I have a 1999 Mercury EFI, 175 on a 187 Champion that dies while running down the lake (just like you turn the key off). After the engine dies (and water rushes over the back) it will start right up and run good the rest of the day. I've replaced the fuel filter, fuel pump bulb, plugs, and water pump. Has anyone out there had a similar problem???????

Maybe bad wireing.....?

May be an early sign of the electric fuel pump trying to quit or could be a simple connection problem at the main harness pin connection or it could be the ECU or could be the kill switch acting up. Going to be hard to find under these symptoms.

Gary's right. It's almost impossible to find the problem when everythings working. You almost need to be armed with diagoniscs equiptment on the water so when it dumps, you can find it. You can jiggle and wiggle a few wires around, check all the plug-ins, but other than that, If It Aint Broken, Don't Know How To Fix It. Or if your pockets are lined with $$$$ Just throw parts at it until it goes away...........NOT!

You confirm what I was thinking. The pockets are definitely not lined w/$, I'm retired so I have plenty of time to look. The thing that gets me is I don't have to wiggle wires or anything, it just starts up after you get stopped. It bothers me because its embarassing, water comes over the back and dangerous because if anyone were following close, you could load them up. Thanks to everyone. Unless I can find a wire shorted out, I'll probably replace the ingnition and/or kill switch first......Looking forward to Fork again this spring....

okiebasser, i have the same problem with my 1997 150 merc efi. you will be going lets say 45 mph and all of sudden its dead and while the boat stops everything flies including you foreward. the weird thing it starts right up and maybe it does it again that day or it might not. i have changed all those things you have too, i was told once that it was water in your fuel. i don't if is true but their is alot of guys on this forum that will know. let me know or i will let you know if the problem gets solved. hey, welcome to the forum.

Well then, I would be checking the black/yellow stripe wire. That wire is the "kill" wire, it robs the ignition boxes of power and puts it to ground. Without power, no spark. I can't believe that it could be the stator, because it is a split system and only cause the engine to drop rpm. Nor could it be the trigger, as it has 3 pickups which fires 2 cylinders at the same time, so most likely it would also just drop rpm. Since you have two boxes, the blk/yel wire "y's" together from each box and runs to the key switch via emergency switch. There has to be a nick in the wiring harness under the cowling or someplace that this wire can go to ground, even in the control box,(if that is where the key switch is---some are mounted on the console) I have experienced the same situation years ago and found the blk/yel wire would touch itself to the block, kill the engine, and as soon as the engine dies, it would release itself. The motor would then start and run without any problems. It was so fast the if you got the timing right, you could restart the engine before the boat settled down in the water,slam it in gear and take off again. So in short, clip the wire ties at the ignitions boxes and follow the blk/yel wire both visually and by running your fingers over it. It takes the size of a pin hole in that wire to kill the engine....Oh yea! don't do this while the engine is running, you could get the shock of your like.

There are two things that can cause this problem is the fuel pump driver in the ECM or the charging system is putting out more than 15.5 volts there is a circuit in ECM that will shut the ECM off if the charging system is overcharging to protect the ECM. Also check main engine harness connection or the ECM connector....OPTI

ditto on the ecu/ecm connector
I fought the same problem ..0n my 96 efi ..
I disconnected the ecu connector .and then very carefully spread the "male pins" with a razor blade ..
only cut myself three times , however ,it been running great for two years now ..at zero cost
hope this helps

thanks for yalls input!!! it sounds like this a common problem

I've seen this exact problem caused by a loose battery connection.

The 3rd time it happened in a 5 minute period, I jerked it into neutral, restarted and never came off of plane. I did that several times that morning, until I went in for lunch and found the battery cable loose. I tightened it up with pliers, and that took care of it.

That makes sence because the ECM has to have 12volts to work.