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Anyone have 25 or 30 HP staring issues? ECU? erratic Tach?

B

boardhauler

Contributing Member
Has anyone had an issue with a 25 or 30 HP 4 stroke that would not start?

I have a Mercury 30 HP EFI ELPT 2007. It is the same engine as the Tohatsu and Nissans.

I got it used. It ran OK for 2 times out on the water. The second trip it shut down and would not start.

I get no pop when trying to start it (electric start). The tach jumps up to 500-1000 rpms and drops quick to zero.

I checked spark and see it spark 2-3 cylinders then nothing.

I have been through everything that I can think of. Checking with factory manual (Mercury) which seems to list the incorrect Ohm values for almost everything.

Coils
entire fuel system (incl. repairing regulator that was stuck open, new filters, checked injectors and screens, HP pump, float and seat, etc.)
Fuel rail pressure is 40+ psi, solid.
IAC, IAtemp sensor
oil pressure switch
temperature sensor
fuse
wiring
plugs (new), old ones looked fine.
charge regulator
remote controls (they are new) & wiring
kill switch & entire circuit
battery (full charged)
I can see the number one cylinder exhaust port open and close when I rotate the engine by hand.
idle exhaust port (was plugged with mud dobber nest)
compression (reading 110 psi)

I replaced the pulser sensors and stator for fun, and after I tapped the ECU and it popped 2 times, then nothing, can not get it to repeat.

I think it is the ECU. I have been looking for a used one, and everyone says they are getting tons of calls for them.
 
Failed ECUs are rare, but go ahead and run the tests on it to confirm. Also verify all grounds -- often overlooked.
 
pvanv said:
Failed ECUs are rare, but go ahead and run the tests on it to confirm. Also verify all grounds -- often overlooked.
Click to expand...

Thanks Paul,

What test are you referring to? I called a few shops and they said the Mercury factory ECU reader is of little help.

I checked all the grounds that I could find. I even added a jumper ground between the starter and block per a service bulletin that I found.

Todd
 
Chris,

I have the Mercury service manual 90-899182R01, but I do not see any chapters with a similar title.

I have been through the maintenance chapter, fuel and elec system and test specs as well as all the others. I did not see any references to checks for the ECU.

pvanv said:
I was referring to the chapter in the MFS25/30B Factory service manual.
Click to expand...
 
Did you do the ohm meter tests of the coils? Did you check exciter coil resistance? Did you check ecu charge coil resistance? It has an alternator -- not a stator. Is there voltage going to the ignition coils? Tohatsu has a special connector and software to query the ECU. Have you checked that?
 
I checked the ignition coils. None of the Ohm readings matched the Mercury service manual listed numbers. But they all appeared consistent.

With my spark board, it looks weak. It only fires 2-3 times (cylinders) then nothing (when I hold the key), it stops sparking all together until I stop and crank again.

Same deal with the Alternator readings. I picked up a second alternator and checked them both off the motor. Same readings on both.

Then I put the second alternator on, no change.
I did rap on the ECU after the alternator swap and got it to pop 2 times, but it would only repeat it once when I rapped on it again. Never again after that.

I did the same with each pulser pickup.

I do not have access to the software and connector to check the ECU. The local shop did not have the correct connector either.

pvanv said:
Did you do the ohm meter tests of the coils? Did you check exciter coil resistance? Did you check ecu charge coil resistance? It has an alternator -- not a stator. Is there voltage going to the ignition coils? Tohatsu has a special connector and software to query the ECU. Have you checked that?
Click to expand...
 
Here is the MSRP on a new ECU:
3AC064014MECU, F30B$1266.67

Most dealers will discount to around $1K.
 
Paul,

Have you used a TechMate Pro on this ECU? I have one and it says it needs to be running to test it??? If I tell it, it is running, It shows the ECU number and 0.0 running hours. Any idea if this is an indication of ECU health? I can see throttle position, engine temp, and ambient temps displayed.

pvanv said:
Go for it. That is well below dealer cost on the actual Tohatsu part.
Click to expand...
 
Paul,

I think I found some more interesting information out while testing.

Below is a picture of my service manual and, in pencil, the ohm measurements I was getting.


