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1988 Johnson "88" Tach Question

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  • 1988 Johnson "88" Tach Question

    Howdy folks. I recently bought an 88 Startcraft with the original Johnson 88 on it. The motor is in good shape, but has a bad starter. I have a new starter on order, and expect it in a couple days.

    Leading up to the arrival of the starter, I have been cleaning up electrical on the boat. Previous owners hacked it up pretty bad, but didn't touch the OEM wiring for the motor. One thing I noticed is that the OEM (OMC) digital tach does not light up at all when the key is turned on. Is this supposed to light up when the key is turned to the "on" position? With a bad starter I haven't been able to run the motor and test the tach during engine run.

    If, in fact, the tach is supposed to light up with the ignition turned on then I will check voltages and whatnot. If I find voltages correct then I would assume the tach is bad. If it is bad, I will have to replace it with an aftermarket one I'm sure. Does anyone know if I can use any brand of aftermarket tach? I am looking at rebuilding the whole helm station, all gauges and switches. I'd like to get matching gauges of the same manufacturer and series (looking at the Faria Coral Series).

    Thanks for any information/help!
    My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

  • #2
    I would answer that with a no, it does not turn on the instrument light with just with ignition power if there is a instrument light circuit tied to the navigation lights.

    I believe this is common design for most if not all boat dash instrument gauges that are lighted.

    Quick way to find out is turning on/off navigation lights. First when no ignition power, second when motor is running.

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    • #3
      Before deeming the tach bad, what about changing the bulb inside?

      I do know on all my gauges, a few years old now, they have a separate wire just for the light circuit. Check and see before trashing your tach, especially if it works otherwise. Just a thought!
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      • #4
        The tachometer light (bulb) has nothing to do with the tachometer's actual operation.
        The bulb may be bad.
        The wire leading to the bulb (usually blue) would need to be connected to the "A" (accessory) terminal of the ignition switch in order to obtain 12v when the key is turned to "ON".

        However, the tachometer "needle" should peg backwards to the zero rpm position when the key is turned to "ON"
        Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

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        • #5
          curious -- Is the starter dead? Might try jumping from a vehicle just to see if it has some life (pos. clamp to post on side of starter, neg. to mounting base). It could simply be a wiring issue in the starter circuit, or corrosion at the battery connections.

          If the starter is slow, disassembling for cleaning my be the solution. In doing so, you might also replace the brushes.

          Is there anything lighting up at the helm? Starting at the fully charged battery, all connections need to be sandpapered shiny.

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          • #6
            Hey guys, I apologize, I should not have used the term “light up”. My question has nothing to do with backlighting. Rather, the tach is digital, and no digits show when the key is turned to the “on” position.

            The starter is bad due to the bendix sticking and the starter gear being destroyed. The starter does spin, but just grinds against the flywheel because it’s teeth (starter gear) are all chewed off.
            My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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            • #7
              Ouch. Can you turn the flywheel clockwise by hand with the engine in neutral?

              (can always replace the bendix, giving yourself a spare starter)

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              • #8
                Originally posted by oldboat1 View Post
                Ouch. Can you turn the flywheel clockwise by hand with the engine in neutral?

                (can always replace the bendix, giving yourself a spare starter)
                Yes, I can turn the flywheel by hand. The PO has been beating the starter to death over the last few years... I think a whole new starter is more than justified. I just got the new one delivered today, it’ll be installed tomorrow!

                My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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                • #9
                  Hey -- good luck with it! Post results.

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                  • #10
                    Originally posted by oldboat1 View Post
                    Hey -- good luck with it! Post results.
                    Will do! I’m just hoping the tach is ok...
                    My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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                    • #11
                      If the starter has suffered from repeated hammer " taps " then it may need a new starter.-----The magnets can not take that abuse.-----On Mercury motors this type of starter used to have a warning.-----Said---" do not stroke with a hard object "

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                      • #12
                        In responding to tachometer question I can say that I have never used a digital tack. However they all have a few things in common.
                        1. They must all have a 12 volt supply of power with ignition switch on.
                        2. They must have a good ground.
                        3. They must have a input wire connected. For most OMC engines this wire is usually a yellow wire with a gray stripe..

                        My first test would be to use a volt meter to test if ignition wire is showing 12.5 volts plus with switch turned on.. Also be sure tach is attached to a good ground wire.

                        Having said and assuming that all this checks out you might want to see that your rectifier is good on your engine. If it is not functioning properly your tach will not operate. Also in response to your question about aftermarket tachometers, they all should work well on your engine. There are setting on the back of almost all marine tach's that have to be adjusted to the pulses that of your charging system. Almost all of your V-4 and V-6 OMC outboard engines would be adjusted to 6.

                        I hope some of this information helps.

                        85Skeeterman

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                        • #13
                          85Skeeterman, thank you for that info!! That’s the type of stuff I need to effectively troubleshoot this tach (wire colors and whatnot).

                          I will be firing the OB for the first time tomorrow, I have new plug wires coming (ripped off a plug wire connector while checking compression). I will check the items you detailed above.

                          Thanks again!
                          My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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                          • #14
                            So I’m not able to fire the motor today. The new plug wires got delayed, so they are now due in on Tuesday.

                            One thing I have noticed is that the tilt/trim appears to have been added after the fact. It is working fine, but has the switch on the dash. I’d like to try and convert it to the switch on the throttle handle. Is there a switch I can buy that will screw to the non tilt/trim OEM handle?
                            My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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                            • #15
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                              I know the til/trim switch question is straying from the thread topic, but I thought it would be better to simply add it here instead of a whole new thread.

                              Anyway, here are a few pictures of the control. I took a close picture of the two hole at the top of the lever that look to be meant for the tilt/trim switch. Any info on a part number (or if it is even available) would be great! My internet searches keep showing newer switches that don't look like they'll fit.

                              My SS180 https://forums.iboats.com/forum/owne...180-by-bignuge

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