I've read that you need to ground the purple/white wire to set the timing on merc engines.
Is this only the case on the efi engines? I have a carbed HP500 with TB IV ignition.

CTA

PS-need v8-22 module,anybody?

You should groung the wire before starting engine to set timing or adjust carb then shut down before detaching.

On a TB IV, you don't have to gound anything, just on TB V's.