tachometer for 225 johnson not working

[snichols]

Trying to figure out what to do. I just got my boat back from the shop and the new tachometer they installed doesn't register at all when motor fires up. Tach lights up and sets to zero but never rises. All wiring at the console seems right. Any suggestions?

 

[Chris1956]

See if the tachometer signal wire (grey) has continuity from the tach to the voltage Regulator (or rectifier, whichever you have). Sometimes they ground out, or the voltage regulator/ rectifier go bad.

What year and model number is your motor?

 

[snichols]

Boat is a 1990 wellcraft 20 sport fish the motor is a 1990 i believe 225 johnson. Motor was bought second hand and just switched to this boat. I bought a hand held tachometer and wrapped the wire around the grey wire buy the console and got no reading. Only place i was able to get any reading was on the actual spark plug wire. When i get home i will look for the motor model number

 

[snichols]

Ok so I rechecked the wires and found out that the shop wired the Tach into the wrong wire. I found the grey wire and it hooked it to the sender on the tach but now when i turn the key on it zeros out and when the motor first fires the needle will jump like its going to read which it never did before but then drops straight back to zero when motor is actually running

 

[Chris1956]

Normally a tachometer will have +12VDC (purple), ground (Black) and tach signal (grey). Do you have the correct readings on the three wires? If so, check the grey wire connection at the voltage regulator.

 

[snichols]

Ok so i feel like im back at square one. I checked the volts at the tachometer and purple shows 12v ground shows good. Heres where I become confused. When the grey wire is unhooked from the tachometer sending terminal it reads 16v. As soon as i touch the grey wire to the terminal and re check the volts it reads as a dead wire 0 v. But will read 16v again as soon as it is removed from tachometer.. I dont know how a hot wire can do that. Also after motor ran for about 10 mins the grey wire started showing only 8 v .

 

[snichols]

No Title

 

[Chris1956]

The tach signal wire from the VR should show some AC voltage. If the tach grounds it, and you do not get a reading, maybe the tach is bad? Is the tach set to the correct setting for your motor?

 

[snichols]

Ya tach is set correctly. Tachometer may be bad just odd being brand new.

 

[gm280]

snichols, before sending the tach back or trashing it, try one more thing. Remove the gray wire from the tach and use your Tiny Tach connected around that gray wire. Does the TIny tach work? If so, your in dash tach is bad, but if, like I think, the rectifier/regulator is bad...