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2010 Mercury EFI 30 Weird Stalling Issue

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BigOtuna

Member
2010 Mercury EFI 30 – Won’t Idle or Hot Start Without Throttle (Video + Full Diagnostic Info)
Motor Info:
  • Model: 1A30413FK
  • Serial: OR354314
  • Hours: ~60
  • Year: 2010 Mercury 30HP EFI 4-stroke
Primary Issue:
  • Starts and idles perfectly when cold. 100% of the time
  • After getting the motor HOT won’t restart or idle. 100% of time
  • Will crank but not fire unless you give it ~¾ throttle in neutral
  • Even then, dies when dropping back to idle
  • Bypassing the IAC (manually introducing air) = instant start. Plug in IAC it dies
  • Runs great on plane, but docking and trailering are a mess at the end of the day
Voltage Concerns (Possible Cause):
  • New voltage regulator was previously outputting 14V at RPM, 12V at idle
  • Now only puts out ~12V max — drops into 9V range at idle when hot
  • EFI computer shows battery voltage dipping to 9V at idle (see video)
  • Fuel pressure remains solid at 40–42 PSI when symptoms happen
  • Stator tests normal hot and cold with DVA meter
  • Could low voltage at idle be keeping the IAC or ECU from operating correctly?
  • Is something possibly frying the voltage regulator?
📹 VIDEO – Live EFI Data on the Lake:
(Shows battery voltage dropping when motor is hot and idling)
What I've Replaced/Tested:
Fuel System (Fully Redone Due to Old Fuel when purchased):
  • New fuel tank
  • New primer bulb (no anti-siphon valve)
  • New low-pressure fuel filter
  • New high-pressure fuel filter
  • New low-pressure fuel pump
  • New high-pressure fuel pump (OEM)
  • Injectors sent off to be cleaned with screens (Sent VST to be cleaned too)
Cooling:
  • New impeller, wear plate, housing
  • New thermostat
  • Temp sensor tested — resistance tracks properly with temp in software and with voltmeter
  • Poppet Valve working like it should (Pee's stronger under higher rpm)
Electrical/Sensors:
  • New used IAC valve
  • New used TPS sensor
  • New used voltage regulator
  • Stator tests OK (hot & cold voltage are same on all coils) Tested with DVA meter
  • Coils not tested yet, CPS sensors not tested yet
Fuel Types Tried: (Acts like vapor lock so I was convinced it was fuel for a while...)
  • 87 octane, 91
  • Ethanol-free
Other Engine Stuff
  • Compression Good (Cylinder 1 slightly lower like normal)
  • New OEM Spark Plugs Gapped Correctly
  • 100 Hour Service done this spring

Looking for Advice:
  • Why is my ECU voltage so low?
  • Is there a recall on this machine or known issues like this?
  • Could low voltage kill the IAC/injectors/ECU idle circuit?
  • Is there a known Mercury EFI voltage cutoff threshold?
  • Could a poor ground or corroded connection be causing voltage loss under heat?
  • No Codes through Diacom
Any help or ideas are welcome — trying to fix this the right way and want to stop throwing parts at it, and also avoid the dealers...
 
Last edited:
I found this old service bulletin that might effect these motors. I will add jumper and report back, maybe ecu is not getting a proper ground? This might be some of my weird data in Diacom. Stay Tuned!
 

Attachments

  • EN_27 (1).pdf
    191.3 KB · Views: 130
Serial number does not come up 1A30413FK
Serial numbers should be a number, a letter, and 6 numbers. Deleting the FK and replacing with 1 thru 0 comes up with 4.3 Mercruiser

Voltage is to low.

Looking at a EFI 30hp manual list it having a 15amp Alternator

Are you hearing the single beep on start up?

What type and size Bat is installed?
 
Hi there! Thanks for chiming in!

No beeps on startup, red light visible for 2 seconds then disappears. Attached serial and model number and manual for motor i am working with :)

https://www.manualslib.com/manual/2126168/Mercury-25-Efi.html

Battery is new as of last year, interstate marine battery. (Cranking not deep cycle). Tests great with internal r around 2.1. Cold Cranking i think its over 500.

The manual states outboard has a stator alternator and has high rpm and low rpm coils! I thought the low was going but test great with dva meter.

Headed to lake tonight to check that ground cable to see it that solves my voltage issues.
 
