CONTINUOUSWAVE

I have a 2006 Montauk 150, powered by Mercury 60-HP Bigfoot, serial 1B004506. I had some electrical problems that were caused by the engine charging system. I had to replace the regulator, stator and the starter solenoid, and the intake manifold air temp sensor.

Engine runs fine on muffs or in neutral in the water. The following behavior only happens under way after I get up on plane:

After I had all of this done the engine started working better than it ever did, in terms of coming up on plane and running between 3000 to 4000-RPM, between 18 and 21-MPH. Any time the engine speed exceeds about 3900-RPM, the engine has an intermittent behavior where the engine cuts out for a second, a single BEEP Iis heard, and then the engine comes right back. It is almost like the key was turned to OFF and then back to ON.

On the engine tachometer gauge and on the VESSELVIEW display, after the engine cuts out, the engine speed drops to 0-RPM, then goes immediately back up [to a reading of normal RPM such as 4,000-RPM]. This seems entirely unlikely, since there is no way the actual engine rotation speed goes from 4000-RPM to 0-RPM and back [to 4,000-RPM] that quickly.

If I keep it around 3900 or 4000, it will cut out and beep randomly and then come back, and maybe run normally for another ten minutes before it will do it again, randomly.

If I go over 4000, to say 4300, the engine will start [cutting out] more frequently, and if I go WOT, it will do it repeatedly every three seconds. The engine display then indicates code 341-6, throttle position sensor error code.

I have already replaced the throttle position sensor (TPS), and that did not change the behavior at all.

The only other change I have made, since it was running fine before electrical problems occurred, was I added a trolling plate that also has stabilizer fins.

See https://a.co/d/fQbfWUx.

I had wondered if the trolling was causing problems with water uptake, but that isn’t the errors I am getting and I have.


Give me suggestions [for how to remedy the problem of the engining intermittently utting out.

Note that providing gasoline from a new tank and fuel line didn’t seem to change behavior.

I am kind of at a loss..

I have replaced the TPS, the intake air temp sensor, the manifold air pressure sensor.

I have purchased a used ECM to see if it could be that—it’s in the mail—but seems unlikely.

If I am ok going 18-MPH boat speed and no more than about 3800-RPM engine speed, this 21-year-old 2006 Mercury 60-HP BIGFOOT engine works great—but I’d really like to sort this out.

Note, be methodical. Start at the beginning and work forward. Throwing parts at the symptom is expensive and not always faster.

I would "google" the cr@p out of it on all the forums before buying another part.

The symptoms read as electrical but could be fuel related.

I would investigate the ignition circuit including the key switch and the kill switch.

Thanks, that's definitely true. The stator, regulator, solenoid were all validated with readings, etc. The other three parts I changed cause I was right there when changing the TPS. I didn't test it, I did just replace based on the code, you're right.

I have been testing, including the ignition circuit for about a year now and can't find anything odd. The oddest thing is just that it only does once you're up on plane, under load. Should mention I cleaned the vapor separotor. I haven't rebuilt it (didn't replace the pump, just the filter in the foot and the one in the top of the VST) and replaced all of the fuel filters as part of regular maintenance. Did not see much crap in the filters, there was some black flecks/build up in the VST. But same behavior after, and running on small tank with new fuel line.

I just went through something similar, though I haven't taken the time to write up a report here yet. My 2003 Mercury 115 4-stroke would occasionally "stumble" briefly at cruise; as you said it was like turning the key off and then right back on very quickly. This progressed to where it wouldn't run above idle, and then finally to where it would only idle for 10-20 seconds. I spent the entire fall trouble-shooting this, including replacing the TPS sensor and the MAP sensor as well as the voltage regulator.

The problem turned out to be a slightly (and pretty much invisibly) corroded ground connector for the voltage regulator. This allowed the voltage to increase higher than normal once the engine was running, and when it reached approximately 15 volts the ECM would shut down (presumably due to over-voltage protection). Five minutes with a piece of 300-grit sandpaper fixed the whole thing.

This whole experience was like that old joke where a guy takes his car to the mechanic, the mechanic taps something with a hammer, then charges the guy $500. "$500 to hit it with a hammer? That's ridiculous!" "Nah, hitting it with the hammer was only $1. Knowing where to hit it was $499."

-Bob

Bob, thanks, [your account of finding a corroded ground connection at the voltage regulator was the cause of voltage fluxtuations] is helpful. Guess I will try that next.

Q1: How did you determine this?

Q2: did you monitor with a voltmeter while running and watch the voltage hit 15-Volts?

Q3: did you have the TPS error or other errors?

Q4: were any beeps heard when the engine cut out?

It's a long story that I'll tell in detail in another post. But what finally got me on the right track was when I got the diagnostic connector and software, and saw that the ECM was shutting down, and then immediately boot up again. This might be what your beep is telling you. A few fortuitous tests, like disconnecting the voltage regulator (and then the engine ran fine!) led me to monitor the voltage more closely. Since both the old and new voltage regulator behaved the same, and the tests on the stator coils met spec, I double-checked the ground... and voila!

Interesting, super helpful. I think might try the same thing there. Looking forward to your novella!

