Mercury 500 no spark

[Nandy]

Mercury 500 / 50 H.P. Four Cylinders<br />Motor s/n 2479050 Year prob. 1968<br />Here I go, working motor and I have to try to make it work better, Right???? Well, I found that the cables jackets of the internal harnes for this motor are comming appart. This was causing me problems trying to start the problem as it was short the starting cable. I disconnected the harner but forgot to take the secondary cables I had for the bateries. That meant that some cables where still alive. One of those cables touched the orange cable that goes to the blue connector in the switch box. Now I have no spark on the plugs.<br />I tested the distributor coils and the resistance is ok. However the book does not shows how to test the switch box. I check them and only the blue terminal is grounded. There is no continuity beetween any other terminal. Can anybody check if their working motor also shows the blue terminal grounded? I really doubt that will be the case, this terminal is grounded to shut off the motor. <br />Anybody has a cheap used switch box for sale?<br />Thanks...

 

[Nandy]

Re: Mercury 500 no spark

The dealer from where I get the parts from does not have the equipment to check my switch box. Does anybody knows a place in the Carolinas that can do this? Also a name or number for a marina "junk yard" will become handy...<br />Thanks

 

[Nandy]

Re: Mercury 500 no spark

Does anybody has a diagram of what is supposed to be inside of this switch box? I wonder if it would be possible for me to fix it.

 

[Chris1956]

Re: Mercury 500 no spark

Nandy, Those switch boxes are usually "potted" components, that is all the components and the connectors are covered in epoxy. This is obviously difficult to repair. I have attached a switchbox test courtesy of "Clams Canino". It may assist you in troubleshooting. Good luck!<br /><br />I think this is what you need, pretty sure Clams has posted this here before so I wanted to give him his due credit;<br /><br />MERCURY BATTERY-POWERED CDI TEST <br />FOR DISTRIBUTOR MODELS<br /><br />This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.<br /><br />This test assumes your coil is good (most all are).<br /><br />DISCONNCT BATTERY <br /><br />1. Turn off ignion<br />2. Disconnect all 3 wires on the distributor side of the switchbox.<br />3. Remove the HV lead from the coil to the center cap (remember it unscrews<br />from cap)<br />4. Reconnect that HV center lead to the COIL side only.<br />5. Position that HV lead about about 3/8" from ground (block, shrouds etc)<br />and find a way to hold it there.<br />6. Jumber the brown and white terminals on the dist. side of the switchbox<br />together.<br /><br />RECONNECT BATTERRY<br /><br />7. Check that you have +12 V at red terminal.<br />8. Turn on ignition and verify +12V at white terminal (on red terminal side)<br />9. Touch the black terminal to ground - unit should cause spark each time<br />you touch ground.<br /><br />If that passes and it won't fire at all, suspect the trigger

 

[Nandy]

Re: Mercury 500 no spark

The switch box is covered with a ruber like material. I have been cutting this material away to get to the componets. The problem I am having now is that the ruber like material is mixed with some little rocks, looks like the material used on boxed items in order to keep it dry. It is a very slow process, wonder what I will find.

 

[luv fishing]

Re: Mercury 500 no spark

try this disconect batery leads unbolt the rectifier from motor caseing make sure its not grounded try cranking and check for fire.i just did the same thing to mine today. mine is running fine.now you need to check stator and see if charging.then replace rectifier.

 

[niggered]

Re: Mercury 500 no spark

I have the same year Mercury with the same problem. No Spark???<br /><br />I need assistance in basic Repair for Dummies!