Erratic tachometer 89 60 horse Evinrude

[bcj.jones]

1989 Evinrude 60 hp. Just installed it and replaced the old 50 hp evinrude. The tachometer is brand new and was working with the old 50 hp. Once I hooked up the 60 the tach will work at idle just fine, and also seems to work on partial throttle, but on full throttle is where it seems to mess up the most. It will sometimes bottom out and sometimes it'll go all the way around back to 0 when full throttle is applied.

I'm obviously leaning toward the motor, but not sure where to start checking?

Thanks for your help!

 

[jbuote]

Not a pro, but I think that's probably the regulator or rectifier on the engine..
Is it charging your battery when you run it?

The pro's here will give better info I'm sure, but I'd probably start with troubleshooting the regulator/rectifier or at least testing them to see if they're good anyway...

Edit: Another thing too.. Make sure all connections are clean and tight.. (Battery terminals, connectors etc...)
Probably a good thing to double check before going too far...

 

[jimmbo]

Check for loose or corroded connections at Rectifier, and the main cable connector. Wiggle the connector while watching the tach. Also wiggle the wires coming from stator to the rectifier.

 

[F_R]

Does your motor have a voltage regulator or does it have a rectifier only? If it has a regulator, the tach must be connected to the correct wire, otherwise the regulator cutting in and out will mess up what the tach is looking at as its input signal.

Without hunting up the diagram for your motor, the tach signal wire normally is grey and connected to the yellow wire with grey stripe at the alternator.

 

[F_R]

Did you reset the switch on the back of the tach to 6 pulses (12 pole) when you went to the 3 cylinder motor? Again without knowing what the 50 was, I'm supposing it was 5 pulses (10 pole)