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Rectifier for 1975 Johnson EL75C

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flyingkraut

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My 1975 40 HP Johnson runs great, but doesn't charge the battery. I'm pretty sure that's due to a blown rectifier. Does anybody know where I can find the part, or will the rectifiers for 1984 and newer motors work?
 
flyingkraut said:
My 1975 40 HP Johnson runs great, but doesn't charge the battery. I'm pretty sure that's due to a blown rectifier. Does anybody know where I can find the part, or will the rectifiers for 1984 and newer motors work?
Click to expand...

The rectifier on that model is a four wire rectifier which would be located on the port side of the powerhead with its wires attached to a terminal strip.... rectifier #581778 . I have one left in stock. If you can't find the rectifier here, contact me via a PM.

(Small Rectifier Test)
(J. Reeves)


Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.


Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.


Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.


Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
Thank you Joe, I was hoping that 581-778 would work. It seems though that the new part has only yellow wires on the rectifier site, not the corresponding yellow/grey, yellow/blue & so on. Is there any difference in those 3 yellow wires on the rectifier side?
 
The later rectifiers came with only yellow wires, I failed to mention that. It makes no difference where you attach those yellow wires as long as they are attached to where the original yellow/stripe wires were connected, one to a terminal.
 
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