BigOtuna said:
I'm not getting any codes through my Rinda Diacom. Would their be any other reason there is not a beep? I don't think it ever has beeped since I owned it. Any ignition issues at the console of the boat?
Click to expand...
Sorry to many forums
Could be beeper was not installed/connected

The manual does not list AGM so you should be ok with Interstate

The voltages are still low and until that is brought up to where it should be there can be many issues
 
AllDodge said:
Sorry to many forums
Could be beeper was not installed/connected

The manual does not list AGM so you should be ok with Interstate

The voltages are still low and until that is brought up to where it should be there can be many issues
Click to expand...
Ok it does beep under console of boat. We're getting 12.5 volts at idle and 14 WOT. At the lake now I'm gonna get her hot and see what happens
 
Ok. So in this video I added the ground as per the service manual i mentioned in my 2nd post. I got up to temp and motor started dying like normal. I hooked up with computer and here are the results. Much Better voltage and no stalling.


So here is where it get confusing. Motor is up to temp, hot, has not stalled once with diagnostic cable hooked up, I disconnect the power off my diacom cable94039a, and the motor dies instantly. I touch the positive clamp to the terminal, you can hear High Pressure fuel pump running for a few seconds then turn off. Motor fires right up and wont die as long as diacom cable is plugged in.

That video is uploading right now... So odd. So its electrical messing with the fuel injection. I need to do this again and bring my fuel pressure gauge and noid kit..
 
AllDodge said:
Have never disconnected or connected Rinda stuff when motor was running, it is always done with motor off.
Click to expand...
Yea I don't think you're supposed to says it in my manual. My motor has to be running to log, but it would never stall on diacom. Tonight I forgot to shutdown before removing clips and it died. Not intentional or planning on doing it again, but maybe I stumbled upon something.
 
In talking with Rinda and looking at Page 2A-5 in service manual:

"The diagnostic cable connection supplies power to the ECM. Disconnecting sensors and actuators while the ECM is powered
up in the special service mode, will cause faults to be displayed in the faults status screen. These faults will not be recorded in
the memory fault hours. The CDS will not clear (erase) faults hours at the time of this service manual printing."

When ECU is being powered by diagnostic cable, it will not die when hot. It runs completely fine. When diagnostic cable is disconnected, ecu voltage drops and engine dies. So this means when motor is hot, (over 160), ecu voltage is dropping low enough until motor dies. I am having trouble deciphering where the 12v comes into the ECU, or does it receive AC current from alternator stator, rectify it it within the ECU itself then send it to the regulator?

This also explains why I can pull start this motor and it will fire on the 2nd pull. The first pull "primes the ecu with voltage", the 2nd starts motor. Where as just cranking I'm not getting the voltage to the ecu it needs to fire.
 
From the manual. "This electronic control module (ECM) is an alternator driven component. It does not require a 12 volt battery source to function. As the flywheel is rotated by the recoil rope or with the electric starter, the ignition stator generates voltage to energize the ECM, ignition coils, and the high pressure fuel pump."

So it looks like I need to test the alternator stator again with the DVA meter again... hmmm
 
My buddy had a motor same as your (Merc 30hp) but was electric start. I bought the rinda connector 94039 which has a Pos and Neg alligator clips which are connected to boat Bat and powers up my Techmate Pro. I connected, he started motor, read codes, he shut down the motor and I removed clips


Look at page 47 and 48
https://www.rinda.com/acro/outboard_supplement_v6.pdf

Your motor has an alternator stator but also converts the AC voltage to DC volts, in short it does similar as a self contained Alt but components are spread out. The ECM does not use AC volts, only DC, same as Rinda scanner
 
AllDodge said:
My buddy had a motor same as your (Merc 30hp) but was electric start. I bought the rinda connector 94039 which has a Pos and Neg alligator clips which are connected to boat Bat and powers up my Techmate Pro. I connected, he started motor, read codes, he shut down the motor and I removed clips


Look at page 47 and 48
https://www.rinda.com/acro/outboard_supplement_v6.pdf

Your motor has an alternator stator but also converts the AC voltage to DC volts, in short it does similar as a self contained Alt but components are spread out. The ECM does not use AC volts, only DC, same as Rinda scanner
Click to expand...
Yea this is the same setup as mine with the alligator clips. I'm electric start too. I love Diacom its a great system.

