need to have pressure in it to get the oil to flow to the pump?


Interesting question. In the pictorial diagram in the Mercury literature, the under-cowling oil reservoir is drawn as being located higher than the oil pump, and on that basis the flow of oil into the pump from the under-cowling reservoir would be from gravity.

Note that there is a 2-PSI check valve (CALLOUT 5) whose purpose is to prevent a vacuum from forming in the under-cowling reservoir and stopping oil flow by gravity in the event of loss of oil supply from the remote tank. Mercury notes the engine can run for 30-minutes after the remote oil tank oil level drops to empty, i.e., there is no flow from the remote tank.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Tue Jun 16, 2020 10:00 am

I replaced that check valve last season with a new one. I read that I should pre-mix a portable boat fuel tank with gasoline and oil at a ratio of 50:1 and run the engine on the lake. If I put a mark on the oil tank and the level goes down I can ascertain if the oil pump is actually working. I will try this later this week and report back.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby biggiefl » Tue Jun 16, 2020 10:02 am

A faulty oil pump or overheat condition would indicated by a constant BEEEEEP, not a BEEP BEEP BEEP. A constant BEEEEP means stop; Houston, we have a problem.
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 11:42 am

You should monitor the REMOTE oil tank to observe a change in level. The under-cowling tank level should not change.

I very much doubt that the alarm is being created by an overheat condition that was caused by lack of oil. If there were no oil, the engine would probably have a catastrophic failure in a cylinder before the engine block temperature became so high it set a warning alarm.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 11:45 am

biggiefl wrote:A faulty oil pump or overheat condition would indicated by a constant BEEEEEP, not a BEEP BEEP BEEP. A constant BEEEEP means stop; Houston, we have a problem.


NICK--I think you are correct on that distinction in the cadence of the alarm. But can you give a reference that confirms that?

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 11:57 am

floater wrote:I tested the oil [float switch] on the[under-cowling] oil tank With the float in its bottom position, showing a drop in tank level of oil, [the resistance between the switch terminals was] 0.002 ohms. With the float up at the top near the cap, showing a full tank, the [resistance measured] went to open circuit. Seems to me the [float switch] is working as it should.


Thanks for that information on the behavior of the float switch in the under-cowling oil tank. Now we know that the switch configuration is NORMALLY CLOSED, which will occur when the oil tank level is low, and the switch must be raised to a higher float level to become OPEN. This means the behavior of the alarm system is to sound an alarm when the oil float switch is closed.

With this information, a simple test to see if the cause of the BEEP BEEP BEEP alarm is from the oil float switch is to disconnect the switch from the alarm module, simulating the condition of an oil tank level that is above alarm threshold. The alarm should stop.

If the BEEP BEEP BEEP continues when the oil tank float switch has been disconnected, then the switch was not the cause of the alarm. Some other component must be causing the alarm.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 12:05 pm

In my reply to your questions, I pointed you to a separate article I had written which contained concise information. I am not sure if you read that article, so I am going to re-post it here:

    My first recommendation is that you immediately switch over to a fuel using pre-mixed oil and gasoline at a ratio of 1:50 until you solve this problem. This will save you from destroying your motor by running it without oil while looking for the cause of the alarm.

    The owner's manual of almost every outboard will contain information about how to interpret alarm signals. I do not have the owner's manual for your outboard.

    In general I have found that the literature published by Mercury about their outboard motors is quite good, and it will explain in detail how your motor works and how to interpret any alarm conditions it gives you.

    If your Mercury outboard has an alarm system which is similar to the one described for a c.1989 motor, you can read about it in the Reference section. See:

    http://continuouswave.com/whaler/refere ... ction.html

    For the moment, we proceed on that assumption.

    The alarm module is somewhat limited in its ability to pass information to the owner. It only has an aural signal. It modulates the cadence of the aural signal to indicate the function. There are only three possible cadences.

    When the key is turned from OFF to ON, the alarm sounds a signal to verify that it is operating properly. This signal sounds like a Morse code letter D or B, i.e., "dah-didit" or "dah-dididit". If the module does not sound this signal it is malfunctioning.

    After engine start, the alarm goes silent until there is an alarm condition.

