Merc does not encode the year into their serials (which is really just a production number) so that a dealer will never have "last years model" on the showroom floor.
Merc builds their motors in a "model run". For example, all the 6-25 horse models built between 1986 and 1994 were "mechanically identical" such that if a motor was built say in 1989 but didn't sell until 1992 it would have been sold as a "brand new" motor and the warranty would start from that date even though it was (technically) three years old already.
However, as stated, mechanically there would be no way to say that it wasn't "current".
I don't have a correlation between the production number and model.
In the portable line however, it's pretty easy to figure out.
M - manual or rope start
E - electric start
L - long shaft (20")
So an 8M would be a short shaft rope start and 8ML or 8EL would be a longshaft version with manual or electric start respectively. A "jet" would be a jet drive (impeller driven) lower unit as opposed to a (normal) propeller.
The "rectifier" system on Merc's is totally unregulated. The rectifier simply converts the AC voltage produced by the lighting/charge coils into DC.
So you generally get unregulated DC in the range of 13-16 volts. That is what makes it imperative that you use a marine (or rv, tractor etc - but not automotive) battery which, besides providing storage for the power, acts as a capacitor and regulator for the system.
While I am not an electrical (geek), two of the rectifiers posts take the AC feed from the charge coils. It basically (chops off) the positive and negative peaks of the AC and "rectifies" (splices) them into a single positive DC stream.
The rectified DC is then (available) from the third post.
If you decide to install a conventional marine tachometer, you can take the "signal" feed from either of the posts being fed by the charge coils.
The rectifier can not be used without a battery connected. It will burn itself out and possibly take out other components as well, if the power it rectifies has "nowhere to go".
Merc used to produce a regulator (discontinued now but still many laying around in "old stock" if you look hard enough) for the 25 horse and under "charge" system.
It could NOT be used to charge a battery but instead gave you a (roughly) 12.5 volt stable DC output, at varying amperage, which would allow you to power nav light (or other very small loads) WITHOUT having to carry a battery on board.
I run one myself (regulator) on a 15 horse model. At idle you barely get enough "juice" to get a dim glow from the nav lights, but at (cruise) speed or higher it is excellent for powering the lights.
