5.0 MPI - Loss of power/ground or other alarm?

[Bdaviskar]

2002 MCM 5.0L Alpha MPI 0M616xxx ECM 555

Hello Everyone. I am trying to figure out what is causing the below symptoms. It is like someone is turning on and off the key or the kill switch very quickly. However, the gauges and accessories stay on.

Cruising along between 800 and 2000 rpms

• Quick Audible alarm/beep would sound and the RPMs would drop 500- 1000 rpms.
• The motor catches back up
• It could alarm/beep 1 time an hour or 3 times in 5 secs. (alarm does not stay constant or beep 2 times a minute)
• This would happen in gear and neutral
• All gauges and accessories stay on.
• Could happen within the first 5 minutes or hours of running.

At idle in neutral or below 800 rpms in gear.

• Quick audible alarm/beep and the RPMs drop and the boat would stall
• Then I hear the fuel pump would start just like when you would turn the boat on for the first time.
• Intermittent - May not happen for hours or 5 mins of starting the boat.
• The engine will start right back up and may run for a little while before it happens again.

The majority of the time the issue appears to happen when we are slowing down and dropping below 2000 rpms or in idle as we are trying to dock the boat.

The issue will not happen over 2000 rpm. In fact, when the boat was beeping multiple times, I speed up to 2500 – 3500 rpms. Boat runs great. I did this test multiple times, As soon as I get below 2000, the issue can start again.

Oil pressure and temperature are in normal range.

History:

• Purchased the boat last year. Ran great for the one week we were able to use it.
• The issue started the first day of this season

Actions Taken:

• Local dealer scanned the ECM. No codes were found.
• Checked every connection that I could wiggle/ move to try to make it happen again. Including the ignition and kill switch.
• Took apart and cleaned and expanded the pins on the 10 pin harness. Used Dielectric grease and snugged back together, In fact, I did this twice because it seemed like the issue went away for a day. No luck the second time.
• Removed grey wire from the tach. Still happens

Questions:

Can the ignition switch be ruled out since the gauges all stay on at the time of the beeps?

The wiring diagram from the manual shows a purple wire from the ignition switch wired to the kill switch then wired to the tach. However, when I toggle the Kill switch, the motor is killed but the gauges remain on. How is the Killswitch wired? The diagram shows the kill switch wired in series to the tach.

If the main relay is intermittingly going bad and dropping out, would it cause the alarm to sound? I plan to switch the main relay with the fuel relay and see if the issue continues.

If the interrupter switch is the culprit, could the alarm sound if the switch is dropping the RPMs?

Is there anything else I can check?

Thank you for help in advance.

 

[NHGuy]

Disconnect the battery and service every connection you can get to. Wire brush, emery cloth whatever it takes. It's a pain in the behind but it very possibly could solve your issue.
Clean the battery terminals, the grounds to the engine, the hot lead, all the main plug prongs, the gauge contacts, the ignition switch and the accessory switches. I bet you come across some sketchy contacts.

 

[Bdaviskar]

Thank you for your reply. I will check and clean every connection I can.

Would you be able to help explain the kill switch circuit. If I am reading the diagram correctly, it looks like the purple wire off the key switch connects to the kill switch then connects to the tach. The tach then powers the other gauges. If this is correct and I toggle the kill switch it should turn off the power to the gauges correct? Thank you

 

[Bdaviskar]

Went to the boat today, checked and cleaned every connection I could get to as described by NHGuy. I also re-cleaned and expanded the pins on the 10 pin main harness. I was unable to take the boat out because it was getting late. I will test this weekend.

However, if the problem is still present, I have a few Ideas I would like run by everyone to make sure I won’t do any damage to the boat and if I am on the right track.

Step 1
Run a 12 volt jumper to the wake circuit (purple wire) that is in the return after the main 10 pin plug. I was thinking of back feeding it into the Can line purple wire. This would eliminate the key switch; kill switch, gauges and the 10 pin harness.

Step 2
If the problem still continued, I was thinking I could run a ground jumper to the Main Relay. This could help eliminate or point to the ECM 555 or a grounding Issue to the ECM.

Thoughts?

Would it be ok to do the above steps without damaging anything?

Thank you in advance for your time.

 

[achris]

2002 MCM 5.0L Alpha MPI 0M616xxx ECM 555

...Questions:

Can the ignition switch be ruled out since the gauges all stay on at the time of the beeps? Not necessarily. It may be happening so fast that you can't see the instruments drop.

The wiring diagram from the manual shows a purple wire from the ignition switch wired to the kill switch then wired to the tach. However, when I toggle the Kill switch, the motor is killed but the gauges remain on. How is the Killswitch wired? The diagram shows the kill switch wired in series to the tach.That's what my diagram shows too. Therefore the instruments should be OFF when the kill switch is activated. You'll need to chase the wires and see exactly how it's been wired.