Today, I found some instruction on a simpler way to test a 3 phase rectifier/regulator. Using my multimeter Diode test setting and checking flow from..........

positive lead (on positive rectifer/reg red wire) to each of the 3 yellow AC leads (from alternator to rectifier/reg)
negative lead (on positive rectifer/reg red wire) to each of the 3 yellow AC leads (from alternator to rectifier/reg)
&
positive lead (on negative rectifer/reg black wire) to each of the 3 yellow AC leads (from alternator to rectifier/reg)
negative lead (on negative rectifer/reg black wire) to each of the 3 yellow AC leads (from alternator to rectifier/reg)

I show voltage/flow BOTH directions between the negative rectifier/regulator lead and all 3 AC yellow leads.

Also.......I removed the ECU and looked at the back. I can see the tops of 5 capacitors. 4 of them look bulged up, which is consistent with a failed cap from my experience. However, it is hard to tell is they are popped/bulged or maybe the potting compound was thicker on these 5.

Is it possible that the engine would not run because the regulator/rectifier is blown? That the tach and voltage gauge drop off when cranking because power is not being supplied from the regulator/rectifier?

Is it possible that the blown regulator/rectifier killed the ECU?

pvanv said:
Go for it. That is well below dealer cost on the actual Tohatsu part.
Click to expand...
 
Paul,

Do you have the Tohatsu service manual? Would you give me the specs it lists for the rectifier/regulator and ignition coils? I'd like to compare them to the Mercury manual to see if they are correct.



pvanv said:
You would have to call the manufacturer of TechMate. I use OEM stuff...
Click to expand...
 
I have the Tohatsu manual for the MFS 30B.
If the rectifier/regulator were shorted, it would blow the fuse. The ignition does not get its power from the regulator; the battery charges from it.
Coils should read almost infinite ohms from HT lead to ground, but just a few ohms to ground from the low volt side.
What kind of meter are you using?
You do realize that the rectifier is a bridge diode arrangement, so that if one diode is bad, it would still limp, right? Just not charge well.
 
Paul,

Yes, I understand that the Ignition and ECU have separate coils on the alternator/stator. And that the seperate charging coils power the rectifier/reg which sends power directly to the main POS battery/starting lead.

I'm using a Extech 430.

Yes, I understand the general rectifier bridge diode schematic, but not this one specifically.

I was concerned that since, I am getting .65 volts (in diode test mode) from the Yellow HT AC lead (red meter lead) to ground (black meter lead), the regulator/rectifier may have blown the ECU. I don't want it to blow a new one.

I am also getting an open OHM reading between the rectifier/reg positive feed/12 v charging lead and each yellow HT AC lead & between the 12v charging lead and ground. The manual lists that these readings should be 5k and 6k ohms respectively.

Todd



pvanv said:
I have the Tohatsu manual for the MFS 30B.
If the rectifier/regulator were shorted, it would blow the fuse. The ignition does not get its power from the regulator; the battery charges from it.
Coils should read almost infinite ohms from HT lead to ground, but just a few ohms to ground from the low volt side.
What kind of meter are you using?
You do realize that the rectifier is a bridge diode arrangement, so that if one diode is bad, it would still limp, right? Just not charge well.
Click to expand...
 
Not sure about your testing of the rectifier. Never did it that way. As for your readings on the rectifier, a lot depends on the meter you are using.
 
UPDATE

I figured out the problem.

The rectifier regulator went bad. The AC (supply from alternator) to the ground wire reads flow both ways with a diode checking meter. No bueno.

It blew out the ECU.

These Mercury ECUs are poorly built with very little protection. They can blow from a bad fuel pump (different side of the board) OR in my case, a bad rectifier/regulator.

I was able to find a used ECU to test. It turned out to have the fuel circuit blown. I was able to run the engine by using my ECU to charge the fuel system/pressure. Then swap ECUs and run the engine until fuel pressure dropped.
 
Figured out the issue. I hope this helps many others.

The computer/ECM is fragile, expensive and unrepairable. a huge number of otherwise serviceable engines with many years left, are sitting in parts yards due to the expense and difficulty troubleshooting this issue.

If you have a fuel delivery issue. It may be the hp fuel pump is an aftermarket model that draws slightly more amps than the factory pump spec. This is the high pressure pump. The factory replacement is extremely expensive and many knock offs exist. They can also damage the fuel
circuit in the ECM. But no worries, a relay to turn on the hp pump with the ignition switch fixed it, perfect.

Or, if the ECM is still sending 12v to actuate the Hp pump, but it is an aftermarket and draws too many amps, use the ecm circuit to actuate the relay. Which can now deliver adequate amps to the hp pump.
 
