Re: Correct control for a 1960 Merc
tmor51,
Battery CD ignition is the family of ignitions that followed the magneto. They began production on Mercs in the latter 1960s. The teardrop box that was correct for your 1960 Merc400 is no different than the square white box without tach connector or the square white box with tach connector. All were for magneto Mercs. So if you really want to find a used harness and box you can look for any of those white boxes with your plug type. Due to their age, it's hard to find good used ones still around, but if they've been kept inside, good ones can still be found. I've got at least one of each type, not good enough to sell, but good enough to use around the shop. The black dual-lever box that someone showed a pic of on the fiberglassics board is also correct for your motor but those are getting hard to find.
In order to assure yourself that you wont damage your 1960 Merc400 magneto, you can easily find out for sure if 12 volts is ever getting to the mag from your harness. Its very easy. There wont be any other issues with the other pins of the harness.
The way a magneto works is to generate its own power, and it therefore needs no external power coming into it. The way a magneto motor is to be shutdown is by simply grounding out the magneto. If youre as old as I am then you will no doubt remember the early gas lawn mowers that used a small piece of metal on the engine block that could be pushed against the spark plug to ground it out to stop the motor. Well, that is exactly the same way your 1960 Merc400 is shut down. When the key is switched to the off position, that lead to the magneto is grounded so the sparking stops.
There is only one wire from the harness that goes to the magneto on your 1960 Merc400. You can remove this wire with a 3/8 or 7/16 nut from it's insulated connector. The wire you will disconnect from the mag will be connected to an insulated terminal at the side of the mag. There will also be a braded ground wire (with no insulation) connected to the back of the mag and this one stays as it is the ground wire for the magneto. There may be one additional wire going to the magneto on your motor. On some of those motors there was a mercury switch that is a small round cylinder about ½ in diameter and 1 - 2 long that is mounted onto the engine block at a 45-degree angle. This (optional) switch was there to cause the mag to be grounded when the motor hit something in the water and the prop came out of the water while still running. As the years went by, most of these mercury switches (if one was there in the first place) were disconnected or removed because they themselves sometimes went bad and caused the motor not to start. On a rebuilt motor, I would think you probay wouldnt have a mercury switch, but even if you do, that lead is okay and dont disconnect it. So, the only one wire you want to disconnect from the mag is the wire going to the middle of the side of the mag to the insulated terminal.
After removing that harness wire, you can then plug up your harness to your Merc400 (with the removed wire not touching the magneto or touching anything grounded), and test this disconnected wire with a standard 12-volt automotive test light. With the test light lead grounded to the block and the probe end of the test light connected into the harness wire (that you disconnected from the mag), you can move your key switch through all positions: OFF ON/RUN START OFF. Do this several times and be sure the test light has good connections and that your battery is connected. If that test light ever comes on, in any position of the key switch, then 12 volts is coming through that wire (a no-no for the magneto on your 1960 motor), and if this is the case, then your harness is still useable with your existing control box, but the key switch will just need to be re-wired. Before you do this test, be sure your test light is working by putting the probe end to the big red wire of the engine wire harness which should cause the test light to light up showing that you have a good ground with the aligator clip and that your test light is working properly. Then proceed to test the wire you disconnected from the mag by moving the key through all the possible positions.
So, if you do have 12 volts going to this mag wire, you can get the switch re-wired, and I can help you there too. I do this for fun and will be happy to help as much as I can. I love to see these old Mercs still going strong. If the disconnected wire does not have 12 volts going to it, then a double-check to make sure the harness is wired right is to check continuity (with a standard Radio Shack multimeter/ohmmeter) that this disconnected wire is grounded when the switch is in the OFF position and that it is not grounded in the START or ON/RUN positions. If the latter is the case, then you can plug up that harness and head for the water.
By doing these tests you can be assured that you will be doing all the up-front checking and not damaging your motor if the harness isnt wired correctly. As you continue, please feel free to email me at
mwinn@genesco.com and Ill get the emails quicker and Ill be happy to stay with you until youve got this motor on the water.
Best of luck with it,
Marty
