switch boxes

[Ranger335V]

After going wide open for a short distance(200 or 300yrds.), my motor will stall-out, and die if I don't back out of it.
I've had this problem before, about ten years ago. It cost me $700 to get fix. It turned out to be the switch boxes.
Is there an easy way to check these to see if they are the problem again?

I have an 84 Mercury 115hp. Is this a problem with this motor? or Is there something causing this?

[boats.net]

You would need a peak reading voltmeter and test output voltage and bias voltage are within specs in service manual to find failed part.