If the main relay is intermittently going bad and dropping out, would it cause the alarm to sound? I plan to switch the main relay with the fuel relay and see if the issue continues. a failing main relay would cause the alarm to sound with the normal 'powering up' sounds.

If the interrupter switch is the culprit, could the alarm sound if the switch is dropping the RPMs? I wouldn't think so.

Is there anything else I can check? Not being able to see, touch and hear the engine makes it difficult in these types of faults to suggest avenues... But, first place I'd be checking is the 20A glass fuse and its holder behind the dash. Seen too many of them with a small amount of corrosion on that causes these sorts of faults. I recommend changing it out for a 20A blade fuse (same as on the engine) and water resistant holder regardless of it's condition.

Thank you for help in advance. You're welcome.


Now a question for you. Why have you, and others do the same, not included the complete engine serial number?

Cheers,

Chris..........

 

[Bdaviskar]

Hello Chris. Thanks again for your time to answer all my questions.

2002 MCM 5.0L Alpha MPI 0M616xxx ECM 555

Now a question for you. Why have you, and others do the same, not included the complete engine serial number?

At the time, I was not sure of the last 3 numbers and I wanted to hurry up and post. I really did not think the last 3 would make a difference.. My # 0m616214

I was able to figure out one mystery. The kill switch circuit was changed. Someone added an extra purple wire from the ignition switch to the Gauges. The other purple wire went to the kill switch and they spliced right into the purple wire that feeds back to the 10 pin plug. This explains why the kill switch did not turn off the gauges but killed the motor.

Thanks for the advice about the fuse, I actually have an extra blade fuse block I will install that I was going to use on my previous boat until a tree fell on it. That's another story......

I did just replace the main relay. I now plan to replace the key ignition switch. TY

For future reference - Is it OK to back feed /Jumper 12 v or a ground (depending on which is needed) to the correct circuit for use of troubleshooting? ( as mentioned in my previous post)


Thank you again
Brian

 

[achris]

...For future reference - Is it OK to back feed /Jumper 12 v or a ground (depending on which is needed) to the correct circuit for use of troubleshooting? ( as mentioned in my previous post)...

A completely acceptable and well used troubleshooting methodology. It only requires that the person doing it fully understand the circuit so as not to do more harm.

Chris..........

 

[dingbat]

Problem:
RPM related issue presented as a momentary loss of power and or under voltage condition below 2xxx rpm

What Is relative to rpm and voltage?

Hint: there is not a fuse or switch on the boat that is rpm sensitive

Charging system - rpm sensitive alternator supplies power to storage device aka battery

Measure battery voltage while problem is occurring.

What is the output of the altenator above and below your problem rpm?

When was the last time the battery was load tested?


Quite possible you have a parasitic drain dropping the voltage to the lower limited under low charge conditions. I’ve seen a bad starter (shorted winds) present in a similar fashion

 

[Bdaviskar]

Thanks Chris.

Is there a way for me to add "5.0 MPI " to the title of this thread? I should have done that in the beginning, This way when we fix it, it would be easier to find by others with the same issue.

Thank you.

Brian

 

[Bdaviskar]

Problem:
RPM related issue presented as a momentary loss of power and or under voltage condition below 2xxx rpm

What Is relative to rpm and voltage?

Hint: there is not a fuse or switch on the boat that is rpm sensitive

Charging system - rpm sensitive alternator supplies power to storage device aka battery

Measure battery voltage while problem is occurring.

What is the output of the altenator above and below your problem rpm?

When was the last time the battery was load tested?


Quite possible you have a parasitic drain dropping the voltage to the lower limited under low charge conditions. I’ve seen a bad starter (shorted winds) present in a similar fashion

Thanks DingBat

I have not checked the batteries (Just the connections) . I do have a dual battery system. I will check output on the alternator and report back. I haven't load tested the batteries yet.......

Thank you

 

[achris]

Thanks Chris.

Is there a way for me to add "5.0 MPI " to the title of this thread? I should have done that in the beginning, This way when we fix it, it would be easier to find by others with the same issue.

Thank you.

Brian

Hi Brian,

I tried to add the '5.0MPI' to the title, but it failed. In past versions of the forum software it could be done, but apparently the software writers deemed that this feature was no longer required. :facepalm:. I have requested it be put back in. We'll see how long it takes... (don't hold your breath. )

Chris..........

 

[Bdaviskar]

Hello Everyone. I figured I would update my progress and ask a few more questions

I was able to test my last steps of cleaning the main 10 pin plug again and replacing the Main Power Relay.

