75743S 1977 75 hp rectifier results and why it will not shut off.

[1*jaybird]

a mechanic told me that the rectifier may be bad since I checked and tested switch, and wiring, and it is on its third powerpac (not all by me). Is this possible? I performed the test on rectifier with a digital elec volt meter tester. this is what I got. <br /> <br />yellow grey to ground 0<br />ground to yellow grey 67<br /><br />yellow to ground 0<br />ground to yellow 63<br /><br />red to ground 0<br />ground to red 0<br /><br />red to yellow 0<br />yellow to red 0<br /><br />red to yellow grey 0<br />yellow grey to red 0<br /><br />yellow to yellow grey 0<br />yellow grey to yellow 80<br /><br />I tested it and it shut off, tried it again and it shut off with the key switch again , like it is supposed to. I also cleaned the contacts even though they were not dirty. <br /><br />went on lake and ever since it hasnt shut off with the key switch anymore. what gives?? any help ? thanks.

 

[Joe Reeves]

Re: 75743S 1977 75 hp rectifier results and why it will not shut off.

That rectifier is faulty and requires replacing, however it has nothing to do with the ignition. Its purpose is to convert AC voltage coming from the stator to DC voltage in order to charge the battery.... nothing more.<br /><br />Note that the rectifier will not tolerate reverse polarity even for a fraction of a second so before you install a new one, check the polarity voltage at the terminal of the terminal block/strip where the RED wire of the rectifier will connect.<br /><br />Not shutting down with the key OFF..... The kill circuit is:<br /><br />1 - Black wire from powerpack to powerhead ground.<br /><br />2 - Black/yellow wire from powerpack to raised "M" terminal of ignition switch.<br /><br />3 - Black wire from the other "M" terminal of the ignition switch to ground.<br /><br />The two "M" terminals should be open with the key in the ON position, and closed when the key is in the OFF position.

 

[1*jaybird]

Re: 75743S 1977 75 hp rectifier results and why it will not shut off.

Joe, thank you for the great help. how do you know that the rectifier is bad from my tests? I will replace it, I have also realized that I have to charge the battery to top it off. I will check on the wiring. the switch tests all turned up fine. however, can a switch once in awhile work? It has shut off from time to time. usually about once every 20 tries, give or take each occurrence. thanks again.

 

[1*jaybird]

Re: 75743S 1977 75 hp rectifier results and why it will not shut off.

Joe, could you please clue me in as to why the rectifier is bad. what part of the test showed it to you. I forgot to tell you that the digital readout was only there for a second each time. then it would disappear. retest and it would show another reading, however it was close to the first result(s).<br /><br />I also found that the black/yellow wire was completely broke without any corrosion. it was at the area of where the whole wiring harness is entering the clamp at the engine. why would this one wire break and not the others in the same jacket. soldered it and rewrapped everything. thanks. glad that is done. Jason

 

[Joe Reeves]

Re: 75743S 1977 75 hp rectifier results and why it will not shut off.

The rectifier test is listed below. Possibly your meter is giving a false reading for some reason? Pick up a cheap $8.95 volt/ohm meter at Radio Shack or wherever and redo the test.<br /><br />(Small Rectifier Test)<br />(J. Reeves)<br /><br />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. <br /><br />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. <br /><br />Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires. <br /><br />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.