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  1. #1
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    Default Tachometer hook-up for '69 Evinrude 85Hp

    I've read in other posts that the grey (send) wire for the tachometer should be hooked to the yellow/grey wire at the rectifier/terminal block. Where exactly is the rectifier and what does it look like?

    Thanks for the help.

    Mike
    Mike

  2. #2
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    There should be a gray wire leading from the forward end of the instrument wiring harness that would attach to the "S" (sensor) terminal of the tachometer. However, the answer to your question follows.

    (Small Rectifier Description & Location)
    (J. Reeves)

    On most 2,3,4,6 cylinder engines, the small rectifier is located on the starboard (right) side of the engine just in front of the engines electrical wiring strip. There are a few older V4 engines that have the wiring strip on the rear portion of the engine and the rectifier would be located just under that terminal strip. The smaller horsepower engines usually have the rectifier located on the starboard side of the powerhead close to the carburetor area.

    The rectifier appears to be a round object approximately one inch (1") in diameter and also about one inch (1") high. The base of it is sort of triangular in appearance and is attached to the engine with two (2) screws/bolts..... usually one screw/bolt is larger than the other. The rectifier, depending on which one your engine uses, will have either:

    One Red wire, one Yellow wire, and one Yellow/Gray wire, or One Red wire, and two Yellow wires.

    Note that either of the above rectifiers could have a fourth wire which would be Yellow/Blue

  3. #3
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    Thank you Joe.
    Mike

  4. #4
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    Hey Joe,
    I hooked up the tachometer to the amplifier, (rectifier is bad, ordering one asap!)and took the boat for a test run. Motor would only tach to about 2500 rpm and after 15 minutes of idle speed quit altogether. Is the bad rectifier likely to have caused this behavior?

    Thanks,
    Mike

  5. #5
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    Could be a bad rectifier OR a bad tachometer.

    Assuming that the engine is hitting the proper rpm but the tach isn't reading properly.

    First thing to do is to check the rectifier as follows....

    (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.

  6. #6
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    In the first place, in 1969 those motors were wired for a special tachometer that got its signal from the amplifier. Those special tachs are obsolete now. But the new alternator tachs will work just fine,,,IF you change the wiring at the motor to get a signal from the alternator. That is done by connecting the grey wire to the yellow/grey wire from the rectifier. You make the connection at the terminal strip.

    So, you connected yours to the amplifier huh? Shoulda followed the instructions. I don't know if it damaged the amplifier or not. Maybe. You did say it quit running.

  7. #7
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    F_R,
    I did hook the tach to the yellow/grey wire at the terminal strip and got no signal. Then, I hooked up to the amplifier at the terminal strip to make sure the tach worked correctly. Tach works, appears that the rectifier is bad but will verify tomorrow by testing per Joe's instructions. Question still stands - would a bad rectifier cause this behavior or am I looking at two separate problems?

    Thanks,
    Mike

  8. #8
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    Yes a bad rectifier will definatley cause your problems.

  9. #9
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    The ignition system (amplifier) gets its power from the battery. Unless the battery is severely discharged, the motor will continue to run with a bad rectifier--or even no rectifier. The rectifier's sole purpose in life is to change AC to DC for charging the battery. Has nothing to do with the ignition system other than keeping the battery charged.

  10. #10
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    F_R..... Your post #6 above..... I had completly forgotten about those old tachometers that hooked up to the amplifier. Wonder which tachometer is involved here.

    Capt_Mike..... If you have the later model tachometer which will operate off of the rectifier, it should have a dial on the back of it which you would set to number six.

  11. #11
    Lieutenant Commander Lion hunter's Avatar
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    FR and Joe are correct that a modern tach will not register correct off the coil. I just hooked up my tach on a 69 60hp and the setup should be similar to yours. My rectifier had 2 yellow and one red wires. I tapped into one of the yellow wires and it worked correctly. My Faria tach had 6 setting on the back:

    Poles/Pulses -- Setting
    4 - 1
    6 - 2
    8 - 3
    10 - 4
    12 - 5

    I set mine to #5 12 poles/pulses. The #6 six setting on mine according to Faria is for diesel motors.
    The Crestliner Restoration

    http://forums.iboats.com/showthread....49#post2218249

    1967 16' Crestliner and 60hp Johnny

    Klamath Trailorboat and 9.9 Johnny

  12. #12
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    Just checked the rectifier per Joe's excellent instructions and it indeed tests bad. Just ordered a replacement. I do have a new teleflex tach set to 6P per instructions. When I hooked up the charger to the battery it showed the battery 75% discharged. I would guess that the motor should have still run at that level so I'm charging the battery in preparation for searching out why it quit running. It sounded like it was not getting fuel so I'll start there.

    Thanks for the help.
    Mike

  13. #13
    Supreme Mariner Joe Reeves's Avatar
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    That Battery Capacitance Discharge ignition (pulsepack operates off of battery voltage) demand a top notch battery, fully charged, with a rating of at least 70 amp hours. Anyhing less can damage the pulsepack.

  14. #14
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    Default Re: Tachometer hook-up for '69 Evinrude 85Hp

    How can I tell if the pulsepack is damaged? BTW all, never trust the fuel guage. She quit because she was out of fuel
    Mike

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