2003 mercury outboard cuts out at wot

Started by lewis_is_bassin, April 03, 2017, 09:47:23 AM

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lewis_is_bassin

Hello everyone, I am having a little bit of trouble with my outboard and hoping someone can give me some advice. Recently my 2003 mercury 4 stroke efi outboard starting cutting out at wide open throttle (and it only cuts out then). When starting up, it idles perfect and runs at low RPM's.  Naturally I figured it was something to do with the fuel,  so I replaced the fuel lines, checked for air leaks (none that i could see or hear), replaced the fuel pump, changed the spark plugs, checked the air vent, drained the old gas and added new fuel, changed the fuel filter along with the fuel/water separating filter, and lastly put a primer bulb (ball).. When i took it out, it ran great for about 10 minutes  and then it starting cutting out once again. I am a little lost for what it could be, any ideas before i take it to the mechanic??

Lee Smith

It could easily be a thermostat problem.
Builder of Custom Personal Bassin' Rods

Oldfart9999

Could also be an electrical problem that shows up as the motor warms up.
Rodney
Old Fishermen never die, their rods just go limp.

Princeton_Man

Don't know much about Mercs. Hooking it up to a computer may save time and money depending on who's computer it is. Sounds like it's pretty surely rpm/ignition related.
Stratos 285 XL Pro 150 Evinrude ETEC

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Mike Cork

Fuel was a great place to start but it looks like you've eliminated that.

I've seen coils foul as the motor temps up. To replace them all is pricy. Buy one and replace one. Run it. If it still does it swap with the next in line.

Thermostats are pretty easy too.

Fishing is more than just a hobby

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lewis_is_bassin

Thanks, I didn't even think of the thermostat. I'll look into it and hope is as simple as that. I will keep you updated.

lewis_is_bassin

Update: installed a new thermostat and it ran a little further but cut out once again, also put an external fuel tank to rule out any fuel issues, again cut out. I bought 2 new coils so will try those.
If anyone else has any idea's of what may be causing this issue i would greatly appreciate it any advice.

Deadeye

Unfortunately this is when "nickle and dime" repairs can end up costing you more than taking it to a Mercury Tech to have it on the Computer and get it fixed right away.

However, I will add this: Check your Spark Plug Wires.

I have a 2004 Opti and it went from running great to running like crap from one trip to the next. I started it at home on water ears and with the Cowl Off I could hear a snap-snap-snap. Checked where it was coming from and one of the wires had cracked through where it laid against the head. Ordered new wires off ebay and replaced them and she ran like new.

Thornback

Another way to check for bad spark plug wires is to run the motor at night while watching for the wires to be leaking. It takes a few minutes for your eyes to adjust and there will be no sparking sound but suddenly as your eyes adjust you will see what looks like a lightening storm. It will be very faint and dancing while the motor idles just fine.

FD

How old is your battery?  I had the same problem with a 2007 250 optimax that was completely fixed with a new, high end, cranking battery. It seems mercs high performance injectors use more juice at wot than the motor produces.


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lewis_is_bassin

#10
Update: after a bit of testing I found a bad coil. Replaced that. Have been out 3 times and no more issues.
Should anyone ever have the same issue, a simple spark plug tester revealed the bad coil.

Oldfart9999

Thanks for sharing the cure, might come in handy for someone else!
Rodney
Old Fishermen never die, their rods just go limp.