Evinrude 4 stroke 70 problem
 

I sure hope someone has solved this problem I have had since the outboard
was 1 1/2 years old. The first 1 1/2 years it was perfect, but then OMC
died. It's a late 1999 model. Engine starts instantly, accelerates on plane
super quick, after 30 seconds loses power in a cylinder every 5 seconds for
about 3 miles. After that runs perfectly all day. It doesn't matter if I let
it run for 15 minutes before I take off or right after starting the motor.
It has been to two certified Evinrude mechanics almost all summer for the
past three years. The computer shows no codes, only that it has 100 or so
hours on it. The fuel is clean and fresh, lines are good, new plugs & wires,
one dealer installed a new temp sensor, the battery amperage is correct, and
it won't act up in a tank at all. One mechanic changed out the switch and
speedometer unit, actually ran it on the water 3 times and experienced the
same problem. He concluded it was the battery not being big enough and
replaced the battery and said it was fixed. The very next time out it did
the same thing. Recently I have noticed a slight stumble at idle (we troll
with it) very occasionally, maybe every 10 minutes or so. It doesn't die, it
has not left me stranded. Both mechanics claim to have called Evinrude about
it. One mechanic said it didn't appear to be the same cylinder dropping each
time. He actually took his laptop hooked up to it on the water test.

I realize this is hard to explain unless you have experienced it. Thanks for
any suggestions.