1986 Mercury 115 rectifier question

[quinones88210]

we recently purchased a 1986 Mercury 115 I-6 and were having problems running in water. It would run in the driveway just fine but once put in the lake it would die out once we went to accelerate out of the no wake zone. We got back and started running thru it and found out that we were only firing on every other cylinder. We started going thru everything and checking
wires and connections and so on and so forth, and we had came across a forum that mentioned something about the rectifier. So we started messing with that, and in con-clusion...when the rectifier is bolted to the motor like it is supposed to be the 3 cylinders do not fire, however when we unbolt it and just let it hang there the cylinders fire. We have only been in the boating world for a few weeks now and this has boggled our minds. If any body has any ideas before we just start sinking money into this thing trying to trace the problem it would be greatly appreciated. Thank you all for your time.

 

[Chris1956]

Re: 1986 Mercury 115 rectifier question

That motor looks to have a simple bridge rectifier. Disconnect the wires and tape them up. If the spark returns to all 6 cyinder, replace the rectifier.

Of course it would be better to test the rectifier with an ohmmeter, and be sure.

 

[quinones88210]

Re: 1986 Mercury 115 rectifier question

not sure exactly what style of rectifier it is, however i do know that there is 3 post on it. two of the wires both go back to the stator and then there is a terminal marked positive and that wire goes straight to the solenoid. We picked this motor up for 1,000 bucks and the wiring has been a nightmare. but from what i describe does that sound correct? i have ordered a repair manual for this engine but am about a week out on recieving it, just trying to get a head start if possible. thanks so much for your help.

 

[Jeff_G]

Re: 1986 Mercury 115 rectifier question

Do as Chris suggested.
However I think your wiring is still screwy. The rectifier is a separate system from the ignition system.

 

[Chris1956]

Re: 1986 Mercury 115 rectifier question

Jeff, On those ADI ignitions the stator coil for charging shares a common iron core with the stator ignition coil. if a rectifier diode was to short to ground, it could affect the amount of voltage the stator ignition coil could produce, possibly reducing the voltage to the switchbox below a threshold. I have never had first hand experience with this, but have heard that it is true. Of course I would simply test the rectifier and replace it if necessary.

 

[j_martin]

Re: 1986 Mercury 115 rectifier question

Jeff, On those ADI ignitions the stator coil for charging shares a common iron core with the stator ignition coil. if a rectifier diode was to short to ground, it could affect the amount of voltage the stator ignition coil could produce, possibly reducing the voltage to the switchbox below a threshold. I have never had first hand experience with this, but have heard that it is true. Of course I would simply test the rectifier and replace it if necessary.

I agree. You will find that the rectifier is shorted to ground.

That said, a manual, a meter, and following a relatively simple maintenance procedure would have led you here in minutes, instead of days.

hope it helps
John