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2006 25hp 3cyl efi, weird starting issue.

E

Elkins-93

New member
Update: went out about an hour ago and pulled it one time and it fire right up. I really dont understand what the probelm Is, it’s been setting idling on muffs for an hour now, shut it off going to let it set awhile and try to pull start again.

Semi Long post. 2006 25hp mercury 3cyl efi, A few have said stator a few have said ecm. After yesterday I’m leaning towards stator. (This motor is new to me)

Got it home after doing the transom and it fired up first pull. Shut it off and restarted at twice with the pull rope and twice with the starter absolutely no problems. It ran for about an hour or so before I shut it off and didn’t touch it for roughly 3 hours. This is when it started giving trouble again (as it’s done since I picked it up and with the last guy), pulled the rope and no beep, no red light same with starter no beep no red light when turning over.

This morning pulled 11-12 times before finally getting a beep and red light and it tried to start but just didn’t. Pulled again 11-12 times before it finally got a beep and red light but no start. No response at all with the electric start.

This has me leaning towards the stator being bad and not providing enough current to wake up the ecm and fuel system for the efi except for in certain instances, once it’s running it’ll run as long as it has gas with no problems.

Volt meter hooked to battery cables without battery shows a voltage of 16.0 volts dc fluctuating upto 18.5 volts dc and anywhere in between.
 
Just got the same motor, bought it with a no spark condition. Ended up being the ECU. But I did spend a fair bit of time digging into it before I got to that point. It sounds like you are on the right track to me. The lack of a beep is supposed to be a sure sign of a dead or dieing ECU or Stator. After I replaced My ECU it was the first sign I got that let me know I had replaced the right part.

The Stator has two sets of coils that go to the ECU. One has the white wires with the colored stripes, and one has just 3 white wires. All 6 go into a black 6 pin connector.
The yellow wires (gray connector) from the stator is for a 3rd set of coils that go to a rectifier if you have it (My version didn't come with the rectifier.) and charges the battery. The voltage from the rectifier is what you are seeing at the battery wires. You shouldn't need this or the battery for the motor to run. As long as the other 2 sections are good the motor should run unless the fuel circuit has been modded with a relay, and then it depends on how the mod was done.

The Service manual has the pins in the black connector laid out as follows:
b c d
a f e
The bottom row is all white wires and should measure 1.1-1.7Ω between any two.
Top row has the colored stripes. b-c should measure and c-d should measure 11-16Ω. If you measure b-d it will be the sum of b-c and c-d.
I'd be sure to check these when the engine is cold before you are able to start it, and when it is refusing to start.
I ended up ordering a stator on eBay for mine simply because I didn't trust it due to corrosion. I did swap it out and didn't fix my no spark situation. But for information purposes my first one measured 1.6Ω and 13Ω, and the second one measured 1.7Ω and 14Ω.

I bought a Service manual on eBay (Part Number: 99-899182R01). I couldn't find a PDF version that covered 2006. But not much changed. This one here served me fine until the proper one arrived in the mail.
www.manualslib.com

MERCURY 25 EFI SERVICE MANUAL Pdf Download

View and Download Mercury 25 EFI service manual online. 25 EFI outboard motor pdf manual download. Also for: 30 efi, 25 efi jet.
www.manualslib.com www.manualslib.com
But it has you check voltage coming off the stator instead of checking the resistance. Which requires a semi specialized accessory for a multimeter.
 
OdinWethers said:
Just got the same motor, bought it with a no spark condition. Ended up being the ECU. But I did spend a fair bit of time digging into it before I got to that point. It sounds like you are on the right track to me. The lack of a beep is supposed to be a sure sign of a dead or dieing ECU or Stator. After I replaced My ECU it was the first sign I got that let me know I had replaced the right part.

The Stator has two sets of coils that go to the ECU. One has the white wires with the colored stripes, and one has just 3 white wires. All 6 go into a black 6 pin connector.
The yellow wires (gray connector) from the stator is for a 3rd set of coils that go to a rectifier if you have it (My version didn't come with the rectifier.) and charges the battery. The voltage from the rectifier is what you are seeing at the battery wires. You shouldn't need this or the battery for the motor to run. As long as the other 2 sections are good the motor should run unless the fuel circuit has been modded with a relay, and then it depends on how the mod was done.

