93 Mariner 40 hp spark issue

[marinemike43]

This has two black and yellow wires See attached picture.

The black and yellow wire in the control box ,when connected by itself,(Below two yellow ones)the engine will run. (It runs to the stop toggel switch on the sterring handle

IF I hook up the other black and yellow wire,(Its looped)it runs through the mercury switch,the motor wont run.

I assume its a bad mercury switch)

Any thoughts would be helpful.

Thanks Mike