Stalled while idling now it cranks but no star or sparks

[Ignatios]

Hello all,
I have twin Mercruiser 350 mag mpi 2000
I had an issue with the (charging board or switch batteries board(?)) so I switched some cables around long story short, both engines idle nice and started with less than full crank now when I moved cables around in the switch board and turned the switch to battery 2 I was running only one engine and it kind started hesitating the idle went down ran erratical and hesitant then a wining noise came out of the alternator it was as if it came under heavy load and it stalled, went back to start it I noticed that it didn’t make the 2 long beeps and the buzzing noise of the fuel pump didn’t come on, it cranked but fidn’t start I checked to see if there is a spark but it was dead no spark at all no electric coming to the fuel pump, I tried starting the other engine but the same exact thing and this second engine was not even running.
Any ideas or suggestion would be very grateful .

 

[alldodge]

Did you move cables around while the motor was running?

 

[Ignatios]

Did you move cables around while the motor was running?

No sir I did not but I switched the dial around of the switch board

 

[alldodge]

ok, if you have Bat switches that make connection before breaking connection there is no issue. If they break before Make then a ALT may have fired. If ALT spiked it could have taken out the ECM. Hope the worst might have blown a fuse

Need to find out if the cables are still connected to the motors as they should. Trace Bat power from switches to starter post. If they are good, trace power to the key switch. The check for power at the Main Power Relay MPR

 

[Ignatios]

I checked the fuses at the switch board and at the halm then at the fuse by the ecm all good both engines cranks but seems like no power at the distributor or at the fuel pump or even the buzzer when turn the ignition on.
What is the MPR and where would it usually be, my boat is Larson 330 cabrio

 

[alldodge]

The key powers up the ECM and MPR. If they don't get power, nothing works
Fuses and relays.

 

[Ignatios]

ok, if you have Bat switches that make connection before breaking connection there is no issue. If they break before Make then a ALT may have fired. If ALT spiked it could have taken out the ECM. Hope the worst might have blown a fuse

Need to find out if the cables are still connected to the motors as they should. Trace Bat power from switches to starter post. If they are good, trace power to the key switch. The check for power at the Main Power Relay MPR

…and by the way the ALT did spiked very high

 

[alldodge]

Crossing fingers
In that case you might have break before make switches, and they should never be switched when a motor is running

 

[Ignatios]

Crossing fingers
In that case you might have break before make switches, and they should never be switched when a motor is running

I searched no tipped circuit breaker did not find any fuse… power from key to the starter it cranks good and strong but no spark at the coil no fuel pump kicking no buzzer first you turn the key on the weird thing that the starboard engine was not running when this happened it was completely off and now both engines has the same symptoms

 

[alldodge]

Try to retrace your steps, maybe something was disconnected

Other wise trace 12V from the key to the coil with key on

 

[Ignatios]

Try to retrace your steps, maybe something was disconnected

Other wise trace 12V from the key to the coil with key on

At the harness on the engine there is 2 poles that they barely have power very weak

 

[Ignatios]

Just checked electricity at the coil with the key on but nothing there I also the the power to the fuel pump again nothing there.

 

[alldodge]

At the harness on the engine there is 2 poles that they barely have power very weak

2 poles, are they the ones on the back of the 50 amp breaker?
Have 12V on the main starter post?

 

[Ignatios]

What’s the worst case scenario I could have

Try to retrace your steps, maybe something was disconnected

Other wise trace 12V from the key to the coil with key on

Try to retrace your steps, maybe something was disconnected

Other wise trace 12V from the key to the coil with key on

What’s the worst case scenario I can have do you think?

2 poles, are they the ones on the back of the 50 amp breaker?
Have 12V on the main starter post?

ye sir the harness that is in the back of the engine the main harness, the 50 amp breaker is by the ecm this harness is on the other side of the distributor one of the poles ( the thicker one) has 12 volts plus almost 13, others none and 2 has very dimmed power.
But when I checked the cable at the starter has 13amp plus
So from the key to the batteries switch board to the starter no problem and it cranks strong, but the power to the main harness starting with the beeper by the key and power to the fuel pump and the coil there is nothing.
It seems like the harness Carries the power to the fuel pump the coil and the beeper all these are down. I don’t know where they start … I checked the fuses on the box at the helm all are on nothing got triggered off.

 

[alldodge]

ye sir the harness that is in the back of the engine the main harness, the 50 amp breaker is by the ecm this harness is on the other side of the distributor one of the poles ( the thicker one) has 12 volts plus almost 13, others none and 2 has very dimmed power.

Bat power on one side of the breaker and no power on the other. The breaker tripped. Have you pushed the breaker to reset it?

 

[Ignatios]

Bat power on one side of the breaker and no power on the other. The breaker tripped. Have you pushed the breaker to reset it?

Yes I have but nothing happened, I didn’t check to see if there is power at the 50 amp breaker though … these photos are of the buzzers behind the dashboard by the key not sure if they have anything to do

 

[alldodge]

Might have blown the 90 amp fuse on the starter. Looks square and there is a fuse inside it. Its mounted on the starter post, but it shouldn't crank if the fuse or the breaker blew

 

[Ignatios]

Might have blown the 90 amp fuse on the starter. Looks square and there is a fuse inside it. Its mounted on the starter post, but it shouldn't crank if the fuse or the breaker blew

View attachment 365282View attachment 365283

Yes it cranks strong but no start no buzzer sounds no fuel pump sound

 

[Ignatios]

I have an electrician saying without looking at it that it sounds like an ECM are gone could this be true since only one engine was running when the alternator spiked up and the engine sounded like under stress and it shut off, how could the ECM on the other engine get burned or ruined if it wasn’t running? Is this possible?
Thanks

 

[alldodge]

Normally it would only effect one engine, but I don't know how things are connected, or what voltages are at what locations and values. In short, not able to see what you see. Something is connected between the two otherwise it would not have changed anything on the other motor