The Service manual has the pins in the black connector laid out as follows:
b c d
a f e
The bottom row is all white wires and should measure 1.1-1.7Ω between any two.
Top row has the colored stripes. b-c should measure and c-d should measure 11-16Ω. If you measure b-d it will be the sum of b-c and c-d.
I'd be sure to check these when the engine is cold before you are able to start it, and when it is refusing to start.
I ended up ordering a stator on eBay for mine simply because I didn't trust it due to corrosion. I did swap it out and didn't fix my no spark situation. But for information purposes my first one measured 1.6Ω and 13Ω, and the second one measured 1.7Ω and 14Ω.

I bought a Service manual on eBay (Part Number: 99-899182R01). I couldn't find a PDF version that covered 2006. But not much changed. This one here served me fine until the proper one arrived in the mail.
www.manualslib.com

MERCURY 25 EFI SERVICE MANUAL Pdf Download

View and Download Mercury 25 EFI service manual online. 25 EFI outboard motor pdf manual download. Also for: 30 efi, 25 efi jet.
www.manualslib.com www.manualslib.com
But it has you check voltage coming off the stator instead of checking the resistance. Which requires a semi specialized accessory for a multimeter.
Click to expand...
I’m glad someone else chimed in that’s dealing with the same thing. I’ve pretty well narrowed it down to the ecu, I do have a direct voltage adapter coming in the mail today for my multimeter so I can test the stator output at the pins with it converted over to DC like the service manual specifies but with the battery charging I don’t see the stator being an issue but I’m going to check it anyways. I’ve found new ecu’s for about $875 shipped however I’d like to find out if there’s something I can do to prevent this from happening again or if th factory ecu’s were just prone to fail eventually.
 
Definitely check every point you can before ordering an ECM. Too much money to just try one to see if it works. From what I can tell though No spark is limited to a few components anyway. The Stator, ECM, Ignition Coils, and the Pulsers along with the wiring for all of those. I don't have enough experience to say for sure but I suspect the Ignition coils and the pulsers wouldn't stop pit from beeping when you pulled the cord.
To verify the pulsers beyond just checking the resistance, I measured the voltage coming out of them as I waved a piece of steel past them with the flywheel off.
From what I've seen there's been a few superseded versions of the ECM that I found across the interwebs.
I ordered PN: 8M0165350 for $860 ($930.96 after taxes.) Which seems to be the most recent version.
Got really lucky. The box sealed from Mercury had 2 ECMs in it. So now I've got a spare to hold on to. Googled the part number and found 1 other guy that had the same thing happen.
 
OdinWethers said:
Definitely check every point you can before ordering an ECM. Too much money to just try one to see if it works. From what I can tell though No spark is limited to a few components anyway. The Stator, ECM, Ignition Coils, and the Pulsers along with the wiring for all of those. I don't have enough experience to say for sure but I suspect the Ignition coils and the pulsers wouldn't stop pit from beeping when you pulled the cord.
To verify the pulsers beyond just checking the resistance, I measured the voltage coming out of them as I waved a piece of steel past them with the flywheel off.
From what I've seen there's been a few superseded versions of the ECM that I found across the interwebs.
I ordered PN: 8M0165350 for $860 ($930.96 after taxes.) Which seems to be the most recent version.
Got really lucky. The box sealed from Mercury had 2 ECMs in it. So now I've got a spare to hold on to. Googled the part number and found 1 other guy that had the same thing happen.
Click to expand...
What’s you serial number? Below a 252xxx or above? Mines a OR170777 so I’ve only found one ecm
 
0R130557

I noticed some websites list ECM part numbers for a range of serial numbers. Some listed them as superceding each other while most almost nothing changed year to year.

If you take the first part number from defender.coms superseded list and plug it into boats.net it pulls up the ecu for the early models.

I used PN 8M0165350. I only ran it for 10 min before I had to leave it alone until later this week. But it seemed to be running fine.
I'm hoping there were some incremental improvements where Tohatsu/Mercury was trying to make the ECMs quit failing as much.
 
