1994 Johnson88HP 2 stroke tachometer help

[Chris_94_Sprint_TX]

My tachometer is not working and I am not familiar with how tachs are wired to outboard motors. What my gauge is doing is not showing any reading when running but when I shut it down it registers 1,000 rpm. Any ideas on what to check first or have a wiring schematic/diagram?

Chris

 

[mjf55]

On the back of the tach there will be a purple wire ( 12 volts when the ignition is on, black which is ground, and a grey which is the sender to the tach.
With the ignition on but not running, measure purple to black ( 12 volts or higher ) and grey to black. Should be 0 volts.
Now with engine running at 2000 rpms, the voltage between grey and black should be between 3-7 volts AC
Give it a try, let us know what happens.

 

[mjf55]

Baleated

 

[emdsapmgr]

When you shut down the voltage to an electronic gauge, the needle can come to rest anywhere. It has no bearing on anything when shut off.

 

[Chris_94_Sprint_TX]

On the back of the tach there will be a purple wire ( 12 volts when the ignition is on, black which is ground, and a grey which is the sender to the tach.
With the ignition on but not running, measure purple to black ( 12 volts or higher ) and grey to black. Should be 0 volts.
Now with engine running at 2000 rpms, the voltage between grey and black should be between 3-7 volts AC
Give it a try, let us know what happens.

I'll give it a go tomorrow. Have a couple of other goodies to install too (Humminbird 686 and a 3 bank charger). I'll look under the console while I'm there.

Thanks
Chris

 

[emdsapmgr]

The tach is driven from a signal that the engine produces when charging the battery. Usually, when the battery quits charging, the tach starts to act up. Your 88 special was marketed as an "inexpensive" alternative to the 90 hp version. As such, it does not have a regulator in the charging system like the 90. Rectifier only. (that may be good, as the rectifier is much cheaper. Likely replace the rectifier and your tach issues will be solved.

 

[Chris_94_Sprint_TX]

The tach is driven from a signal that the engine produces when charging the battery. Usually, when the battery quits charging, the tach starts to act up. Your 88 special was marketed as an "inexpensive" alternative to the 90 hp version. As such, it does not have a regulator in the charging system like the 90. Rectifier only. (that may be good, as the rectifier is much cheaper. Likely replace the rectifier and your tach issues will be solved.

IT may have been replaced already. PO told me most of the motor had been rebuilt ($850 worth of parts)

Chris