    If the engine temperature rises above the threshold of the thermal switch in the cylinder head, the switch closes. This causes a continuous BEEEEEEEEP tone alarm which persists until the temperature falls enough for the switch to open. This ends the alarm tone.

    Any of the following conditions will signal a BEEP-BEEP-BEEP:

    --oil level below the float switch level in the under-cowling reservoir

    --input gear shaft to mixing pump turning too slow in relation to engine speed

    There is no way to tell which of these events causes an alarm. You have to deduce which is the problem by inspecting the motor.

    It is also possible that any of the following conditions will also signal a BEEP-BEEP-BEEP:

    --defective float switch in the under cowling reservoir

    --defective motion sensor in the mixing pump

    --defective ignition module sending false signal

    --defective alarm module creating false signal

    If you want to diagnose this problem further, you will need to obtain the service manual for you engine. Thoroughly read the service manual. It will cover the oiling system and alarm system in detail. There are many complex interactions which can cause these alarms.

    For example, there are seven different situations which can cause the level in the engine reservoir tank to be low.

    The first place to start with diagnosis is at the alarm module.

    Does the alarm beep the proper cadence when you turn the key from OFF to ON?

    Problems with these Mercury alarm modules seem to be very common. Let's see if we can resolve your Mercury motor malfunction.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Tue Jun 16, 2020 12:13 pm

I have the service manual for this Mercury motor. I have read and re-read it several times now.

My alarm is a constant BEEP BEEP BEEP but it sounds like it is breaking up like [there is] interference in the beep sound or the speaker surface itself may be cracked.

I have been doing all the testing on a separate outboard tank with the oil and gas mixed at 50:1.

I will continue as I get new parts and tips from this site. Thanks guys

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 16, 2020 7:08 pm

floater wrote:My alarm is a constant beep beep beep...


I think you mean the alarm is a continual cadence of BEEP BEEP BEEP, and not a constant BEEEEEEEEEEEP.


floater wrote:....but it sounds like it is breaking up like you are getting interference in the beep sound or the speaker surface itself may be cracked.


You use the pronoun "it" twice in that sentence, but I am not sure what "it" refers to in either use.

What is the first "it"? What is the second "it"?

Are you trying to say the SOUND of the aural alert sounder seems to be intermittent in a way that suggests the sounder is really trying to produce a continual BEEEEEEEEP sound and is not modulating the sound intentionally to have a cadence of BEEP BEEP BEEP?

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Tue Jun 16, 2020 8:47 pm

The little speaker under the console is breaking up when beeping. [The little speaker under the console] is making a multiple beep beep beep sounds. There is no steady beeeeeep sound. The aural alert under the console sounds like it's broken, like old speakers used to [sound] when they dried out and the cone split.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby biggiefl » Wed Jun 17, 2020 9:24 am

Since you have thrown so many parts at it, why not try changing the speaker-alarm?
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Wed Jun 17, 2020 3:03 pm

I wasn't aware you could order just the speaker-alarm. I thought it was part of the main wiring bundle. I will look it up and see. Thanks for the tip

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Fri Jun 19, 2020 8:33 pm

I was playing with the motor again this evening. I shorted the blue-white wire from the Motion Sensor to the block, and with the key in the run position, engine off, and the alarm started beeping. I replaced the motion sensor with a new one and the alarm still goes off with the engine running. The water pressure gauge reads 10-PSI at about 1,200-RPM. All this testing is leading me to believe that the alarm module itself may be the cause of the BEEP BEEP BEEP problem.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sat Jun 20, 2020 7:54 am

floater wrote:The water pressure gauge reads 10-PSI at about 1,200-RPM.


There is not a sensor in the alarm system that monitors the cooling water pressure.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Sat Jun 20, 2020 7:56 am

floater wrote:I shorted the blue-white wire from the Motion Sensor to the block, and with the key in the run position, engine off, and the alarm started beeping.


The alarm emitting BEEP BEEP BEEP is the condition you are trying to stop. I don't see what insight was gained by this most recent test. My inference is the alarm was emitting BEEP BEEP BEEP in either case.

In a previous post I explained to you how the motion sensor circuit is most likely involved in a comparator. The input from the notion sensor is not a steady state signal. It is an alternating current signal that is proportional to the speed of rotation of the drive shaft of the oil pump, and I presume that signal is compared with another alternating current signal from the Switchbox which is proportional to the speed of rotation of the engine, for the purpose to determining if the pump input shaft is rotating in proportion to the crankshaft.