Last edited:
OdinWethers said:
0R130557

I noticed some websites list ECM part numbers for a range of serial numbers. Some listed them as superceding each other while most almost nothing changed year to year.

If you take the first part number from defender.coms superseded list and plug it into boats.net it pulls up the ecu for the early models.

I used PN 8M0165350. I only ran it for 10 min before I had to leave it alone until later this week. But it seemed to be running fine.
I'm hoping there were some incremental improvements where Tohatsu/Mercury was trying to make the ECMs quit failing as much.
Click to expand...
Greatly appreciate that link, the first part number on there is the one I was actually looking at on boats.net but I’m like you and hope that newer part number that supersedes it and the others has had some improvements made in the failure areas. I’m extremely mechanically inclined but these part numbers get updated so often on boat motor parts it gets confusing, boat motors don’t make any sense in general with the problems they like to have.
 
Yeah. I think sometimes they update a partnumber just so they can charge more for the same part on a newer engine.
I'm an Amazon Vine reviewer so I get stuff to review for free. I've gotten a few parts for this motor off of there (Water pump/Fuel Pump/Fuel filter/Oil filters). And im looking at an Idle air control valve on there right now. According to its part number its for a much older model 30Hp. But I can't see a difference between it and the one for ours. If I didnt have to pay taxes on it as income at the end of the year I'd just grab it and see.
 
OdinWethers said:
Yeah. I think sometimes they update a partnumber just so they can charge more for the same part on a newer engine.
I'm an Amazon Vine reviewer so I get stuff to review for free. I've gotten a few parts for this motor off of there (Water pump/Fuel Pump/Fuel filter/Oil filters). And im looking at an Idle air control valve on there right now. According to its part number its for a much older model 30Hp. But I can't see a difference between it and the one for ours. If I didnt have to pay taxes on it as income at the end of the year I'd just grab it and see.
Click to expand...
You might look into doing the fuel pump relay mod, probably what I’ll wind up doing, saves the ecu.
 
Elkins-93 said:
You might look into doing the fuel pump relay mod, probably what I’ll wind up doing, saves the ecu.
Click to expand...
Have one ready to install.
The previous owner had the fuel pump grounded to bypass the ECM. I was kind of surprised when it started running because I'd seen videos that claimed that didnt work.
 
The bypass I've seen done they already had the fuel circuit burnt out in the ECM. So they used a time delay relay run off of the blue wire.
Then ran either battery power, or the blue wire again, across the contacts of the relay to the pump and grounded the pump.

Since I know my ECM is new. I'm thinking I might just run a regular relay off of the wires that normally go to the fuel pump. And then run battery power to the fuel pump using the relay. Im trying to find replacement connectors that match the fuel pump connection so I can make it something I can remove in the event of a dead battery to get back to the boat ramp.
 
OdinWethers said:
The bypass I've seen done they already had the fuel circuit burnt out in the ECM. So they used a time delay relay run off of the blue wire.
Then ran either battery power, or the blue wire again, across the contacts of the relay to the pump and grounded the pump.

Since I know my ECM is new. I'm thinking I might just run a regular relay off of the wires that normally go to the fuel pump. And then run battery power to the fuel pump using the relay. Im trying to find replacement connectors that match the fuel pump connection so I can make it something I can remove in the event of a dead battery to get back to the boat ramp.
Click to expand...
So everything tested within spec of what you gave me and the manual I found gave me. Except the grey 3 pin connector from the voltage regulator to the stator. My book shows the 3 pin connector having 0.29-0.43 ohms at the 3 pin connector and I got 000.7 on all three pins coming from the stator.

However I’m leaning heavily towards the ecu due to the fact Im intermittently and rarely getting spark especially in cooler temps.
 
Elkins-93 said:
Update, it was a faulty pulser coil on the starboard side of the engine
Click to expand...
I have a very similar issue to you in my 2010 25 pull start. It would start fine when it was warm outside but once it got slightly cool it wouldnt start, and would beep and light up after intermittently after about 15 pulls. I sent my ECU to Simon Performance Technology in CA and they said it was DOA and they haven't been able to get it working properly yet. Do you think a faulty pulser coil might have killed my ECU and it was a cheap part all along?
 
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