1995, 115 horse Johnson

[nymack66]

I am not sure if this engine is equipped with the SLOW feature , if the engine is overheating it will activate and shut off firing on some cylinders..Remove the T-stats as test ..
This year also has a diode in the harness..
Test for SLOW
Engine will not rev beyond 2500 RPM:
1. Use a temperature probe and verify that the engine is not overheating.
2. Disconnect the tan temperature wire from the pack and retest. If the engine now performs properly, replace the
temperature switch.
3. Make sure the tan temperature switch wire is not located next to a spark plug wire.

Simply test also hook four of these in line and run the engine gives you a CLEAR visual if you firing intermittently or not during the symptoms
http://www.harborfreight.com/cpi/cta...temnumber=4424

[tsubaki]

Thanks ny.
No indications of overheating or oil deprivation from sensors or the like.
This is an intermittent pause of engine rpms much like loosing fuel very quickly or an ignition breakdown, but only after completely warmed up. No dropping to low rpms as if overheating or low oil like the SLOW system was intended.

[THEFERMANATOR]

60 degree loopers didn't have many powerpack problems with them, but the optical sensor is known to cause issues. Also be certain to get the cover back on the flywheel for the optic sensor as any light WILL cause false readings in it. It's also not a good idea to run these engines with the cowling off due to the optic sensor getting falso readings from light that gets under the cover. Do you have a PRV meter? If so I would check the stator when it is acting up. Also get you a timing light and make sure to mark the flywheel for TDC on each cylinder on it. When it acts up take your test light and connect it to each wire and see which one is losing spark or jumping time. If it is all of them I would say it is the optic sensor.

[tsubaki]

THANKS Ferm!
I'm assuming the optic sensor is the crank position sensor (gotta help me out here, if not, let me know).
Only 1 run was attempted without the cowl on, the transducer sprayed water, that defeated that. Haven't removed the cover to the sensor over the flywheel (waiting for the part to arrive).
How in the Devil is it light impulsed?? I figured it would be magnetic.
And what in the world is a PRV meter, man, I've been out of the loop a while!
Do have a timing light though!

We are about to the stage of just replacing parts till it stops acting up.

[THEFERMANATOR]

Yep the crank sensor is an optical style instead of magnetic like older engines were. It reads a light signal which has deviation across the RPM range than magnetic sensor's do. PRV= peak reading volt meter. You need one to properly diagnose a magneto as they produce large power spikes and you want to read the highest part of the peak.

[tsubaki]

Thanks FERM!

[tsubaki]

Well, just to update.
After about a week of the parts shop ordering the sensor from two different locations, it arrived.
While installing the sensor, it was obvious that someone else had done the same thing but had damaged the timing wheel and just bolted it back in place.
Ordered that part today, we'll see if that was the whole problem when it arrives.