It depends on the model and country. Here is a resource: www dot outboardshop com slash spark_plugs_twostroke dot html
Any motor should get spark with or without gas in it. The ignition system works off electronics and does not require fuel for it to work. Yes you should get spark.
What is the spark plug gap for a 9.9hp mercury outboard motor
The spark plug gap for a 2003 Mercury 125hp outboard motor is .040"
spark plug gap for a 1996 mercury 30 hp outboard motor?
3 spark plugs
.035"
.040
NGK BPR6HS-10 spark plug. Gap is .040
.40
0.25mm
NGK bpr7hs-10
.040