Mercruiser 898 replaced distributor ignition sensor now I have a miss

[BlueFin17]

I had a no spark situation and replaced the ignition sensor in the distributor with a Sierra unit. The motor fires right up and will idle but misses badly when I open the throttle. I have double checked the plug wires, replaced the cap and rotor along with the plugs. I noticed the tach acted funny when I throttle up so I disconnected it to eliminate it. I checked the ignition timing and found it to be about 4 degrees too far advanced so I set it back to 8 degrees. I then throttled up the motor and tried to check the timing to see if it was advancing but the light goes out at anything above idle. The light works on another vehicle so I know it's good. Question ,is the Thunderbolt box bad or the new sensor?

 

[NHGuy]

Recheck the wiring then, for that sensor. What about the ground on your distributor? Is the rotor seated? Cap, and wires on tight?

 

[BlueFin17]

The new sensor has a seperate ground wire which I connected to the block. Dist ground wire goes the the bolt holding the thunderbolt box the the manifold. That seems odd to me but it's been that way forever. Rotor is new and fully seated, I guess I am going to swap the sensor and see what happen's.

 

[BlueFin17]

I have found that the new Sierra sensor wires are opposite of the original sensor. Looking down at the distributor which rotates clockwise the original sensor had the green/white on the left and the red/white on the right and these were bolt on. The new sensor which is molded has the red/white on the left and the green/white on the right. I think this is messing up the thunderbolt advance and causing my problem. I will repost after I swap the sensor.