Your notion that you can simulate a normal condition by simply disconnecting or grounding one those alternating current sensor signals and cause the alarm to stop sounding seems very unlikely to be accurate to me.

The motion sensor is not likely there to just detect ANY motion. It is likely there to detect that the motion of the pump drive shaft is in proportion to the crankcase motion, or at least that is my inference.

I am a bit confused that you have the factory service manual. Surely the factory service manual must have some advice on how to diagnose an alarm. I DO NOT have the factory service manual, but I would expect the factory service manual must give some further insight into how the alarm system works or at least how to test it.

For many years outboard engine factory service manuals were written for service mechanics who were presumed to have almost no skill or familiarity with anything electrical, so those manuals usually provided detailed test procedures with instructions on how to perform a sequence of simple tests in a systematic manner to find the cause of an electrical problem.

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Sat Jun 20, 2020 11:26 am

I have the Seloc service manual for Mercury engines

By shorting the two wires running into the alarm module from the Motion Sensor I thought I could trigger an oil alarm and this appeared to happen as the alarm went off and wouldn't stop till I turned the key off.

I've replaced the Motion Sensor and the sleeve on the oil pump drive shaft and I'm still getting the continual BEEP BEEP BEEP.

The automatic oil mixing system appears to be working asthe oil level in the [remote] main tank did go down past the mark I had made on the side.

Using an infrared thermometer I found the cylinder head temperatures to be between 98 and 103-degrees-F after idling for 20 minutes and a little motion around 200- RPM.

A new problem has occurred now. The engine will not accelerate to more than 2000 RPM, and the engine is stumbling and hesitating.

I've read that [the cause] could be a faulty Switch Box assembly. Everything electrical seems to pass through these double stacked assemblies. There is a testing method for the Switch Box assembly. I will read up on that and see what else I can find.

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Mon Jun 22, 2020 7:13 pm

I did more testing today to find out why the 1991 Mercury 200-HP engine is signalling an alarm with a BEEP BEEP BEEP:

  • I ran a pressure test on all six cylinders; they are all showing 110-PSI. I believe this rules out any internal damage caused by overheat.
  • I tested the resistance on all three wire sets coming out of the [stator coil assembly]; they are all within specification.
  • I tested the output voltage from the [stator] and it varies between 29 to 42 Volts AC depending on engine speed.
  • I tested the output of the rectifier and it is putting out 13.0 to 14.6 Volts DC.
  • I tested for spark at the plugs with a spark [gap] tester. I found that the Starboard cylinder bank was showing good spark. However the Port cylinder bank was showing weak to no spark.

I looked at a wiring diagram and zeroed-in on the two Switch Box modules. My Seloc Manual said to test for bias [differnce] between these two top and bottom Switch Box modules. The Switch Box modules [in some sort of resistance test] showed 14.1-Ohms and 14.4-Ohms, both in specification. I swapped the modules and found that the Starboard bank was now being affected and had a weak to no spark condition.

Since the engine automatic oil mixing system appears to be working as it should, and since the water pump impeller was good impeller, and since there was a good stream output at the tell tale, and since the cooling water pressure was 10-PSI on a gauge, I'm starting to think [the actual cause of the BEEP BEEP BEEP alarm] may not have been due to an oil mixing problem and or an engine overheat problem.

On the upper Switch Box module, the one that appears to be bad, there is a green wire going to the Alarm Module. This green wire connects and shares a post at the Switch Box that has a Green-white wire that feeds Coil Number 4 on the Port Bank. I now believe ( and hope) that the failing Switch Box module triggered the Alarm Module.

I have two new Sierra Switch Box modules part number 18-5775 on the way. I hope this will fix the hesitation, stumbling, and inability for the engine to accelerate beyond 2000 RPM. As well, I hope the Alarm Module is still in good shape after all this [testing]. Thanks for all the tips and ideas. I will post back after I install the new Switch Box modules.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Tue Jun 23, 2020 10:46 am

Thanks for the continued flow of test results.

