f115 dropping 2 cylinders

[cyrillefrenchy]

hello yamaha gurus
this thread is about a 2005 mercury 115 4 strokes, which is a yamaha powerhead as you all know...could not get any help from mercury forums.
my problem is; sometimes i am "loosing" 2 cylinders , energised by the top coil when riding the boat, i discoverd this problem a few days ago, it is clear 2 cylinders are dropping, the rpm at constant throttle position goes up and down and i can feel clearly 2 cylinders not firing, the engine is shaking, when it happens, i disconnect the upper coil and the rpm does not change, it does change when i disconnect the bottom coil.i swapped the 2 coils, still the same 2 cylinders not firing, sometimes there is no " juice" to energize the coil..
my question is: how are the coils triggered? is it the cdi or the stator?
any help will be apreciated?
cyrillefrenchy

[boats.net]

Could be pulsor coil, number 3 in diagram
Yamaha Outboard Parts 2005 F115TLRD GENERATOR Diagram
If you have a peak reading voltmeter, it should have 26 volts at 1500 rpm's out of the pulsor coil leads(you will need a test harness to check voltage while running).

[cyrillefrenchy]

hello
thank's boats.net, i tried today again with the cowling off, the engine ran fine for 30 mn and lost the the power to the top coil again, for 10 - 15 seconds only, but several times. while someone was driving the boat, i was shaking - moving - bending the the electric harness, no difference, still loosing the top coil.
do you know what is the color of the wires i have to check on the pulsar coil?
thank you again for your help
frenchy

[boats.net]

Between white/red and black. Between white/black and black.

[cyrillefrenchy]

hello
thank's fro the reply, today i "opened" with a blade the little wiring harness going from the ecu to the coils, checked by pulling- bending the 4 wires, checked and cleaned lubricated the connectors to the ecu and the wires and connectors to the pulsar coil, did not found anything wrong, restarted the engine, ran for 2 hours non stop at 2000 rpms on forward tied up to the dock, took the boat for a 1 hour ride at 4500 rpms, ran fine....i guess i fixed the problem without finding anything wrong,i must me a bad connection somewhere between the ecu, coils and pulsar coils,it is the only thing i touched...
if it does again i will let you guys know...
thank you boats.net for your help
cyrillefrenchy