Spark on only one cylinder- 1997 Evinrude 50HP BE50TLEUC

Hey, I'm in dire need of some help!
Background: My engine only revs to about 2500rpms (sometimes over, S.L.O.W is most likely not the culprit because the engine sounds very strained at full throttle, not like a digital cutoff). I have changed sparkplugs(Qtype), spark plug wires, coil, cdi and stator. I thought that the stator fixed my problem. I verified that it fired on both cylinders with a timing light but when I tried it in the water it failed to push past said RPM limit. When I remove the top spark plug lead nothing changes, ie no spark on top cylinder.

I tried to switch positions of the primary orange wires on the coil. The blue (top) did not produce a spark on the bottom cylinder. The orange green one (bottom) only produces spark on the bottom cylinder, not the top one.

Then i tried to change the output from the timer base buy siwstching the blue and green pin in the amphenol contact. This resulted in that I got spark on only the bottom cylinder again when the orange blue (top) primary cable from the cdi was connected to the primary socket on the bottom coil, not even the top one! I know that one coil on the timer base is good but it only works on the bottom cylinder, not the top one. The timer bases measures 25 and 26 ohms.

My conclusion is that I need a new timer base. But I still seem to have a weird ground problem on the top cylinder. Why and how can I fix this? All help is appreciated!

The charge coil on the timer base fires both cylinders.--And the sensor coil on the timer base fires both cylinders.

If it helps your diagnosis , I think your motor has a "waisted spark " ignition . One coil with two leads.....the coil fires twice per cylinder per Revolution , when one cylinder is at tdc the other is at bdc ,the coil fires both plugs ....the one at tdc will fire the fuel mix and make power ,the other ,at bdc will fire the plug but does nothing ....hence the "waisted spark " term . Lots of motors do it and I believe its simply to cut manufacturing costs as you only need one coil and one triggering device . Doesnt matter which plug lead goes to which cylinder .

Wrong assumption.

racerone said:

Wrong assumption.

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How does it work then .....roughly always keen to learn

Orange / blue stripe fires the top cylinder.----Orange / green stripe fires the bottom----Blue is the sky ( top ) , green is the bottom ( grass )

racerone said:

Orange / blue stripe fires the top cylinder.----Orange / green stripe fires the bottom----Blue is the sky ( top ) , green is the bottom ( grass )

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Thank you
Make sense when I think about it ....as the op says runs on one cylinder ....which is way better than none if you dont like swimming home

Points more to the power pack when this condition exist.

Mc Tool....yamaha's both fire at the same time at least the ones I've worked which isn't many.

saltchuckmatt said:

Points more to the power pack when this condition exist.

Mc Tool....yamaha's both fire at the same time at least the ones I've worked which isn't many.

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Lots of multi cyl motorbikes do to.
Gotta confess I googled the op's model number ....saw it was carbed and assumed it would be a waisted spark jobbie .

saltchuckmatt said:

Points more to the power pack when this condition exist.

Mc Tool....yamaha's both fire at the same time at least the ones I've worked which isn't many.

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Nothing changed when it switched out the power pack. I still only had spark on one cylinder. What could cause the motor only to spark on the bottom? Even if i have a good signal from the power pack it still won't spark on the top?

Part numbers of parts you replaced?----Source of these parts?

The wonderful " Magflash " ignition system came out on the 1971 model 50 HP .-----The 3 cylinders used it starting in 1972 .---The 4 cylinder in 1973.----It never used a " wasted spark " on any of them.-----Parts / pieces changed over the years , but not the theory of operation did not.

racerone said:

Part numbers of parts you replaced?----Source of these parts?

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All parts except the stator were brand new. I Verified that all part numbers were compatible

The questions were not answered.----Good luck with the motor.