As I mentioned earlier in the discussion, the detection of a problem with the oil pump shaft rotation depends on comparing two signals: a signal from the motion sensor on the pump input drive shaft; and a signal from the ignition system (from a Switch Box module). The basis of detecting an alarm condition is when the frequency of either of these two alternating current signals is no longer proportional to engine crankcase speed.

The intention of the alarm is that the signal from a Switch Box module will alway be available and will always be proportional to engine crankcase speed, and that the signal from the oil pump drive shaft motion detector would be likely to become abnormal due to a gear drive failure and be detected by this comparison. However, perhaps unwittingly, the alarm system responds in the same manner if the signal from the Switch Box module becomes out of proportion to engine crankcase speed; in that situation the alarm is not detecting what is was designed to find, an oil system problem, but instead the alarm system detects a spark ignition problem. It also detects a failure of the alarm system itself.

This appears to be what is occurring with your 1991 Mercury 200-HP engine: there probably is no fault in the oil pump drive shaft speed; the fault is the Switch Box module that was supposed to send a reference signal has failed. This also contributed to the poor engine response and inability to accelerate under load: half the cylinders were not getting spark.

As a general design of an alarm system for oil supply, I have not been impressed with this Mercury alarm system. There is no sensor that actually detects the flow of oil from the pump to the gasoline mixing common-connection. And, as we see here, the alarm system is quite easily fooled into an alarm if a Switch Box module fails.

In another earlier reply I also mentioned that a failed Switch Box module could create an alarm. Based on your on-going narrative of testing, I think this will be the case.

ASIDE: failure of the spark ignition primary current generating and spark timing device, or what Mercury calls a Switch Box module, is a well-known source of problems with Mercury engines that use these modules. The original Mercury parts were probably made in Mexico. Check that Switch Box module for an indicator of where it was made.

The aftermarket engine electrical part manufacturer CDI makes replacement electrical parts for many Mercury engines. These parts are made in the USA and have been designed for improved performance and reliability. The CDI ignition parts are sold with a two-warranty, which is more or less unheard of for electrical parts. I don't know anything about Sierra-brand replacement parts. I would have suggested CDI as a recommended source.

Replacing both Switch Box modules at the same time is probably a very good plan. Apparently if one fails the general recommendation is to replace both with new modules.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby biggiefl » Tue Jun 23, 2020 12:21 pm

I'm starting to think [the actual cause of the BEEP BEEP BEEP alarm] may not have been due to an oil mixing problem and or an engine overheat problem.


I told you that on June 16th.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Tue Jun 23, 2020 4:15 pm

Sierra-brand Switch Box modules are made by Mallory. Mallory has been making engine electronics for decades and is a leader in the automotive industry.

Yes biggiefi you did mention that in a previous post.

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Re: Mallory, Sierra, CDI

Postby jimh » Wed Jun 24, 2020 9:33 am

floater wrote:Sierra-brand Switch Box modules are made by Mallory. Mallory has been making engine electronics for decades and is a leader in the automotive industry.


There is a long and detailed history of the Mallory company at

https://www.holley.com/brands/mallory/

In the earliest days Mallory was located in Detroit, and not too far from where I grew up on the city's west side.

I know Mallory ignition products were very highly regarded at one time in automobile engines, particularly for racing and competition, and that their marine products were mostly for inboard engines, usually automotive engines adapted for marine use. I am not familiar with Mallory being associated with two-stroke-power-cycle outboard engine ignition systems, or that they are the OEM for replacement Mercury Switch Box modules sold under the Sierra brand. I can't find much on-line information about Sierra-brand replacement switch boxes from the SEASTARSOLUTIONS.COM website.

Sierra is a division of SeaStar Solutions, which was formerly Teleflex. There has been much consolidation of marine electrical and electronic manufacturers in the past ten years. You seem confident in choosing the Sierra brand replacement part.

There is also some very strange outfit making replacement Switch Box modules--I am not going to even mention their name because I don't want to lead anyone to them. I tried to visit their website, but it was a complete disaster. Their website was filled with garbage and attempts to get visitors to download applications. Based on the interaction with the website I would never consider their product.

For products that I am not personally familiar with and do not have any history of use and no first-hand experience, I tend to assess the product based on how it is presented on the manufacturer's website. On that basis, I would never consider that strange and unmentioned brand.

I found the Sierra website completely lacking in information about the product.