The boat ran great for a day and a half. As soon as I thought We fixed it.... "BEEP" (cruising around 1800 rpms after WOT)

It seemed that 2 out of the 3 times I checked the main 10 pin plug (expanded the pins) and reinstalled, the issue goes away longer than one day. This time it only beeped once while using the boat for an hour on the second day.


My Next Steps.

1. Jumper / Add a positive 12 v wire to the Wake Line - Purple wire, This way I can rule out the kill switch, Ignition Switch and/or the 10 pin harness.

2. Change inline fuse to a blade fuse.

3, Check and clean the dual Battery Switch ( I skipped over the first time)


Questions Please.

1. Where would you place the jumper? I am thinking of trying to find a plug to fit on the 4 pin diagnostic plug (purple wire) connecting it to a 20 amp fuse then to the battery. Thoughts?

2 Just to make sure I am on the right path in assuming this is a loss of power, ground or battery issue: Am I correct to say that the SINGLE beep/alarm is the key? A bad spark plug. plug wire, coil, rotor or cap would not give us a SINGLE beep/alarm? And of course, no codes when scanned at the Merc Dealer.

Thank you for updating the title of this thread.


In response to dingbat:

Since the issue only happened once, I was unable to get the reading at the batteries during the time of the Issue. However, I did take the below readings

12 .6 volts at the Batteries.
9.8 was the lowest it went on Multimeter on start.
13.8 - 14 volts in Idle and after a few minutes 2000 rpms. This was at the batteries and 4 pins diagnostic plug (purple and black wires).
14 volts in neutral at 2000 rpms. This was at the batteries and the 4 pins diagnostic plug.

Thank you for everyone's time and help!

Brian

 

[Bdaviskar]

I believe we found the issue (Knock on wood). While trying to locate and replace the 20 amp fuse (as recommended in an earlier post), the main 12v red wire was actually connected to a circuit breaker. My 2003 SD237 Hurricane SunDeck used circuit breakers instead of fuses. It was corroded and broke off in my hand while I was tracing the wire. I skipped over this step the first time as I was afraid to cut the zipped ties to the messy wire harness and went right to the ignition switch.

I installed the new blade fuse block and rewired the circuit to the ignition switch. 3 days and 4 trips with no beeps! Looks like I have a lot of rewiring to do at the gauges.

Thank you, everyone, for all your help!

 

[Bdaviskar]

I wanted to post my notes in case it could help someone else. Below was my list of items to check as mentioned above by NHGuy and achris. I also received a wiring diagram for my engine from Mercruiser customer service to help me understand my boat wiring. Basically, check everything in the circuit.

Connections and or items to check:

• Battery (Positive and Ground)
• Dual Battery switch
• 90 circuit breaker on Starter
• 50 amp circuit breaker
• Red Purple wire at 10 pin harness to the helm- clean and expand pins to ensure connection.
• Connector that connected the 10 pin harness to the front wiring harness.
• 20 amp fuse or circuit breaker– This was the connection I believed caused my Issue.
• Ignition switch
• Front Gauges
• Kill switch
• Purple wire at the 10 pin harness - clean and expand pins to ensure connection.
• ECM pin B-18 – where the purple wire connects to ECM
• ECM Ground pins B 16 and 24
• Ground Splice 104
• Engine Ground
• Battery ground

If all else failed, I was going to send out my ECM to get tested over the winter.

Just a few quick notes:

• I assumed the issue was after the ignition switch and gauges because my gauges never missed a beat while I loss power/voltage. It was so quick that the gauges did not see the loss of power / voltage. (as achris stated in an earlier post)
• I was not able to find the issue during the wiggle test. I had to trace every wire and clean connections as NHGuy stated in an earlier post.
• For the cost, I just replaced the main relay and was planning on replacing the key ignition switch.
• I also tried to run with the grey wire off the tach. I saw this in an old thread as well as a mechanic told me to do this where they scanned my ECM-555.
• This was for a quick audible alarm like when you turn the key, Not a constant or double beat alarm.
• No codes were retrieved when scanned

Hope this helps………..

 

[LimitedClear]

I'm having the exact same problem with 2007 Crownline 210 LS with 5.0 MPI. I had a corroded terminal on a 40 amp circuit breaker by the battery. I cleaned it and still have the issue. Where would the 20 amp breaker or fuse be located? I've traced the power line, the parts of it that are visible and can't find anything else. I'm thinking of just replacing the 40 amp breaker and main relay to eliminate those. I don't want to just toss parts at it and never find the issue. This thread has been very helpful so far. I at least know where to look to pinpoint the problem.

 

[Bdaviskar]

For my boat, the 20 amp circuit breaker was located on my dashboard. The 20 amp fuse could also be located behind the dash as achris stated above in post #5. You should be able to find it if you trace the main 12 volt red wire backwards from the key ignition switch to the 10 or 14 pin main harness. This was after I disconnected the battery ground and had the battery switch off.