I haven't had time to tinker with the boat again, but since I have no issues when Diacom cable is on powering ecu, its leads to think:

Ecu is not getting correct voltage from alternator stator when hot OR Ecm is bad.

I need to test Volts with engine running as I think that will tell me the real issue. (Both hot and cold) I have not found an easy way to do that, I might be able to pin behind the connector with my needle pin kit where the wire come into the connector. (as the boat will NOT run with this connection unplugged.)

If DVA readings while running hot are significantly lower than cold, that would indicate a problem with my stator powering ECM if I am correct. If this voltage stays consistent, I am thinking my ECM is shot. Attached are my current readings without running volts.
 

Attachments

  • SKM_C45825072910420.pdf
    144.6 KB · Views: 39
More DATA for you data nerds! Here is the full stator test and my conclusions. Stator alternator is not performing at hot temps supplying ecu with proper voltage to operate. When ECU is on diagnostic cable, it is powered by direct 12 volts from battery and does not die at idle. My diagnosis based on this data, stator is not operating to specifications while hot, thus needing replacement.

Enjoy!

Mercury EFI 30 – Combined Stator DVA Readings (Cold vs Hot)

| Test Context | Test Leads | Coil Function | Factory Spec | Cold Reading | Hot Reading |
|-----------------|------------|--------------------------------------|-------------------------|---------------|--------------|
| Engine Running | a → f | ECM Charge Coil | 16V | 12.5V | 10.7V |
| Engine Running | e → f | Ignition Coil (mid/low) | 16V | 12.3V | 10.1V |
| Engine Running | b → c | Ignition Coil (mid/low) | 13V | 12.7V | 12.5V |
| Engine Running | c → f | Ignition Coil (mid/low) | 13V | 13.6V | 12.5V |
| Engine Running | d → c | Ignition Coil (high speed) | 218V | 212V | 191V |
| Pull Start | a → f | ECM Charge Coil | 24V | 22V | 23V |
| Pull Start | e → f | Ignition Coil (mid/low) | 24V | 24V | 23V |
| Pull Start | b → c | Ignition Coil (mid/low) | 38V | 36V | 37V |
| Pull Start | d → c | Ignition Coil (high speed) | 46V | 44V | 44V |
| Electric Start | a → f | ECM Charge Coil | 20V | 19V | 20V |
| Electric Start | e → f | Ignition Coil (mid/low) | 20V | 20V | 19V |
| Electric Start | b → c | Ignition Coil (mid/low) | 36V | 30V | 31V |
| Electric Start | d → c | Ignition Coil (high speed) | 36V | 32V | 32V |
 
Last edited:
Here is a more acceptable display for data. Going to trace some wires and see where they all go to double check function.
Mercury_EFI_30_DVA_Combined_ForumStyle_FINAL.png
 
AllDodge said:
Never worked on one of these so I'm not much help
Does show all voltages are lower than spec cold and hot
Click to expand...
I love the theory of operation. Motor will run on its own without a battery connected. But when the ecu is not being charged correctly, problems!

Ordering a new stator alternator here soon, in the meantime, I have ecm powered by a separate 12 volts from a battery and it runs fine. 6 hours on lake and no issues 2 days ago in 90 degree heat and legit 84 degree water temps.

Oem stator is 600 bucks, I don't own a flywheel puller or holder so I might get it quoted out at the dealership. Pretty easy job if you have the tools. Found puller and holder for about 125 on Amazon. We shall see!
 
New stator is on! The flywheel did have an abundance of "rubber grime" on inside of it. Just a thin coating im assuming from the timing belt. I cleaned it, and installed new stator, torqued everything down and will lake test tonight! Stay tuned.

Hindsight.... I should have just cleaned flywheel, then retested old stator to see if that grime effected the readings. For science of course!
 
Ok fellow nerds, here are the results! No stalling on lake, ran the whole time without dying.

stator_voltage_table.png



stator_voltage_comparison.png


  • Biggest improvement hot:
    • ECM charge coil (a→f) + mid/low coil (e→f) while running → no longer sagging into the 10–10.7 V range, now holding 13.6 V.
    • Electric start b→c hot jumped from 30 V → 36.4 V.
  • Overall stability: New stator holds values much closer to cold readings when hot — the voltage drop-off problem is gone.
  • High-speed coil stayed healthy in all tests.
  • Strange some readings were better hot than cold....


Problem solved for now!
 
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