2002 Mercury 250 EFI 6 cyl- Wont turn over- no spark

[Omc729]

Hi, can anyone give some ideas on troubleshooting??
The boat has 2- 2002 Mercury 250 EFI motors on it. Boat has been sitting for a while. One motor cranks over but shuts off (might need fuel) the second motor cranks but wont start at all. We have swapped over the ECU, the starter and the CPS from the engine that does start and none were the issue. Checked all the fuses as well. I did notice there is no emergency kill switch (at all) I don't even see a wiring harness or anything. I don't know what else to check. There is NO SPARK on any of the 6 cylinders. What am I missing???

 

[Faztbullet]

There is a kill switch somewhere...

 

[Texasmark]

Slow cranking speeds (battery or cable connection corrosion problems) can affect spark generation on the one that doesn't fire at all, or as Fazt said. Manuals talk about 200 RPMs for certain engine tests for a suitable cranking speed number.

On the one that lights off and won't stay, agree on fuel problem, which could just be your not choking repeatedly till it gets warmed up or running long enough to get adequate fuel up to the engine established through the fuel plumbing from the tank (squeeze bulb used enough?); common when they sit for awhile, beside the fact that fuel could be contaminated.

 

[Omc729]

If there was a kill switch problem wouldn’t it cause both engines to not turn on?? I only see one opening where the kill switch should go but there is no actual switch in it and no wiring found behind it either. I followed the cables from each key switch I found the black cable with yellow tracer and I can’t seem to find it clipped anywhere or as if it was connected to the emergency kill switch. Voltage on all 3 batteries are 12 drop to 11 at cranking. I do see that the fly wheel isn’t spinning as fast as the one engine that does crank over when hitting the key to turn on but the starter is good. I just can’t thinking of what im missing here.

 

[Omc729]

Rechecked wiring out of both key switches and no cables to a kill switch

 

[Texasmark]

I have an Optimax manual for 2000 115 thru 150 hp engines. May be similarities, especially since remote controls aren't necessarily engine unique.

Pin 1 of the 8 pin connector in the engine that goes to the remote control is the Black/yellow stripe kill wire. This comes from the ignition switch and the kill switch on the throttle control, or located remotely if not on the control. The purpose of the kill switch is to shut off the engine if the lanyard is pulled, flipping the switch, just like turning the key to OFF shorts out Pin 1.

Being a dual installation, you might have a combined kill switch such that both engines would be shut off if you exited your seat......but that doesn't fit your situation....so I'd be looking at an ignition switch as the smoking gun.

I'd pull the 8 pin connector from the engine that won't start, put the ignition switch in any position except OFF and ohm out the remote cable end. at the engine connector interface to battery - (ground) and pin 1. If it shows a short or thereabouts then your engine won't start problem is on that wire.

Pull the plug on the engine that will start and check that resistance of pin 1 to ground of that one. If open, which it should be if the ignition switch for that engine isn't in the OFF position, then your smoking gun is a shorted black/yellow on the bad engine, or a short/bad switch on the control for that engine. Since you swapped ECUs you eliminated a lot of guess work there. Good thinking.

Ohm out pin 1 and come back. It's 6:20 Central Daylight now. I'll be up another 3 hrs. Get back and I will respond.

Edit: Can you swap remote control cables between engines? That would be your quickest answer as to where's the smoking gun.

 

[Omc729]

Thanks for the info... swapped the cables with the engine that works and it still wont crank over... all my wiring seems to be fine. Is there anything else on the engine that could be bad?

I have an Optimax manual for 2000 115 thru 150 hp engines. May be similarities, especially since remote controls aren't necessarily engine unique.

Pin 1 of the 8 pin connector in the engine that goes to the remote control is the Black/yellow stripe kill wire. This comes from the ignition switch and the kill switch on the throttle control, or located remotely if not on the control. The purpose of the kill switch is to shut off the engine if the lanyard is pulled, flipping the switch, just like turning the key to OFF shorts out Pin 1.

Being a dual installation, you might have a combined kill switch such that both engines would be shut off if you exited your seat......but that doesn't fit your situation....so I'd be looking at an ignition switch as the smoking gun.

I'd pull the 8 pin connector from the engine that won't start, put the ignition switch in any position except OFF and ohm out the remote cable end. at the engine connector interface to battery - (ground) and pin 1. If it shows a short or thereabouts then your engine won't start problem is on that wire.

