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tach not working on 1989 70 hp

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  • tach not working on 1989 70 hp

    along with the tach, the temp guage-sender combo isn't operating right either. New sender...foreign $10 of fleabay...took a chance.. 33-240 ohms.....seems right...had an older red OMC temp guage. thought I wired them right...sender connection, ground connection, light connection ignition connection.... soon as you turn the ignition on... the gauge shoots to the top (240 degrees).

    as for the tach... I bought a three wire harness that comes off the side control to power up the ignition and tach signal... the ignition part works.... so I know the harness is making contact.... the tach was a tempo I had .....its older for sure.... Im going to try and try a different tach soon...but how do I test the gray wire or the wiring on the motor to know if I am sending a signal... and possibly know I am charging....

    hope to hear from someone...

    how would I go about trying to figure if a temp guage is compatible with a sender?...... I had a mismatched problem on my last boat build... but the temp reading was only off by about 20 degrees or so.......


    bob

  • #2
    Having a gauge peg as soon as the key is turned to ON indicates that the sensor terminal of the gauge is grounded.

    The gray wire?..... Check the rectifier as 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

    ********************
    (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.
    Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

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    • #3
      im going down to do the rectifier test....since I have a spare, and since that rectifier on the engine was getting super hot when the motor was running...

      Comment


      • #4
        Originally posted by Joe Reeves View Post
        Having a gauge peg as soon as the key is turned to ON indicates that the sensor terminal of the gauge is grounded.

        The gray wire?..... Check the rectifier as 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

        ********************
        (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.
        hey Joe ( sounds like a Jimmy Hendrix song!).....I had a used rectifier and checked it out...seemed good by your test method...I checked the rectifier before the tach, because it was getting hot....so I started there....pulled the wires on the motors suspect rectifier and it failed the test!!! re;placed the rectifier and the tach now works! yeah....great advise..... thanks...... going to look at the temp sender tomorrow...have to cut grass now....bob

        Comment


        • #5
          The grass.... UGH!... I cut the grass. The grass lays dormant for about three days... then grows eight inches overnight!
          Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

          Comment


          • #6


            this is the reading on my suspect , bad sender.....for reference I have four other BRP brand senders that I checked and they all read about 10 on the same scale.... this looks like it reading high 30's...but I have never "adjusted the scale on the meter... the regular senders are supposed to read 33- 240 ohms... but in any case it is reading different that the four good ones I have.....im going to hold off pulling the gauge in the dash until I hear from someone here.....bob

            Comment


            • #7
              Did you zero the meter first by shorting it's leads together & adjusting to zero with the Ohms Adjust knob?

              Note: Temperature sender value at 72 Degrees F should be around 800 Ohms.

              Note: In your picture the meter is set on Ohms (R)x10 so the reading you are seeing is around 3.8 Ohms.
              Set the meter to Ohms (R)x1 to get an idea where you're at.

              Note: Zero the meter every time you change scales & use a scale that preferably gives you a meaningful reading towards the middle of the dial.

              Comment


              • #8
                Yeah, the gauge looks like it's reading about 38 ohms, but as "Fed" asks... I was wondering if the gauge was zeroed to begin with. I sort of suspect it was... but you do state "I have never "adjusted the scale on the meter."... Simple matter, connect the meter leads together, adjust the setscrew below the needle.

                Edit due to "JBuote" reply below. I overlooked that scale dial (X 10)... 38 ohms = 380 ohms.
                Last edited by Joe Reeves; October 8th, 2017, 04:57 PM.
                Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

                Comment


                • #9
                  I know I'm rusty with meters, and mine is auto-ranging so haven't used analog in a while, but...
                  ​Isn't the range dial set at "Rx10", so a reading of 38 would be 38 x 10 = 380 Ohms??

                  ​I could be wrong, and truly don't mean to confuse any issue here..
                  ​It's just that's the way I remember it anyway...

                  My apologies if wrong...
                  ​(and yes.. as Fed and Joe said.. Should zero the meter first.. )

                  Comment


                  • #10
                    Originally posted by jbuote View Post
                    I know I'm rusty with meters, and mine is auto-ranging so haven't used analog in a while, but...
                    ​Isn't the range dial set at "Rx10", so a reading of 38 would be 38 x 10 = 380 Ohms??

                    ​I could be wrong, and truly don't mean to confuse any issue here..
                    ​It's just that's the way I remember it anyway...

