200 20hp 1978 rectifier needed

Does anyone have a spare rectifier for the light/battery charging system they don't want? The one I have on my engine only has two contacts which are connected both to the coil and the external plug connector on the front of the outboard which give an output of AC current. But I need DC 12/14 volts for the battery/light system.
The lighting coils give out a peek total of 19 to 21 volts AC ( when disconnected from the rectifier) but when connected give a reading of only 10 volts AC so I am thinking that it isn't a rectifier fitted to the engine but a resister which reduces and stabilises the AC output. I am still confused as to why it is only 10 volts and not 12/14. if anyone can set any light on this I would sure appreciate it.
Kindest regards,
Eric

at what rpm are you taking the readings?i am not familiar with that motor but a rectifier only will not filter down to a flat line dc..is you put the meter on dc volts what do you read?

The AC voltage on tick over is about 10 volts (when rectifier is connected or disconnected) when I rev up it jumps to 19/21 volts AC (rectifier disconnected) but when connected stays at 10 volts AC. even when I rev the engine.. There is no reading at all when I change my meter to DC. The same two wires from the coils are joined onto the same wires to the plug but both sets are connected to the terminals on the rectifier. All rectifiers I have come across have at least three connectors, some using the casing as an earth, two connectors are the AC input and the third (usually red) is the + pos to battery and the case being the - Neg. With only two connectors on the unit made me think that is a resister or a voltage stabiliser but AC ...

can you post a pic of the resistor or rectifier?

I can in the morning as I am not near the engine today.

Can't seem to add the photo ??? on front side there are just two terminals rectangular casing. the other side has 75075 stamped into it. Don't know if this helps...