Yanmar 1GM10 Tachometer retrofit-help required please?

mickywillis

mickywillis

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RESLOVED!!! Yanmar 1GM10 Tachometer retrofit-help required please?

NOW RESOLVED!! See my last post. Thanks for the help, but the problem was fairly simple!



Have recently purchased a Type B control panel to fit to my 1GM10, which will finally give me a tachometer/recv counter (with any luck!)
On the front of the tacho is P=97 which I assume to be the number of teeth on the flywheel, can anyone confirm that this is the correct number of teeth on a 1GM10 flywheel ( or have a look at the tacho fitted to your boat if you have a 1GM10 and type B panel)
I have also purchased the item below:
http://www.ebay.co.uk/itm/180941753...X:IT&_trksid=p3984.m1439.l2649#ht_3047wt_1091

This has been fitted into an adapter to fit the bellhousing where the correct Yanmar sensor would fit. I have correctly measured the air gap between the base of the sensor and the flywheel teeth to the gap given on the data sheet of the sensor.

Luckily I have an old 1GM10 at home in the garage which was purchased as a fixer upper due to head damage, so the head is off and the strter motor in place. In effect I can turn the engine over on the starter motor and get it spinning to a reasonable speed. Trying this to test the setup before I fit to my working engine.

Problem I have is the tacho just isn't reading. When I turn the ignition switch on, the needle on the tacho jumps up very slightly ( I believe this indicates the tacho is sensing correctly as it does not jump up when the battery is disconnected?) Engine spins over fine on the starter (not sure how many RPM's though) and teh B type panel seems to function correctly (warning lights, illumination and warning buzzer all work)

Question is this. Would the tacho show a reading when turning the motor over on the starter or is the RPM on cranking not quick enough?
Also, the sensor has 2 wires, a red and a green. Should one of these wires be connected to ground or is it sufficient to connect to the 2 wires as shown on the Yanmar wiring diagram to the 2 leads on the wiring harness. Is there any way of testing the output of the sensor without an oscilloscope to view the minimal voltage output or without causing damage to the sensor? I also assume that the Yanmar tacho has some sort of voltage amplifier to step up the output of the sensor to a level to convert to drive the tacho needle assembly.

Thanks in advance if you can assist.
 
Last edited:
I once made a tacho. for my 2GM20, using a similar pick-up to your ebay part, but obtained from Radiospares. It drove a milli-ammeter through a frequency to voltage chip.
The 1GM10 has 97 teeth, I'm fairly sure. The 2GM20 has 114.
I found that the gap between ring-gear and pick-up needed to be rather less than that specified in the Yanmar manual, probably dependent on pick-up sensitivity and the circuit characteristics, that may be one issue for you. Also, cranking speed is probably a bit on the low side, and the battery voltage during cranking might be a bit low for the circuit.
I got my system working by setting up with a gear-wheel mounted in a lathe, so I knew the speeds, gaps etc.
Hope that helps.
 
nigelmercier said:
The sensor must have 3 wires, from the picture the third is the braided shield. Connect as per the sensor instructions, with the output wire going to the tachometer.
Click to expand...

The wiring diagram for the engine shows two wires with the sensor body being earthed...... presumably via the engine block.
 
I wonder whether the sensor is compatible with the Yanmar tachometer? The Yanmar workshop manual says the sensor resistance should be 1500-1700 ohms, so it would be worth checking the resistance of your sensor first.
 
Problem was fairly simple to resolve.
I checked the output of the sensor with a digital meter on AC scale and was obtaining 0.9 Volts at cranking speed.
So I knew the sensor was working within tolerances and the output voltage was well within spec.
I then connected the sensor directly to the multiplug behind the tacho, keeping the original multiplug connected to provide voltage up to the tachometer. Using pins directly into the multiplug, I connected the sensor into the multiplug and cranked the motor. It worked! The tacho read 500 RPM at cranking speed (about right considering the head is off the old engine)
So I can only assume (and indeed have now confirmed with meter) that the orange and red/blue wires within the wiring harness are open circuit.
So all I need do now is fit the sensor on the boat engine and fit the B type control panel somewhere where I can see and enjoy the new rev counter!
Happy days!!
 
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