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Anyone have a blueprint for the Rectifier to a 4,5 hp (1976) Mercury Thunderbolt ignition system?

Richard Livijn

New member
I struggle with th eignition on my old engine... How can I repair/get a new rectifier to a 4,5 hp (1976) Mercury (it´s a Thunderbolt Ignition syst.)?
I have an old but it used to be very good Mercury 4,5 hp and last summer it died. I managed to buy used parts via ebay for the ignition system (rectifier)+coil.
I managed to get a spark yesterday, but I get really funny measurements from the rectifier and the maintenance handbook does not lead me right. However, I guess that the rectifier might be faulty. At least some of the diodes in the rectifier are faulty I conclude.
Since there are no new parts I have to rely on used or build new ones. I would like to replace the diodes but then I need a blueprint for how it is once made. Can you help me on that or any other good idea how to solve the problem?
 
That motor don't have a rectifier so I assume you mean the ignition module. Make sure the points are clean and wire to coil are not grounded..also check flywheel key.If it had spark and quit look for the simple faults first.
 
The module rarely goes bad look close at the insulator and wire going to the points if the insulator is cracked it needs replaced. The points trigger spark when they close opposite of the phelon mag ignition. Also look at the pigtail ground under the ignition coil it must make good contact to the bracket. You need a manual to check the diodes in the module and resistance of the ignition coil. It also has two different driver coils i believe CDI still makes the set?
 
Hi,
I sure has or must have ?! Everything is molded together witj plstics if you look on the bottom of the ignition module. Therefore you cant see the diodes...If you follow the instructions in the repair manual current one way is supposed to be blocked but not the other so there must be a rectifier...Anyway, this plate (ignition module) is hard to find and hard to repair..
 
Thanks!
I have replaced all the wiring with new ones and it is now in good shape. The pigtail is also ok. The small switch under te flywheel that opens and closes the ignition is slightly worn out, but works. The values for resistance etc given in the repair manual must be wrong since I can´s get these values on either of the two ignition modules I have. They are however used... The old coil is replacesd with another used one and it worked and if ou measure it it seems ok, but I´m really not an expert. My neighbour had a multimeter and we checked yesterday together. He could determin that the original coil is faulty. We struggled with the ignition module and got funny values on both: not the same at all and absolutely not as it says in the repair manual.
Since the ignition module is a rare thing I´m in to taking out the epoxy in it and put in new diodes, but I don´t know which ones really. Would be great to have a blueprint...
 
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