[sledstew]

I have a 1987 90 HP evinrude that is giving me problems ,here is the diagnosis. The motor is freshly rebuilt and compression is top notch , the motor starts fine but after about 30-45 seconds of running it will cough and sometimes its enough to kill the motor.It seems to me like some sort of ignition problem, here is what Ive done to troubleshoot the issue,

1) put new carb kits in it and tested VRO pump with new one = all is ok
2) tested and replaced timer base and flywheel= OK
3) tested and replaced stator=ok
4) The only thing I havent replaced is the powerpacks???
5) tested voltage regulator/rectifier= all is ok
6) checked all coil wires and coils= ok
7) All 4 cylinders have spark but it seems intermittent on both sides, a bit weaker on the starboard side
8) unhooked black yellow wire for kill switch =tested ok


Is it possible the guy who owned this before me burnt both powerpacks? It looks like he replaced the starboard pack .How do you test the packs with inexpensive tools, I have the DVA meter and a good multimeter.
Any help is greatly appreciated.

[Joe Reeves]

That cough is usually due to a slightly lean running carburetor.

Remove the carburetor face plate. With the engine running and with that coughing condition existing, stick two fingers into the carburetor throats, one carburetor throat at a time. You will be acting as a manual choke of sorts.

When (if) you find an offending carburetor, the rpms should increase slightly and the cough should cease to be. This would reveal an idle air bleed jet that has a slightly too large inside diameter.

Should the engine have a tendency to flood out with the fingers inserted, back the fingers out somewhat. Let us know what you find.

[HighTrim]

By all means follow Joes advice, but for your own knowledge for the future when checking the DVA output the orange wires from the power pack while connected to the ignition coils you should have a reading of at least 150V or more. If the reading is low on one cylinder, disconnect the orange wire from the ignition coil for that cylinder and reconnect it to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad power pack.

The following link is a DVA (Peak Voltage) and Resistance Chart for all your testing purposes.

http://cdielectronics.com/LinkClick....language=en-US

[sledstew]

I tried what Joe suggested and it didnt seem to help at all and it didnt seem to have hardly any affect on how it runs.Any other suggestions Joe???

[ezeke]

Check that the orange and blue wires from your powerpacks are running to the coils for cylinders 1 and 2.

[Faztbullet]

Since the engine is fresh built, I myself would looking for a transfer port gasket, intake gasket, improperly sealed crankcase half or damaged lower crank seal. Any leak in these areas will cause a lean spit. Also check to see if flywheel keyway is sheared. (Install a stop or indicator in #1,bring to TDC and check pointer)