                    My apologies if wrong...
                    ​(and yes.. as Fed and Joe said.. Should zero the meter first.. )
                    Good Catch JBuote
                    Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

                    Comment


                    • #11
                      Yeah 380 Ohms jbuote.
                      I left my post unaltered so your post would make sense.
                      I have no idea what I was thinking when I said 3.8 Ohms.

                      Comment


                      • #12
                        well.....I replaced the temp gauge......and it looks like the set up is working....first off the guage doesn't peg instantly when the ignition is turned on...secondly when I left the water off the lower unit in about 30 seconds the guage started to climb off the lowest reading of 120 degree.....it seems when I run the motor with the muffs the temp would not come off 120 degree...but the heads were ice cold even after running 15 minutes.....so while I do have a thermostat issue,.... the gauge and sneder seem to be working........

                        the tach fix created another problem...gee cant get away from them......I have an alarm going off now....constant every
                        1 or 2 seconds...wont go off while motor is running... if I rev the motor the alarm picks up its cadence...... so thinking it is certainly tied to the tach signal....


                        will post water thermostat question in another post!

                        bob

                        Comment


                        • #13
                          My V4 does the same Bob, I believe the combined pressure of the muffs & the water pump lifts the poppit valves and the water never gets hot enough to open the thermostats.
                          My plan was to drill a hole in the dead side of the muffs and run an open pipe up to about the bottom of the lower cover so the motor only allowed pressure from the water pump without the muffs adding to it. Never got around to it, maybe one day.

                          Machine gun beeping that goes up & down with rpm is the NO oil alarm on the VRO.

                          Comment


                          • #14
                            Originally posted by Fed View Post
                            My V4 does the same Bob, I believe the combined pressure of the muffs & the water pump lifts the poppit valves and the water never gets hot enough to open the thermostats.
                            My plan was to drill a hole in the dead side of the muffs and run an open pipe up to about the bottom of the lower cover so the motor only allowed pressure from the water pump without the muffs adding to it. Never got around to it, maybe one day.

                            Machine gun beeping that goes up & down with rpm is the NO oil alarm on the VRO.
                            how do I disable that no oil alarm??
                            bob

                            Comment


                            • #15
                              Sign up today
                              Originally posted by bob johnson View Post
                              how do I disable that no oil alarm?? bob
                              I see no mention of using pre-mix in this topic, and unless I've overlooked it.................................

                              You DO NOT want to do that unless you intentionally desire to blow that engine up! A beep every other second indicates that the VRO has no oil being pumped to it... OR... the VRO has failed.

                              Possibly it's just a matter of air in the oil line. As the horn is beeping every other second, apply pressure to the oil primer bulb. Did the beeping stop? If so, did the beeping start again after a short time? Again, if so, prime the VRO as follows:
                              ********************
                              (Priming The VRO Pump)
                              (J. Reeves)

                              When hooking up or installing a VRO whether it is a new or original VRO pump, it must be primed in order to dispel any air that might be in the oil line.

                              Have the Oil line attached to the engine fitting BUT detached from the VRO. Add a piece of fuel hose if necessary to the oil line so that it can be aimed into some sort of container.

                              Pump the oil primer bulb, catching the oil flowing out of the line into the container until you are absolutely sure that you have rid the oil line of every bit of air that might have been trapped there.

                              Now, connect the oil line to the VRO and secure it. When the oil line is secured, apply pressure to the oil primer bulb ONE TIME only. That's it.
                              ********************
                              Should the beeping continue after the above procedure, replace the VRO or switch to pre-mix as follows:
                              ********************
                              (VRO Pump Conversion To Straight Fuel Pump)
                              (J. Reeves)

                              You can convert the VRO pump into a straight fuel pump, eliminating the oil tank and VRO pump warning system, but retain the overheat warning setup (and fuel restriction warning if so equipped) by doing the following:

                              1 - Cut and plug the oil line at the engine so that the oil side of the VRO pump will not draw air into its system. Trace the wires from the back of the VRO to its rubber plug (electrical plug) and disconnect it.

                              2 - Trace the two wires from the oil tank to the engine, disconnect those two wires, then remove them and the oil tank.

                              3 - Mix the 50/1 oil in the proper amount with whatever quantity fuel you have. Disconnect the fuel line at the engine. Pump the fuel primer bulb until fuel exits that hose with the tint of whatever oil you used. Reconnect the fuel hose.

                              That's it. If you want to test the heat warning system to ease your mind, have the key in the on position, then ground out the tan heat sensor wire that you'll find protruding from the cylinder head. The warning horn should sound off.
                              Our Questions Require Answers... If You Refuse To Answer Our Questions... How Can We Answer Yours?

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