HAUNTED 1977 Mercury 850 4 cyl

Joined
Jun 1, 2010
Messages
18
Haunted 77 850........
My serial number is 4725418. This is the thunderbolt, with no distributor. I am having a couple problems with my engine. I have been reading posts for the last month and cant find ANYTHING like what im having. I am pretty sure it is my igniton switch but would like a second opinion. Here goes:
With my wire harness "disconected" from the engine, I am getting a power reading 1 volt on the (orange) kill wire with no power going to the engine! How is this even possible????? I disconnected the kill switch and removed the orange wire from switchbox. If I probe the orange wire from the switchbox and probe the other end that the harness plugs into, I am getting voltage. I probed all the other wires on the engine harness and none of the other ones have a power reading. I did notice over time, this reading will slowly drop. I guess it is discharging. Is it possible that the wire is so old, that it is holding a charge? I am 100% sure it is not touching a power source becaue there is'nt one. What I also noticed is that I am getting a very low positive reading on my boat ground wire to engine. I checked all the engine ground and they are good. I have already rewired the engine but not the boats harness. I beleive it could also be my battery since I am getting upto 18Volts at the soleniod and at the rectifier. I beleive it should be beween 12-16? Also, when cranking the engine, all four plugs have a "weak spark". When I check the coils, I am barely getting one volt. The engine wont start. I have already changed that stator (new cdi). All readings are good. I did try to disconnect the alternator wires with no diffrence. I am about to try and start it with the kill wire off to see if she will start. I will also be testing the trigger today. I have read that ANY kind of power reading on the kill wire can fry the system.
Also when igniton is turned on, it is getting power through the wires. The engine cranks good with the key, it will just not start.
Any help would be GREATLY appreciated!!!!! THANK YOU!!!!
P.S. Since I have a "weak spark" on all cylinders, that would indicate that the trigger and switchbox is good, correct? Weak spark = barely visible
 
Joined
Jun 1, 2010
Messages
18
Re: HAUNTED 1977 Mercury 850 4 cyl

Well, after disconecting the orange kill wire, she fired right up!!!!! This is after not being started for over two weeks. I am just sitting here wondering how many other people had this same problem and spent a $1000 "trying" to fix it. I went ahead and changed the stator because it was putting out low readings. If you are having hard starts, odds are it could be this wire or something in the harness. I set up my throttle advance to kill the engine once fully closed so this eliminates the kill switch all together!!!!! Looks like there will be swimming and fishing today!!! woo-hoo!!!!
I still cant figure out why or how the kill wire has current..... I checked it again after completely disconecting it and still has a .9 charge..... So weird.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,082
Re: HAUNTED 1977 Mercury 850 4 cyl

The ignition system is a Capacitive Discharge Ignition (CDI). Capacitors store electricty. That may be why you get a dimishing voltage reading.
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: HAUNTED 1977 Mercury 850 4 cyl

There should never be voltage on that kill wire 'cause it'll damage the switchbox.

Most likely you have a bad ign switch with "leaky" contacts that's bleeding voltage over to the kill switch line. I bet if you disconnect the kill wire from the ign switch you'll no longer have voltage on that wire.

HTH.............ed
 
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