1987 Evinrude 70hp Spark ?

[MTX]

Motor starts and idles fine. Carbs link'd and sync'd. No power at WOT. 8mph on 16ft ranger. With engine running pulled off lower plug wire, engine sputtered but runs reinstalled wire, engine back to normal. Pulled middle plug wire engine died. Reinstalled wire, started motor. Pulled upper plug wire, nothing, engine continues to run with no noticeable change. With upper wire pulled can hear noticeable sparking sound. I swapped plugs and wires to different cylinders the problem does not follow wires or plugs. I suspect a ignition problem. Any help troubleshooting would be much appreciated.

 

[emdsapmgr]

Check to see if any spark from the plugwires is shorting to ground. Run the engine in the back yard at night. With the cowl off, look for spark flashes. If you pull a plug off while running and it makes no difference, then the plug has no spark, and that cyl is not contributing to helping run the engine. Weak ignition systems may spark a plug when it's pulled out of the powerhead and touches the block. But it may not fire when the engine is running under compression. Takes a lot more voltage to fire a plug under compression. You may want to do some ignition troubleshooting first. Check out the ignition troubleshooting guide for your exact engine
at this website: cdielectronics.com. Check out the cranking voltages requirements on the stator and timer base. The check to see if you have any voltage on the coil output pins.

 

[MTX]

Thank you, the website is very helpful. I'll do some troubleshooting.

 

[jakedaawg]

Why not start with an open air gap spark test on the engine. Set tester to 7/16". If it jumps that then revisit your top carb.

 

[joetheis]

If you swapped @ wires and plugs, I thinking, coil.
try swapping @ coils?
Joe
Take any advice I give with a can of beer er 2!

 

[MTX]

Swapped coils, problem did not follow. Looking more like fuel issue. Any suggestions ?

 

[jakedaawg]

Did you do the open air gap spark check. It is a necessity.

 

[flyingscott]

What is your compression and are all your carbs closed at an idle

 

[MTX]

Sorry for ignorance, can you describe an open air gap spark check. I'll recheck compression. Checked a couple months ago but don't remember # but all cylinders were even.

 

[jakedaawg]

It's a tool that you hook a plug wire to aND then hook tool to ground. Turn key and observe spark. Set it to 7/16" I think you can rent one at many tool stores or buy one if your gonna work on your own stuff. It's just the single most used tool for an outboard guy. That and a compression gauge. Every motor gets checked every time there is a problem.

 

[MTX]

Compression all within few lbs. of 120.

Will find spark tester and let you know results.

Thanks

 

[David Young]

I bought this one from my local auto parts store, less than $10

 

[MTX]

Got spark tester and set to 7/16", had spark on all coils. I'm thinking it's time to pull carbs and overhaul all three. Any other suggestions before I do that ?

 

[jakedaawg]

Nope. Sounds like a plan