Pull the plug on the engine that will start and check that resistance of pin 1 to ground of that one. If open, which it should be if the ignition switch for that engine isn't in the OFF position, then your smoking gun is a shorted black/yellow on the bad engine, or a short/bad switch on the control for that engine. Since you swapped ECUs you eliminated a lot of guess work there. Good thinking.

Ohm out pin 1 and come back. It's 6:20 Central Daylight now. I'll be up another 3 hrs. Get back and I will respond.

Edit: Can you swap remote control cables between engines? That would be your quickest answer as to where's the smoking gun.

 

[Omc729]

I noticed when i open the key switch for the motor that does crank that the voltage tach goes up between 11 and 12 but on the motor that doesnt crank it stays at 10. i checked with a vom and volatge seemed fine out of the batteries. we even put all battery cables to the one that wont start and it did not make a difference in starting. im running out of options here. the engine itself doesnt seem to be the actual problem.

 

[Texasmark]

If I follow you correctly you changed out everything but the engine proper. You said won't turn over in your initial post. Put your voltmeter on the power STUD (red wire attached from solenoid) and the other lead on a metal part of the starter case, not the clamp holding it to the engine block. Attempt to start. What voltage do you read?

 

[Omc729]

12 without turning the key. Drops to 6 when trying to crank.

 

[Omc729]

Anyone have more ideas??? Please lol

 

[Texasmark]

12 without turning the key. Drops to 6 when trying to crank.

Bingo! Should be at least 10v.

You are right across the starter with nothing else in the circuit. One would assume that your engine is startable, meaning it's not frozen up or requires excessive power to spin it. That leaves the starter proper is drawing excessive current due to an internal short or worn out brush not making proper contact....shorting across armature poles.

Had you not swapped out cabling, it could have been a corroded connections between the battery and the engine but you swapped all that.

Looks like it's time to take the starter to a shop and have it tested and have the brushes inspected for wear.

 

[Omc729]

In my original post I mentioned i had already swapped the starter though. We used the one from the good motor and it still wouldn’t crank.

 

[Omc729]

In my original post I mentioned i had already swapped the starter though. We used the one from the good motor and it still wouldn’t crank.

 

[Omc729]

 

[Texasmark]

OOps, sorry I missed that.

Let's back track to your comment: I noticed when i open the key switch for the motor that does crank that the voltage tach goes up between 11 and 12 but on the motor that doesnt crank it stays at 10. i checked with a vom and volatge seemed fine out of the batteries. we even put all battery cables to the one that wont start and it did not make a difference in starting. im running out of options here. the engine itself doesnt seem to be the actual problem.

What were you doing here? Were you talking about having the voltmeter leads directly across the starter and trying to start the engine. Again, you were trying to start the engine, voltmeter leads across the power stud from the solenoid and the starter case proper and got 10 volts when you tried to start?

Earlier you mentioned having 12v and it went down to 6. What were the conditions then and where were you measuring?

 

[Omc729]

******** I checked with leads on the actual batteries as well
as in the back where they connect to engine. We know the starter is good.
If I turn both keys for both engines to the on position only tachometer for the engine that turns over actually moves up showing 12v The other tachometer for the engine thAt
wont turnover Reads 10v

What were you doing here? Were you talking about having the voltmeter leads directly across the starter and trying to start the engine. Again, you were trying to start the engine, voltmeter leads across the power stud from the solenoid and the starter case proper and got 10 volts when you tried to start?

********* below we tested it at the solenoid as you suggested it reads 12 with the key put on position but drops to 6 when trying to start it. Im guessing the loss of power is why it wont turn ovee or why we have no spark

Earlier you mentioned having 12v and it went down to 6. What were the conditions then and where were you measuring?

 

[Omc729]

Bump

 

[Texasmark]

6 volts across the starter (power stud to case) when attempting to start is the problem. The question is, is the reason in the starter.....no you said you eliminated that as a possible cause, or is the wiring to the starter corroded, no you said you swapped wiring, or is it a bad battery....can't supply the 300 amperes with 11V or better terminal voltage when attempting to start.

Back to square 1. Get on the 20V scale and don't worry about what polarity shows up. Put 1 lead on the case of the starter and the other on the battery - lead stud. Attempt to crank. The voltage needs to be less than 1 volt.

Repeat the process only this time get across the battery + lead stud and the power stud on the starter and repeat the process. If the voltage is more than 1 volt in attempting to crank, start working your way back to the battery.

Somewhere along the line you will find the 10-6, 4 volts that needs to be added to the 6 across the starter for 10 to roll the starter.

Why not go over to your working engine and take voltage meaurements and come back to the non-functioning one and make comparisons.