0.8/0.9
0.8 to 0.9mm
.031 is the correct gap for this vehicle
The correct spark plug for the 1991 model, 200 hp Mercury outboard, is a NGK brand, BU8H.
0.035"
.032-.034
.030
The 1991 Mercury Marquis spark plug gap is .034. Most spark plugs will be pre-gapped by the spark plug manufacturer.
.8 to .9 mm
That's not really what's going on. The coil makes the spark, the distributor distributes the spark to the correct plug. If the distributor is not in the correct position, the spark does not go to the correct plug, or goes to the correct plug at the wrong time.
The standard plug for a 99 Vulcan classic is the NGK DPR5EA-9. The 9 stands for the preset 0.36 gap.
The correct spark plug gap is .044
correct part for js45a spark plug and filter