Based on your narrative describing the problem, my inference is the cause of this odd engine cutting out behavior is electrical in nature. Generally if an engine that is running normally instantaneously stops running--loses combustion--then immediately cures itself and resumes normal operation, the cause of the problem is likely to be electrical in nature. An immediate loss of spark in all cylinders is the only method that all cylinders in an engine stop firing immediately. A fuel restriction problem would be likely to begin to affect only one cylinder, then gradually affect other cylinders, resulting in a gradual decrease in power output by the engine, not an immediate and sharply defined cut off.

Electric circuits are often affected by temperature, and as the temperature increases, a problem can occur. However, the problem will not tend to disappear instantaneously shortly after onset, as there is unlikely to be any change in temperature--a cooling down of the electrical components--that can occur in a very short period of time.

Also, the apparently continued operation of electrical gauges showing engine speed while the engine has cut out tend to indicate that the electrical problem is confined to the engine's electrical circuitry.

All of these assessments tend to point to a mechanical problem being the cause of the electrical discontinuity in the engine circuits. The correlation with engine rotation speed is also significant, as generally higher engine speeds may result in increased vibration of the engine or at least a change in the frequency of vibration.

For those reasons I suspect there is a loose connection somewhere in the engine wiring. The suggestion that the loose connection could be in the negative or ground circuit is also good advice.

For ideas for remedies to this problem, I suggest you read my article about possible faults in the electrical circuits related to engine starting and running as described in detail in my article in REFERENCE at

Engine Starting Circuits
https://continuouswave.com/whaler/refer ... Start.html

Follow all the circuit paths mentioned in the low-current circuit. Any interruption in the ignition key switch circuit would have the same effect as turning the switch to OFF from RUN.

You have not given any information about the engine other than its brand and horsepower. There are two basic types of outboard engines: four-stroke-power-cycle and two-stroke-power cycle.

If the engine is a four-stroke-power-cycle engine the generation of spark ignition pulses is typically controlled by a crankshaft position sensor (CPS). Any loss of signal from the CPS will suppress generation. An intermittent CPS could be causing this problem.

If the engine is a two-stroke-power-cycle engine the generation of spark ignition pulses is typically controlled by a dedicate coil assembly in the engine alternator stator windings. The signal from the dedicated coil winding is applied to additional electrical circuitry, which I believe in the Mercury realm is called a switch box. A fault in the switch box could cause interruption of spark generation.

Also, typically an outboard engine will have a engine-shut-off safety switch. These switches tend to rely on a mechanical method of retaining a lanyard in the RUN position. Check carefully that the engine shut-off safety switch lanyard is properly and completely seated in position.

ASIDE: my wife's car had what turned out to be an intermittent CPS. But its failure was heat related. The car would be driven on several short errands, then left to heat soak for a while. Then it would not restart. I would get a call, and come to the car to diagnose the problem. By then the engine had cooled down, and the car would start and run normally. This went on until my wife insisted we switch cars. The problem finally occurred while I was using the car. After some rudimentary checks--including discovery that the V6 engine was running on only five cylinders due to a bad connection at a spark coil--I could not find the cause of the problem. I then speculated the cause might be the crankshaft position sensor. Getting to the CPS was a bit of a chore, so I asked my local garage to please just replace the CPS, do not do any diagnostic time. For a rather modest labor and parts charge, they replaced the original CPS. The engine ran perfectly after that repair for many years, until we finally sold it. I mention this because loss of the CPS signal immediately stopped that engine from having any spark generation.

Also, when chasing the cause of problem and not having a certainty of which part is causing the failure, my general rule is to replace parts in reverse order of their cost, that is, replace the cheapest part first, the next cheapest is that does not work, and proceed in that order until you conclude with the most expensive part. As parts go, a CPS is not going to be very expensive.

Thanks jimh, that article is helpful, will use in my investigation.

This is a 60hp EFI 4-stroke. I have not changed the crankshaft position sensor (CPS) yet, will add to my list to test. I had similar experience with a Hyundai V6 where a failing catalytic converter, which results in higher heat in the cat which sits right over the CPS on that engine, cooked the CPS. Cats were more expensive than the car, so I moved on.

I did check the safety lanyard switch: it seemed mechanically sound (not saying it couldn't be a connection). I also tried flipping it on and off real fast, and wasn't quite the same behavior (no beep). The behavior really feels like the the key gets turned on and off real fast. So this ground connection is starting to make me think it is a possibility. Going through grounds is pretty straightforward, looks like I might be in for some work if I need to go through every other connection.

Thanks.

Here is the final resolution to the problem of the Mercury 60-HP BIGFOOT engine tended to cut out about 3,900-RPM

I kept fighting this problem. I replaced the manifold absolute pressure (MAP) sensor and the throttle position (TPS) sensor again with no improvement.

I also replaced the engine control module (ECM). Nothing.

I did some testing on the harness. Nothing.

I checked and did work on all the ground. Nope.

I finally gave in. As a mechanic's son I don't love taking something to the shop, but I was beat and there is a local shop with a good reputation (and a long wait list and commensurate shop rate).

