1990 Johnson 140 S.L.O.W

Hello all, new to the thread and could use some advice with an issue on a friend's 1990 Johnson 140hp. My friend states that he was returning from a day of fishing when the engine starting running rough and when he retarded the throttle below 2500rpm the engine ran normally. No alarms noted but every time he advanced the throttle the engine appeared to go into SLOW. He took the engine to a local mechanic and he was not able to determine the cause. This is where I got the boat. The VRO has been bypassed and he premixes gas/oil. I did the basic troubleshooting (compression, checking wiring, fuel system). I put the boat in the water and have determined that it is definitely going into SLOW. I disconnected the temp sensors one at a time and them left them both disconnected. Still went into SLOW. I ensured the VRO plugs were disconnected and stowed. The engine runs great right up to the 2500rpm threshold. Everything is pointing to the power pack. If any of you have other thoughts please feel free to share. Thanks in advance for your help.

I vote for the power pack too.

Is the vro harness plugged in?

Thanks for the input. Going to do a bit more checking but I am pretty sure that's the issue.

Thanks for the reply flyingscott. The harness is unplugged.

What did you ever find ????

Boobie said:

What did you ever find ????

Click to expand...

Hey Boobie, the owner went out of town for a few days and I,am waiting to talk to him. If he says go ahead I will probably order a power pack from CDI. Do you have any other thoughts? The stator ohms out fine.

Hello all. Here is an update. A new power pack did not correct the issue. The engine is still going into SLOW. After installing the new pack I went through the field testing again with the same results. With one and then both temp sensors unplugged and ensuring the VRO harness was unplugged the issue still exsists. I then put a timing light on each plug wire and spark was present on all cylinders. I am running out of ideas here. Any suggestions where I should look next? Could the diode in the harness be causing this problem? Help?

I discovered what is causing the issue. The warning horn shorted and melted inside control box. New horn on order. I will update when the horn gets installed.