Following the manual instruction on setting the timing on a 1994 3.0L mercruiser engine when I jump the two white leads on the distributor there does not seem to be a change in timing advance. My understanding is that when the leads are connected the timing is returned to base which should be 1'BTDC. When the jumper wire is removed the timing should advance to around 12'BTDC. Any suggestions on why jumping the wires does not impact the timing. Suggestions?