Hello, I'm about to adjust the timing on a 1988 merc. 454 330hp. Got the light, marked the TDC line on the balancer and the engine says 8° BTDC . No problem except, the mercruiser manual says its important to jump the purple / white wire to ground coming either from my distributor or the control module attached the the exhaust manifold ( old manual, it's not clear which) . I cant find a purple and white wire . There are only 2 wires attached to the distributor wht/red and wht/green there is no vacuum advance . If you know which wire I need to ground, I'd appreciate it. Thanks

Being a 1988 its a TB4 not a TB5 which is what your reading about. The TB4 does not use base timing mode, so just hook up the light, point n shoot

If that's the case I'm at 0° instead of 8° I thought if it was off by that much it would run like crap. It's not smooth or perfect, but not awful running.

I have an '88 TB IV ignition, no shorting of wires to check timing. Cut from the Merc manual on how to set timing;

Too slow to post LOL, AllDodge had it covered

At 8 deg slow it would still run smooth, just be low on power, maybe hesitate on take off.

It’s a very mild engine, that’s why.

Something with more camshaft and non heated intake would refuse 0 degrees.