Johnson 90hp rectifier help

[adominique0313]

Ok he is my question 2003 Johnson 90HP (J90PLSTC) is on a 2003 Crestliner Superhawk
1) What does the rectifier do? I understand that it makes DC into AC but why would you want to do that on a boat?
2) There is a wire coming from it, that is yellow/grey in color. Any Idea on where it goes it has been cut off. I measured it with a fluke meter in DC and it read 6.9 volts (didn't realize it was a rectifier when I measured it).
3) The boat had this thing in it that has the name GUEST on it (one of the 3 studs is broken off. I looked it up online and said it is an electrical isolator. It went to both batteries it also has A, 1, 2 written at each stud, I have a feeling the yellow/grey wire went to the A on that.
Thanks for any help

 

[Fed]

Rectifier changes AC into DC.
Yellow/grey is for the tacho and should be contained in the engine wiring / harness and not connected to the GUEST switch.

The GUEST switch is for 2 batteries connected to 1 motor.
Batt1, Batt2 or BOTH which is probably A for ALL on your switch.
Usually they are 1, 2, BOTH & OFF.
Hope this helps.

 

[adominique0313]

Rectifier changes AC into DC.
Yellow/grey is for the tacho and should be contained in the engine wiring / harness and not connected to the GUEST switch.

The GUEST switch is for 2 batteries connected to 1 motor.
Batt1, Batt2 or BOTH which is probably A for ALL on your switch.
Usually they are 1, 2, BOTH & OFF.
Hope this helps.

Thanks for the quick reply
I will have to dig further into the harness I have the yellow/grey coming off the motor and goes thru to the battery compartment but nothing from there forward
my uncle hooked it to the + on the battery hope this didn't screw anything up!!!