Stumped on ignition problem

[Kinnamon30]

Hello all. Having a problem with spark on my 25 hp outboard. It is a 1990 evinrude E25TELESB. It has been a project motor that i picked up a couple months ago. Did the typical carb cleaning and rebuild new water pump and a couple other odds and ends i didnt care for. Fired it up for the first time and idled great. Put it on the lake and again idled great. Ran it at half throttle for about 100 yds or so and she started missing like crazy. Brought it home and started doing some testing the past week. Have good strong spark at idle and higher rpms but then like you threw a switch starts missing spark at higher rpms. Take her back to idle and the normal spark returns. It never kills the motor but seems to miss every other spark cycle. At idle spark will skip a 7/16 gap and a little more. Ohms tested both coils which both tested 252 ohms when cold (maybe should test once warm and missing?). Compression is about 112 in both cylinders cold and slightly a tad lower once hot. About 105 to 110. Cleaned all matting surfaces for ground wires ect. No wires are damaged or corroded. Thinking either power pack or coils are getting hot and failing but was looking for other thoughts or reassurance. Also forgot to mention plugs and wires are all new. Champion plugs set to .30.

Thank you for any input!

 

[Kinnamon30]

Also wondering if anyone has ever seen a faulty kill switch that test ok. Wondering if under vibtation loose internals can ground out the switch and cause spark loss? Sounds possible in my head

 

[racerone]

Test run with timing light hooked up 1 cylinder at a time.----Observe the flashing light when motor acts up.----Overheating ?

 

[Kinnamon30]

I dont suspect a overheating problem unless temp sensor is bad. With missing spark what will the timing light tell me that a spark tester wont? There is no spark to trigger the timing light.

 

[oldboat1]

My guess is the under-the-flywheel power pack. Go to the marine engine site for some instructive details (find you engine, and click on ignition).

 

[racerone]

???----You would use the timing light as a " poor man's scope "----So if the light flashes steady at idle and does not flash steady as you speed , up it is telling you there is a spark issue.----May help you determine which cylinder is the issue !!

 

[Kinnamon30]

My guess is the under-the-flywheel power pack. Go to the marine engine site for some instructive details (find you engine, and click

My guess is the under-the-flywheel power pack. Go to the marine engine site for some instructive details (find you engine, and click on ignition).

I

My guess is the under-the-flywheel power pack. Go to the marine engine site for some instructive details (find you engine, and click on ignition).

Thank you