1992 johnson 150 won't run at WOT

[Jasonlane618]

I have a 1992 johnson 150 60 degree with ois ignition
That wont run at WOT or plane the the boat out and it seems to have weak intermitted spark on the port side bank
I have a running motor to swap parts from and switched the stator ,optical eye , flywheel, cdi/powerpak, and shift switch with no change in runability
Seems like S.L.O.W. mode but not 100% sure
Any advice or tests to perform would be greatly appreciated as I have been working on it for 2 weeks with no success
Thanks in advance

 

[Chris1956]

Well, you can disconnect the SLOW system, as well as the shift interrupt switch. To do that unplug both temp sensors at the heard. Unplug the shift interrupt switch, near the shift cable. There are a couple of diodes in the wiring for the alarm system, as well as the shift interrupt switch.

It makes sense to disconnect the black/yellow wire at the ign switch. Also, look for melted wires in the motor wiring harness. These can partially short the black/yellow ign killer wire.

 

[Jasonlane618]

Well I pulled the ignition switch and found melted ground wires not sure why the ground would be melted unless it's shorted to a power wire ?

 

[Jasonlane618]

One question is there suppose to be b+ on the blk/ylw wire I also see there is a diode in that circuit

 

[Chris1956]

Ground wires would melt if shorted to a power wire. I found melted wires at the trim gauge, and the plugs on the side of the engine. Not sure if you have exactly the same harness as my '98 Johnny 150.

Not sure if B+ should be on black/yellow. Probably no voltage when ign is off. When cranking, B+ is supplied to powerpack. After motor starts, only stator power is supplied to powerpack I would expect stator power to be AC, but is likely rectified and stored in capacitor in powerpack.

Diode near shift interrupt switch allows ign switch to ground both black/yellow and black/orange wires. Shift switch grounds only 1/2 the powerpack.