I found the CDI website to be excellent, filled with information, details, advice, troubleshooting procedures, and generally very supportive of their product. So CDI came out on top in website information presentation.

I think Sierra products are very widely available due to many dealers using Sierra's vast line of marine products which are often warehoused from local distribution centers and available in one-day.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Wed Jun 24, 2020 5:08 pm

I saw a few posts on a Mercury owners website that talked about Sierra being a seller of Mallory switch boxes.

I installed the two new switch boxes today and my 1991 Frankenstein Mercury 200-HP fired right up!

The alarm is no longer sounding and I was able to rev the motor beyond 2000-RPM for the briefest of moments.

I installed a temperature gauge in the console in place of the battery voltage gauge as well. Tomorrow will be the big test on the water.

Thanks to all for their help and especially you jimh for the great feedback.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Wed Jun 24, 2020 5:55 pm

This sounds like a good outcome. As the kids say: WINNER WINNER CHICKEN DINNER. (Also a lot of hockey players in Canada say that, too.)

floater
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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby floater » Thu Jun 25, 2020 4:15 pm

I took out the boat (a 1988 Revenge 20 WT) for a lake test today. The 1991 Mercury 200 ran better than it ever has.

The Mercury 200-HP engine fired-up immediately. Previously engine start usual took a few cranks to get her going. Now it fires right up on the first crank.

Acceleration from a standing start onto plane felt a little stronger.

This Switch Box must have slowly been failing over years.

Now that I've changed out the three-year-old impeller the water pressure gauge shows 13 to 15-PSI where before it shown 8 to 10-PSI.

My new temperature gauge showed a maximum temp of about 125-degrees-F. To have an actually operating temperature gauge now is nice.

The engine consumed 60 litres of pre-mixed oil and gasoline. I also caught two nice salmon. A good day to be back on the water. Thanks again to all for the info and tips.

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Re: 1991 Mercury 200 HP BEEP BEEP BEEP

Postby jimh » Fri Jun 26, 2020 9:36 am

Thanks for the report on the improved performance of the 1991 Mercury 200-HP engine after replacement of both Switch Box modules, which also provided a remedy to the BEEP BEEP BEEP alarm signal sounding continually.

Your persistence in investigating the cause of the BEEP BEEP BEEP alarm has resulted in a good solution. The difficulty in determining the actual cause of the alarm is seen in your narrative. Your engine was sounding an alarm that was intended to notify the operator of a problem in the automatic oil mixing system, but the actual cause of the alarm was not related to the oil mixing system in any way.

The actual cause of the alarm was a failure of the spark ignition control modules called Switch Box modules by Mercury. Your method of testing for spark by using an in-line spark gap test accessory was the most direct indicator of a problem in the spark ignition system. The inability of the engine to run above 2,000-RPM was also a symptom that could be inferred to mean a spark ignition problem, but testing with an in-line spark gap test accessory was the most positive indicator.

ASIDE: When a multi-cylinder engine, particularly a V6, is missing spark on one cylinder, this loss may go undetected for a long time.

Some years ago I had an 1992 Evinrude V6 engine. I found that it would intermittently operate on only five cylinders. Using an in-line spark gap test accessory, I found the cylinder that was not getting spark. Diagnosis of the problem was difficult because it was so intermittent. As it happened, the detection of the missing cylinder was possible because I had an instantaneous fuel economy indicator gauge. The onset of the spark failure on one cylinder was indicated by a slight decrease in fuel economy, as the fuel for that cylinder was not being ignited and contributed to no power output from the engine. Without that gauge, I would probably not have been able to reliably determine when the spark was missing. The problem was eventually resolved by replacement of the Power Pack, a spark ignition control module that is somewhat similar to a Mercury Switch Box.

A corollary story involves my wife's c.1991 Buick V6 3800 engine. We got this car used, and I seldom ever drove it; it was her car. When another problem occurred, I looked into fixing that problem. In the process I discovered that one cylinder was not getting spark, and apparently had not been getting any for a long time. Once I repaired that problem, the engine had much better fuel economy, idled more smoothly, and had better acceleration.

These anecdotes are indicative that in a multi-cylinder engine you can be missing a cylinder or two and hardly notice it. They also show that c.1990 spark control electronic module are now 30-years-old and can be in a failed or partially failed state.