I have a 30b and yesterday it ran good after changing the high pressure pump and all the sudden it went in to safety governor mode and starting a continuous beep and died just short of the bank. I paddled it and loaded up and today I pulled the pump out( was working when hooked up to battery) put it back and doesn’t pump. Cut the wires and jumped to the battery and spits gas. Any help would be appreciated
 
jessemcgregor1985 said:
I have a 30b and yesterday it ran good after changing the high pressure pump and all the sudden it went in to safety governor mode and starting a continuous beep and died just short of the bank. I paddled it and loaded up and today I pulled the pump out( was working when hooked up to battery) put it back and doesn’t pump. Cut the wires and jumped to the battery and spits gas. Any help would be appreciated
Click to expand...

What brand pump did you put in? The aftermarket pumps are not worth risking it. If it was not an oem merc or Tohatsu pump, it may have blown the ecu circuit that drives the pump.

I would double check to see if the pump is running. If not, you may need a mew ecu. Alternatively you can direct wire the pump and see if it runs. If it does, then you can run the pump off a relay that turns it on with the ignition switch. You’ll have to be careful not to leave the switch on and run the pump when the engine is not running. If the circuit from the ecu provides enough power to run the relay, it could turn on the pump also.

the issue is that the factory ecu can not provide the amperage draw that a aftermarket pump needs. It may not even provide enough for a damaged or aged factory pump.

Also, their is a ecu, typcial failure that effects the ignition/spark circuit that is different from the fuel pump circuit failure. Their is no work around for this one that I know.
 
I have had this Tohatsu 30HP engine for two years without any major issues, then few weeks ago after a half hour it has stopped and I'm unable to fire it up.
I have checked the fuel injection system, all sensors and switches (MAT, Water temp sensor, oil pressure switch, stop switch, MAP, TPS, ISC, etc)
The only thing I can pinpoint is the FFP high pressure pump wouldn't get any voltage. Would anybody know what is needed in order to sort this?
I can only that it's not the ECU as it costs and arm and a leg to replace it. Since I'm living in Hungary it is nearly impossible to find a garage who could fix this.
Any help would be greatly appreciated.
 
jessemcgregor1985 said:
I have a 30b and yesterday it ran good after changing the high pressure pump and all the sudden it went in to safety governor mode and starting a continuous beep and died just short of the bank. I paddled it and loaded up and today I pulled the pump out( was working when hooked up to battery) put it back and doesn’t pump. Cut the wires and jumped to the battery and spits gas. Any help would be appreciated
Click to expand...

Hi Jesse, wondering if you resolved this issue as I had same problem. Mine occurred after I used an aftermarket high pressure fuel pump which seems to be a problem according to other comments on this thread. Appreciate your feedback on how you sorted it?
 
Jethronone said:
Hi Jesse, wondering if you resolved this issue as I had same problem. Mine occurred after I used an aftermarket high pressure fuel pump which seems to be a problem according to other comments on this thread. Appreciate your feedback on how you sorted it?
Click to expand...

Yes, any of the aftermarket fuel pumps will kill the ECU. They draw too many amps of current, which is supplied by tiny wires from the ECU.

if your lucky, you can wire your pump to a switch and power direct from the battery +\charging circuit. After your remove connection to the ECU.

if your unlucky, you’ll need a new ECU and New factory fuel
pump.
 
Thanks I really appreciate the feedback. I think I will invest in the genuine fuel pump and go from there. Then I need to decide if its worth mortgaging the house if the ECU is also gone!
 
boardhauler said:
Yes, any of the aftermarket fuel pumps will kill the ECU. They draw too many amps of current, which is supplied by tiny wires from the ECU.

if your lucky, you can wire your pump to a switch and power direct from the battery +\charging circuit. After your remove connection to the ECU.

if your unlucky, you’ll need a new ECU and New factory fuel
pump.
Click to expand...

Before you do that, disconnect the fuel pump from the ECU, wire the pump to 12 volts. And see if the engine starts and runs normal.

The ecu should just try to send voltage to the fuel pump as it always does. The fuel pump will build pressure with 12 bolts and a decent size wire.

The ECU switches power to everything though ground or negative. Which I believe is why it is so vulnerable. Dc current actually flows from negative to positive. I am not exactly sure of the mech engineering, but I believe that leaves the ECU carrying a higher load as it sees the voltage before running the pump. Than when a aftermarket pump demands more amps, it tries to give it and blows out the board.
 
Thanks. Should I also disconnect the ground from the ECU and earth it to the block? Unfortunately I won't be where the outboard is for a few weeks so won't be able to try until then.
 
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