TOPIC: 1969/1970 Mercury 800 voltage drop

Greetings,
I just got a 1962 MFG Westfield with a 1969/1970 Mercury 800. The motor won't start and I was hoping it was something simple but I'm beginning to have doubts. I've never worked on outboards before but I have worked on motorcycles and cars.

Here is what's going on: turn the key to start, nothing happens, starter doesn't engage, no clicks, etc. While in the off position, when I check the engine voltage off the solenoid and switch box red terminal it reads 12 volts. While in the run position, the solenoid, switch box red terminal and white terminal all read 6 volts. I am thinking the switch box is shot..any thoughts? Thanks.

FYI, motor s/n is 2665614

P.s. in case anyone stumbles across it, I have a similiar thread open on another website's forum. Don't think I'm spamming, just trying to get my problem resolved quickly. Thanks again for any advice!

have you tried turning the engine over by hand ?
if that goes well I would try using the pull rope to stat it up . not a cure to your problem, but at least it might narrow down the issue

Thanks for the reply. The motor seemed pretty difficult to start by hand. I temporarily connected the starter to an alternate power source and it spun the motor but I had no spark (key was in the run position.)

Dont sweat it, your in the right place. The real "BRAINS" on this site will no doubt provide you with the correct course of action soon enough !! Good luck !

I could probably help if you can provide a wiring diagram and the exact voltages at each point you are testing. But I'll bet someone here knows what's going on with less info.

Make sure the battery is fully charged before testing.

Good luck,
Bill

Hi,
If I understand correctly and there is but 6 volts when the keyed ignition switch is on you would seem to have a fault in the switch or the wiring which reduces the voltage below the input required at the switchbox. If you wish to confirm that the fault does or does not lie with the switchbox itself, then you could wire the switchbox directly to a battery carefully. Ground the housing to the negative post, apply 12 volts to the red post and check the voltage matches the battery voltage, then apply 12 volts to the adjacent white terminal and again check the voltage to see if it returns to 6 volts or remains at battery voltage as it should. Original Mercury wiring, both inside the control and the engine cowl is almost certainly rotten, and a blown switchbox could easily result if not corrected before motor operation. Careful please.

Regards,
Joe
www.fergusonpoolemarine.com
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Thanks for the responses. Joe, you are basically saying if its not the switch box itself, it could be either a fault in the ignition switch or the white wire, right? How would it affect the voltage at the starter solenoid? I am going to try your test as soon as I can though. Running a new white or replacing an ignition switch is definitely more favorable than replacing the switch box.

For others reading, this is the wiring diagram I've been using:

www.maxrules.com/oldmercs/Wiring/1966ona/30.gif

I also have a 1970 Mercury 800 and am fixing rotten wire. I think Joe has you on the correct path. From what you wrote I would not yet suspect the switch box, switch or white wire. You seem to have a basic power problem. Before trying what Joe said I would do a little more basic meter work.

With the switch in run check your battery voltage. Check first on the terminals and then on the connectors. If you get 12V then check from the battery + to the red on the switch box. You should get less than a volt. More than that is rotten wire or corroded connection. If that is OK, check from battery - to engine ground. Again this should be less than a volt.

I am rather sure that one of those three reading will be way off.

Daniel

Thanks Daniel - yesterday I took apart the remote control box to test continuity in the ignition switch and the wires basically fell apart in my hand. Not sure if that was the only problem but its probably part of it. Good news is the switch is working fine.

Interestingly enough, it looks like someone had re-wired the switch at some point. The wires were soldered on in a pretty sloppy manner and were covered in liquid electrical tape.

Hi,
Just as I thought, I have seen far too many. We have the tachometer plug & harness for inside the MerControl. Do very carefully inspect the heavy battery cables to determine the usefulness of your (MerControl) harness. Many have too high of resistance in the battery cables and are rotten even to the molded rubber plug to allow the splicing-in of new wire. Although costly, a new harness is the best repair. This also is true of the motor's wiring harness and components which have their own wiring (stator, distributor housing, ignition coil, and mercury safety switch). All but the safety switch can be had in factory or aftermarket, but we strongly prefer the factory harnesses, and besides there is not a great deal of price differences either (please write if you would like a quote).
"a747freak" I did e-mail you my phone number if you have any questions. Writing a long message by phone takes too long for me to fully add all my thoughts.

Regards,
Joe
www.fergusonpoolemarine.com
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Joe, I performed your originally recommended test today by hooking the red and white terminals to the battery. Voltage looked good and so I used a jumper cable off the battery to get the starter spinning and check for spark. I am happy to report I got a killer zap by one of the plugs while checking, so it seems the problem really is just n the wiring. My next step before I get a new harness will be to try and get the motor running, so I will know if it needs more parts. Thanks to everyone for the help.