Possible electrical problem?

[humbleperchjerker]

I apologize in advance for this lengthy post, but have become frustrated with this problem as described below and I felt details were important to a suggestion or solution.
I own a 1984 Johnson 115HP electric start with T & T on a 1984 Ranger b*** boat. Late last year I experienced a blown fuse (the 1” 20 amp on the port side of the engine). I had been running and stopped and turned off the key switch to fish. When I attempted to restart, nothing! Had not experienced anything like this before and it took me a while to find the blown fuse. On my first trip this year, the same thing happened.
I took the rig to a service shop specializing in OMC and explained the problem. They suspected the key switch and installed a new one. They also installed a new power pack on the starboard side saying it was not operating properly.
I immediately took the rig to the lake and discovered the same problem (turn off the key switch and the fuse would blow, kill the motor without turning off the key and it would not blow).
Went back to the shop and they installed a new wiring harness. This solved the blowing fuse problem, but a new problem appeared. On the second trip out (the first trip was a tournament where everything operated correctly), after running to a couple of spots with no issue, the motor began to cut in and out from full power to what seemed like half power. It would cycle back and forth about 3 seconds apart.
Back to the shop! They could not recreate the problem, but gave me another power pack to install on the port side if the problem continued. It did, so I installed the new power pack and everything seemed fine.
I spent four days at a lake and had zero problems. Yesterday (one week later) I went to the lake and made the first two stops without an issue. Then the cutting in and out started again???? With a new wiring harness and two new power packs, I am at a loss as to what could be causing this problem and why it appears to be resolved only to return for no apparent reason.
Can anyone help???

[Solarman]

Might test your rectifier/ regulator, it adjust the voltage for your motor and may be spiking, throwing higher voltages at times. While having that tested, ask them to test output on magneto. Generally the regulator controls the voltage output, but the magneto produces the voltage. The rectifier converts it from AC to DC, and the regulator sends the required voltage to the system, and battery. Have tested, and see if spiking even when turning key off.

These are a couple items that could be causing this kind of problem. Can't think of anything else right now.

Don't worry about lengthy posts, with good details comes better diagnostics. And, the batteries in my crystal ball are shot right now. So, much better to explain any problems as well as possible. Thnx.

Good luck, post back when able if they find anything.

[humbleperchjerker]

Thanks Solarman. I will do exactly that tomorrow.

Appreciate your help/input.

HPJ

[duhranged]

Possible bad plug wire(s)??

[Solarman]

Plug wires (spark plugs) may cause a skipping when running, but don't think it could cause fuse to blow, unless shorting to another wire, and yes that could cause spikes and damage other electrical items.

Let us know what you find, good luck.

[humbleperchjerker]

Malfunctioning VRO pump?? This is the diagnosis from the shop. They had replaced while searching for the cause of the blown fuse problem. Since, I had been getting a 'no oil flow' warning when idling, but immediately went away when throttle was applied. They replaced again and motor ran fine during yesterday's shake down run. Does this seem logical? Can't get my mind around the "run WOT for 3 seconds, then run like 2 cylinders for 3 seconds....continuous this way for miles"????

Thanks