Re: 1987 mariner 150 rectifierok, I've had a look at the photo. Focus isn't too good and it's a bit close. Any chance of another photo? I think it's a regulator. Is it on the back of the engine or the side? I really need the serial number from your engine.
Rectifier Circuit Design
Ac To Dc Rectifier Circuit
Year isn't too helpful with Mercs. The serial number should be on a plate on the side of the swivel bracket (that's the bit that tilts up and down), you can also find it on the powerhead somewhere.
Serial Number Perspective Rectifier Circuits
Either on a aluminium disc, like a core plug, or punched into the top of the block.