Depends on the engine and year.. they bolt them in all different places... with out knowing the engine.. best bet is to trace the wires coming from the stator.... stator leads will be yellow/black and yellow/red... tach wire will be grey.. rectifier will be a square or rectangular diode pack molded to a heat sink usually with three or four wires on it..including the grey tach "sender"...
Wow Joe, you're a better man than me. If I tried all that stuff I'd end up burning the boat to the waterline.
New TACH solved my problem.
Easiest thing I've had to replace on the boat yet....
Nice when things that should be working...are working.
Even better when a repair goes smoothly and successfully.
...it finally happened, there are no more secret spots