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NEED HELP! 1995 Mercury 225 EFI

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SkeeterBoB

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I have a 1995 Skeeter 300ZX with a 1995 Mercury 225 EFI. Serial number OG257701
The problem I am fighting is when I get up on plane and running across the lake all of a sudden the motor shuts off. It feels like the kill switch is being pulled. After shut off (and the wave splashes the boat) I put it back into neutral, go to start it and it fires right back up! I have replaced all six coils, plugs, did manual fuel pump, new fuel line and check ball, had alternator tested. I am leaning towards the ignition ECU but would hate to spend the money and still have the problem. Is there a way to bench test the ECU? Anyone ever run into this kind of problem or is my Mercury possessed? Any help is appreciated. Thank you. :)
 
CDI electronics will have troubleshooting procedures, In the meantime check your main wiring harness inside connections 'the pins"male & female for proper contact. Check all grounds on coils, All wiring harnesses for damaged insulation entering engine and anywhere cowl might contact wires, batteries for clean and tight connections
 
I`d see about checking the ecu pulsar as it could well be failing when heating up breaking it`s internal connection causing an open circuit so not sending the firing pulse to the ecu. When the internal coil cools enough then the circuit will be made again and it`ll come back to life as though nothing is wrong and will pass electrical tests. It`s something very hard to fault find as it`s an intermittent fault and will only show when in use.

I`ve seen this several times when I ran my motorbike workshop plus had it happen to me while overtaking a long line of cars which was a bit scary to say the least!

Cheers, Matt
 
SkeeterBoB said:
I have a 1995 Skeeter 300ZX with a 1995 Mercury 225 EFI. Serial number OG257701
The problem I am fighting is when I get up on plane and running across the lake all of a sudden the motor shuts off. It feels like the kill switch is being pulled. After shut off (and the wave splashes the boat) I put it back into neutral, go to start it and it fires right back up! I have replaced all six coils, plugs, did manual fuel pump, new fuel line and check ball, had alternator tested. I am leaning towards the ignition ECU but would hate to spend the money and still have the problem. Is there a way to bench test the ECU? Anyone ever run into this kind of problem or is my Mercury possessed? Any help is appreciated. Thank you. :)
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The test for your ECU is to replace it with a known good one. Chances are you have a failing diode in the wiring harness. Problem is the only way to check it is to replace the harness.

In the past when these 3ltr engines had issues that were hard to find and all the components checked out good, changing the engine harness was the only thing that corrected it. I am sure can find a good used harness somewhere for a good price.
 
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