merc coil

this may be a dumb question, but how it the coil to be wired on a 51 Merc?? Ive been told that the car is grounded positive, so does the pos. side of the coil get wired to the distributor?? I know somone will have the answer!! Thanks in advance

 

You match the orientation of the battery. If the + cable is grounded on bat (stock), then the + side of coil is wired to points and - side goes to switch. And, if stock replacement, coils is a 6V unit that needs no external resistor.
For most purposes, ground doesn't matter...most circuits work either way, with only coil needing reversal. Radio may well be sensitive to ground, don't actually know, but not much else until you start adding in electronics.

 

thanks Bruce! I am going to rewire the car, and convert it to 12V. You mentioned the radio? I have purchased the "runtz" voltage drop dealies from Speedway motors, will these work for the radio, or will somthing else need to be done??

 

the runtz will only work for the gauges , and you need one for each gauge...oil pressure , coolant temp and fuel. they can only handle very low current so they will not work on a radio

doe a `51 merc have an amp gauge or a volt gauge? if it is an amp gauge the voltage will make no difference so one is not needed. if it is a volt gauge you can use a runtz on it , but since they are regulated to 6 volts you get no difference between charge and no charge. use a 60 ohm resister instead

 

The coil original to the car should have the tower (high voltage) terminal generate electrons to the spark plug (i.e. distributor) for best spark (lead pencil test).

One would hope the coils are designed thusly to accomplish this:
A 6V pos ground system coil should have the dist terminal be the + terminal.
A 12 volt neg ground system coil should have the dist terminal be the - terminal.

Due to the wiring inside a coil (the lower ends of the primary and HV secondary are tied together and go to the distributor points) , I don't think you can simply reverse the connections of a coil to accomplish what you want and get the best intended spark from the coil. Yes it will work but not efficiently.

If you are changing from 6V pos ground to 12V neg ground, I think you should change to a coil used in a 12V neg ground car.

Sounds like you already know that the starter will work on 12V neg ground with no changes.

 

the Merc does have an ammeter, so it should be fine! we had to "hotwire" the coil to get some juice to it...and run a byp*** wire to get the starter to turn...(hence the rewire job). She fires, but the old carb pukes gasoline all over the place! This old bou told me that rochester 2bbls bolt right up! Cheap carb too!! Any one know anyone to do the Radio work??