Mercury 850 starting problem

[katsandsuds]

I have a 75 model merc 850 (ser #4297882) that has an intermitant starting problem. When I turn the key or push in for choke, nothing happens in either mode. If I turn the key over several times, it will begin working again correctly, but the problem has gotten worse since the condition began last time out. I have pulled the controls apart to verify the Neutral interlock switch is adjusted and working properly and it is. I have pulled the man-overboard safety switch (not sure proper name) gnd off to make sure that was not the problem, and I don't have, or can't find, a mercury tilt safety switch off the distributor side of the switch box that is shown in the wiring diagram. The controls are not original, one on the boat now is PN 881170A3, and inside the controls, the wires have different colors from the original wiring diagram so it is making it more difficult to troubleshoot.

I believe the switch is going bad is the problem, but not sure. My questions are:

Is there anything other then the key switch that links the starter solenoid ckt and the choke solenoid ckt and could cause both ckt's to be disabled at the same time? The wiring diagram says there is not, but would like to check with you guys, not sure if there is any type of interlocks or not that is not obvious on the diagram. I have checked the Internal to External harness connector and it is spotless. If there is nothing else linking them together other then the switch and the plug, then it has to be the switch. Also, with the lever out of neutral, the choke should still work, just not the starter ckt.

Secondly, does anyone have a wiring diagram for the controls themselves so I can make sure I understand the color coding in the new controls.

Thanks in advance for your help.

 

[Chris1956]

Re: Mercury 850 starting problem

I am not sure what control you have, but if it is a Mercury, I would think the function is the same as the original control with the motor.

The choke should work whenever the ign key is in the run position. The neutral safety switch in the control is the only switch of it's kind in the circuit. There is no safety switch on the motor. The mercury switch would be on the port side of the switchbox. The are usually blue plastic and look like a standard condenser.

Your choke wire grey on the motor. Ign accessory (+12VDC) is white. Starter solenoid is yellow. On the control, depending on the year. Purple wire is ign accessory. Starter solenoid is yellow/red, choke is black/white? (I am not really shere about this color, sorry)

BTW - it does sound like a bad ign switch. Can you disconnect the power to the motor, spray some Wd-40 into the switch and exercize it a lot?

 

[katsandsuds]

Re: Mercury 850 starting problem

Thanks Chris. I am almost positive that it is the switch, just want to be sure. The controls are $200 so I think I will try to find a suitable switch and wire it in myself first. It is a sealed, waterproof switch so I can't spray it out.

 

[Chris1956]

Re: Mercury 850 starting problem

Mercury used to sell replaceemnt switches. They were the solder on type, and they fit the spot inside the control. I am not sure what kind you need.