1987 25 hp Merc no spark - shorting out

[ShadowGrass]

Hi:

I have an 87 25 hp Merc tiller that suddenly quit firing, I checked it and found no spark. While testing my helpful assistants (son and dad) noted that they were getting shocked while I was pulling it over until my fingers were raw. Of course I used them as a tester for several more pulls just for kicks.

I looked over the wiring without tearing anything apart and can't see any breaks/rubs. I am hoping someone can point out common short locations that I can visually inspect before testing the whole system. This motors too good to trash and too poor of condition to keep taking it to the shop.

I really appreciate the help.

Perry

 

[Mi duckdown]

Re: 1987 25 hp Merc no spark - shorting out

Need fuel

 

[ShadowGrass]

Re: 1987 25 hp Merc no spark - shorting out

Thanks for the reply. It is not a fuel issue it is a spark issue, there is zero spark at the plugs. I believe it is shorting out, because the people holding onto my boat were getting shocked when I pulled it over. They were in a boat in the water holding onto the side of my boat ... My boat was on a lift. They were the best path to ground.

 

[oldman570]

Re: 1987 25 hp Merc no spark - shorting out

You can test the stator and check ALL the ground connections to the block. Check the plug wires after dark to see if they are bad, and look for any arching around the switchbox and flywheel area. Could be the switchbox ground has gone bad and causing the trouble, if the stator test good. The coils themselves, or their ground could be bad, also if the relation were getting a real good jolt. You should always ground out the plug wires when testing with the plugs removed, as damage to the switchbox can happen very quickly other wise.JMO
Oldman570

 

[ShadowGrass]

Re: 1987 25 hp Merc no spark - shorting out

Thanks for the detailed response I will try to work through all of those items. They were getting shocked while the plugs were in and the wires were on.

Thanks again.

Perry

 

[MikDee]

Re: 1987 25 hp Merc no spark - shorting out

In a situation like this, I switch to resistor plugs! For some reason, it then sends all the spark to the plug tip,,, no more arcing, or shocking.