Tacho test results, 1995 johnson 115

[skiers5]

Hi All after consulting the manual at 1000rpm the grey tach wire should show 9v +or- 1v. Came in at 2.38v, disconnected the grey wire from the terminal strip as pictured and it raised by 1v as it should. Disconnected the VRO Amphenol connector it also raised the reading by about 1v.

Ignition on, engine not running connected volt meter to engine harness grey lead, disconnected tacho from circuit 0.03v was the reading.
In the pics attached of my engine the box on top of the L/H cylinder bank what does this do my manual does not show this component. The pic of the terminal strip is it possible to have the yellow leads attached the wrong way around?

Does any body know if the setting on the back of the tacho would effect max rpm reading i also believe when the tack drops off so does the charge rate drop the rpm the charge rate returns to normal. 4 to 4500rpm the tacho drops out no charging. Keep tacho under 4500 no problems. What the hell is going on with this thing.

Any vice admirals have some ideas on this issue, all input is greatly appreciated
Thanks to all
Dean Cameron

[boobie]

What type of voltmeter are you using to check voltages ?? The manual says to use a peak reading voltmeter.

[skiers5]

What type of voltmeter are you using to check voltages ?? The manual says to use a peak reading voltmeter.

Reads actual dc voltage, should it not display 9v +/- 1v @ 1000rpm not 2.38v ?. Thanks for offering assistance.
Dean

[Faztbullet]

pics attached of my engine the box on top of the L/H cylinder bank what does this do

That is the ignition pack....

is it possible to have the yellow leads attached the wrong way around?

On the OEM rect/reg the striped yellows attach together......

4 to 4500rpm the tacho drops out no charging. Keep tacho under 4500 no problems. What the hell is going on with this thing

It could be the rect/reg is failing, stator problem or your loosing the 12v connection on purple wire as this turns rect/reg on

[Silvertip]

Yes -- those numbers on the back of the tach are for calibrating the tach to the number of "pulses" coming from the charging system. They do not relate to the number of cylinders the engine has. Your engine has a 12 pole alternator that produces 6 pulses per engine revolution. Therefore that dial needs to be set to 6P.

[boobie]

It could also be a bad tach. The tests on the gray lead should be run with a peak reading voltmeter or an ohmmeter with a DVA adapter. With those meters you should have 9 +/- 1 volt.

[skiers5]

I'll check the purple wire for 12v, yellow wires with grey strip are matched, thank you for the advice.
Dean

[papyson]

i think you have a rectifier failing in the charge circuit which also feeds the tach....known problem on that vintage and that engine..do you have a rectifier only charging system?the rectifier only will just be a rectifier attached to the engine block on the starboard side of the engine...the regulator if you have one will be attached to the top of the engine and will not have the rectifier on the engine block.....