Merc 250 Verado Fuel increase

[muc]

 

[alldodge]

Guessing this is LED's on the throttle handles, and if so I have not watched for them during start sequence

The isolator (might also be a combiner) and and fuse I found


Wiring diagram


So looks like it's a combiner and haven't found anything to change House yet, but may be behind the Boat switch panel

 

[muc]

The Dual‑Engine Battery Architecture Diagram I posted comes from the
VERADO V8/SEAPRO V8 INSTALLATION MANUAL p/n 90-8M0156798
This should have been in your owners packet that came with the boat.

The Start/Stop All Engines I posted comes from the
Electronic Remote Control OPERATION MANUAL GEN 2 p/n 90-8M0180922
This also should have been in your owners packet.

It's possible that you didn't get them ---- I have worked with techs that felt it would "just confuse" boat owners, so They throw them away.
If you don't have them, I'm guessing you can call Merc for a free copy. They maybe even be available online under owners resources.

 

[alldodge]

I did find the install 8M0156798, it was in another folder

I can down load the Op manual, but mine starts port first, so the boat I'm thinking was wired wrong

Edit: found paper 8M0175493 Op and Maint

 

[alldodge]

Accomplished Gen 2 Control test SB 2025-05R2 and no beeps

Verified the pic in post 62 is a combiner

ALT test SB 2021-21
Unknown if I have isolator's or not, if they are installed they must be behind the Bat switch panel. Knees were getting to me so did measurements at motor, ALT and Bats

Key OFF Eng Off
House 12.5
SB Bat 12.67
PT Bat 12.73

Key On Eng Off
House 12.49
SB Bat 12.56
PT Bat 12.59

Key On Both Eng Run
House 14.29 to 14.30
SB Bat 14.4
PT Bat 14.5
Voltages at ALT or Motor connections the same. Thinking there isn't any isolator's because voltages at ALT are same as Bat

If I turn the keys ON and press start button before VV fully wakes up, I get beeps. Last season I could do the same and no beeps, also if I wait for VV to wake up there are no beeps. Difference between last season and this is the Bats measured slightly higher voltages 12.8

At the combiner the center post measured 13.9 to 14.1, the left post measured 13.2 to 13.5, the right post measured 13.5 to 13.8

 

[alldodge]

When starting motors using start/stop the throttle handle LEDs were lit before during and after start, run and shut down

 

[muc]

When starting motors using start/stop the throttle handle LEDs were lit before during and after start, run and shut down

This isn't how the manual describes sequence of start event. If you are talking about the LEDs on the port and stbd start/stop buttons on the aft face of the control?
Are you starting these engines with shore power and batt charger still connected and on?
But I have no hands on with this ayatem.

 

[alldodge]

This isn't how the manual describes sequence of start event. If you are talking about the LEDs on the port and stbd start/stop buttons on the aft face of the control?

No, talking about the LED's on top the throttle controls

Are you starting these engines with shore power and batt charger still connected and on?

No, shore power is disconnected
I can start or stop both motors by pressing the start/stop button once keys are turned ON. When starting the port starts first than starboard. When stopping they both stop at same time.

I can start/stop either motor individually by using the keys or the buttons behind the throttle in previous pic

 

[muc]

Looking at your voltage readings.

When you started testing had you burned off the surface charge on all 3 batts? Please make sure you do this before any testing if there might be a surface charge.

The numbers at the batts look normal and tell us that the house battery is getting charged by at least one engine.

I have not seen the voltages at the engine ever being the same as at the battery, they will always be different. Tenths and hundreds of a volt matter in these measurements. If the meter/leads aren't capable of seeing these low voltages, it's time to do a voltage drop test between the stud on the battery and the stud on the engine. Both + and - cables.
Please note that if you don't follow "best practices" when doing electrical testing ---- you might not pick up on the underlying issue. On the positive side, in this case that means taking battery measurements at the battery stud, not the ring terminal. At the engine this means at the hot stud and alternator output stud doing KOEO and KOER tests. At the starter solenoid stud when testing during a cranking event. On the negative side, at all 4 of the ground studs.
Please note that the tests in 2021-21 are just for alternator testing! I'm pretty sure Merc put this bulletin out just because techs were sending alternators back for warranty when the alternator wasn't the issue. You should also do testing during cranking, voltage drop shows up best when the circuit is under full load. This means you will need a helper or a min/max setting on your DMV.

The voltages at the the combiner don't make sense to me. If it is a combiner the voltages at the right and left studs should be higher then the center due to the diodes. Maybe look behind the area covered by the wires and see what this box is?

 

[muc]

No, talking about the LED's on top the throttle controls
View attachment 415976


No, shore power is disconnected
I can start or stop both motors by pressing the start/stop button once keys are turned ON. When starting the port starts first than starboard. When stopping they both stop at same time.

I can start/stop either motor individually by using the keys or the buttons behind the throttle in previous pic

Good, never start engines with the charger in operation.

OK, those LEDs are the neutral indicators. The LEDs I was thinking about are on the port/stbd start/stop buttons. What do those LEDs do when you do the all start?

I'm guessing the double beeps you get during cranking are due to the system not being fully awake.
A double rapid horn indicates denial of the attempted action.
You will need G3 to see what exactly is getting denied. What will happen if you continue to run the engines in this state -- I have no idea. But it is probably best to wait for the system to fully wake up before cranking.
The fact that you don't see any faults on the TechMate tells me they are CCM faults. Only G3 read faults form that computer, note that on your boat the CCM is integral to the throttle control.

I don't know why the port starts first. Guessing this might be something that can be set in G3? Would be a good question for your dealer or Merc consumer tech support? 920- 929-5040