1978 Mercury 500 50 hp No Spark

[eg196]

I recently bought my first boat and outboard. I ran the motor a couple times for a few miles, but the wiring needed to be redone. So as i set about to rewire it, one of the wires from the second to the top post of the switch box made contact with and sparked on the positive for the starter. Now I am not getting spark. Is there a procedure on testing things for no spark? I have a multimeter and know how to use it. is there any way to test the switch box? the only post that reads voltage on the switch box when cranking over(electric start) is the top on, it reads 16~ volts, if that helps. I would really appreciate any help or suggestions, Thanks

 

[Mercurylips]

I will not be much help electronically, but I have essentially the same motor. Sounds to me like the switchbox is gone. I have done extensive rewiring on mine and always take the battery out of service before working on it. Only takes a very slight touch to the wrong spot and box can be toast. A new one is available here.

 

[eg196]

yeah it was a stupid mistake. so is there no way to know for sure before i spend the money? and is it absolutely impossible to fix the current box?

 

[Mercurylips]

Fixing the current box is way beyond my paygrade. (I don't think that is an option) As far as testing, you are way ahead since you have a multi-meter. I really hope someone that knows where to start besides just standing back and throwing money at it, will chime in. I do know that a bad trigger and/or a bad stator can also damage a switch box. Have you done a compression check yet.

 

[merc850]

Are you sure it's a 1978? Here's the wiring for a 1978 which is different than a 1975. Which post did you touch?

 

[merc850]

doh.

 

[eg196]

This is what mine looks like http://www.maxrules.com/oldmercs/Wiring/1966ona/26A.jpg

 

[merc850]

Well that makes it a 1975 or earlier - a serial Nr. would help - here are the test values