I was gratified that the cause of the engine cutting out above 3,900-RPM stumped them as well. They did the same things as me. Used a spare harness, completely disconnected the motor from the boat. did work on all the grounds. They couldn't find anything.

They also came to the same conclusion as me: tThe motor was simply shutting off. Like resetting. The error codes were red herrings. After some scratching of heads and staring at the wiring diagram, the tech noticed the ECM and fuel pump all are in line with the same relay. He replaced it, put it back on the dyno and it ran fine. So I picked it up and water tested (to save costs).

Pretty much same behavior, only less predictable. So I took it back. They played with it so more (didn't charge me for the shop time on this part) and noticed that it did really seem, like other GoldenDaze here mentioned, the voltage draw would suddenly increase and then motor would turn off. As the tech studied the wiring diagram some more he determined that the [ignition spark] coils were also along the same path/relay. So he started replacing the [ignition spark] coils with a spare one he had (used on an Optimax engine).

He replaced #1, no change. He eplaced #2, seemed to perform perfectly on the dyno. So he called me and said he'd like me to take and test it and see if it is better and then let him know. He said he couldn't be sure it was fixed, but if it was better he suggested I change all the coils.

I took it out and it was much better. No beeping and shutting down until 5,000-RPM, and then very sporadically.

Based on that, I ordered four new coils (replacing both the used Optimax one and the new CDI one I had replaced earlier). I [enthusiastically installed all four new coils]; I took the boat for a test run; I was able to run the Mercury 60-HP BIGFOOT engine up to full throttle and hit 32 to 34-MPH boat speed with no [erratic engine cutting out]. She's back!

Now, thinking back through succession of events:

• engine stopped charging and the fuse coming off of the regulator was melted.
• the Stator and Regulator both tested like they were bad, replaced both with CDI products.
• the steering pivot froze up and I had to replace that, involving splitting the powerhead-- probably no relation;
• the starter solenoid seemed to go bad and sometimes would engage like a phantom, and I replced it;
• the engine started missing; I replaced spark plugs and spark wires with no change. I also replaced #3 spark coil with a CDI coil; the cutting out stopped.
• the engine started the crazy single beep and momentary dying, but that was irregular and not predictable.
• the cutting out seemed to happen once warmed up so wondered if it was air temperate sensor; I replaced the air temperature sensor; no luck.
• finally got a throttle position sensor (TPS) error when I pushed the engine to repeatedly beep; I replaced the TPS, but nothing changed.
• I got a manifold absolute pressure (MAP) error in addition to the TPS error; I replaced the MAP sensor; no change.
• I checked the wiring harness, but did not find any defect or problem; no change.
• I bought a used engine control module ($400) and installed that; no change.
• Took the engine to the shop; got the outcome described above in my narrative.

The total cost of the parts I have thrown at fixing this cutting-out at high engine speed problem, including the coils that actually worked, is about $1,300.

Maybe I should have bought the 2014 60-HP Command Thrust engine for $5,000. But I am happy to have my boat back and working.

I hope this account of solving the cutting out problem might help someone else with a similar problem.

Because all of these components were powered by the same power distribution circuit. [the cause of the problem] was definitely hard to diagnose.

The key to [solving this problem] was the sudden loss of power and sudden return of power, like on-off behavior. It seems regulator, stator, and [spark] coils are key things to check here.

I'm glad that you got the problem resolved! It does seem like a very strange solution. But as Sherlock Holmes said, "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." Let's hope so, anyway!

To get the update and know the remedy that cured the problem is always the best outcome--for you and for this long thread. Thanks for the follow-up post.

In the case of the 60-HP engine, it seems a bit unusual that all FOUR spark coils needed replacement. Perhaps the four OEM coils were all part of a bad batch of coils. Or perhaps the spark generation circuit was providing unusually high voltage. Generally the spark ignition coil primary is powered by a separate winding on the stator assembly, and the voltage output from that coil may not be regulated by the voltage regulator. The voltage provided by the spark ignition winding would tend to increase with engine speed, and that would produce higher spark voltage in the coil secondary winding. That explanation correlates exactly with the onset of the problem.

Q5: By any chance are these spark ignition coils the "pencil shape" coils used by Mercury in some other engines? Those pencil coils have a reputation for rather short service lives.

POST SUCCESS CHECK

If you still have the original spark coils, you should give them a close visual inspection, looking for any sign that there was arching in the coils. I mention this based my account below.

As it happens, a few years ago I had a somewhat similar problem with my E-TEC V6 225-HP engine. After running essentially perfectly for over ten years, one day I noticed that the engine actually missed a couple of times. This was quite a surprise, as the engine had NEVER missed a beat ever. The path to the remedy of the problem was much faster for me, because the engine management module (EMM) service code log had recorded a few instances of a specific ignition spark coil appearing to have a short to ground. Visual examination of that spark coil reveal evidence that there had been an arc from the internal coil, through the coil base, and to engine chassis ground. I described this in more detail in an article at

E-TEC Engine: Maintenance History After Ten Seasons
https://continuouswave.com/forum/viewto ... 530#p46530

If you give the four coils that were removed a very close visual inspection, you might find some residue from an arc to ground.