1989 Mercury 70 Horse dies at WOT - fuel? or electrical?

First time poster here, but I've read many different posts on this topic and have run out of ideas on troubleshooting my issue. I'm hoping to get some fresh ideas.


Here goes:

I have a 1989 70 Horse Mercury outboard, which is the 3 cyl, oil injected with the WME carbs. I'm running this on a 16ft aluminum fishing boat with a built in fuel tank.

For the past year or so, my engine will sporatically die out while running ... typically at WOT. The engine doesn't stall or miss ... it just shuts down. When this does happen, its normally during a decent run... say 3/4 of a mile or more.

There is no issue with starting after it dies ... just turn the key and your off again. No need to prime the bulb.


The engine idles well and runs strong throughout the RPM range. It has died occasionally at lower RPM's, but I normally will run close to WOT... so that's where I experience this issue most often.


Here's what I've done,

Cleaned carbs -- not disassambled, rather did the seafoam 1pint to 3/4 gallon of fuel in seperate tank

all new fuel lines and checkvalve (including fuel lines under cowl)

New fuel filter (actually replaced it twice)

New fuel pump (replaced this twice as well)

new oil lines

cleaned tank breather line (it was gummed up)



I haven't pulled my sending unit from the tank yet (hard to get at) to try and look into the tank at the pickup lines to see if anything is clogging the pickup.


Here are my two remaining ideas on what may be causing this based on reading other peoples posts on this forum
1) water in fuel?
2) electrical -- maybe a bad coil?


I would appreciate any guidance you may be able to offer as I'd like to get this outboard issue resolved

Thanks,

Fetchum

Re: 1989 Mercury 70 Horse dies at WOT - fuel? or electrical?

Sometimes at high rpm operation a old fuel line that has been baked in the sun year after year will suck shut starving the engine of gas, you might try replacing the fuel line between the bulb and the motor. Sometimes its simple things and this is cheap enough to try, good luck friend!!!

Re: 1989 Mercury 70 Horse dies at WOT - fuel? or electrical?

Bassguy 64

That's exactly what I was hoping for, but I did replace all the fuel lines including the check valve and still had the same issue today when i ran it.

FWIW, It did run much smoother and longer before the issue showed its ugly head again.

Question, is the only access to my tank where I remove my sending unit? I'm curious if some junk is floating in my tank that catches on the pickup and causes this issue.


Thanks,
Fetchum

Re: 1989 Mercury 70 Horse dies at WOT - fuel? or electrical?

Any headway on this? I just bought the same merc...