Small Engines (Lawn Mowers, etc.): 23 Vanguard firing one side only, horz, plug wires

Question
Hello Ben, I have a 23 Vanguard Horz. shaft 380400 model.I have it in a small mud boat. Coming in from fishing one cylinder quit firing.Motor has 49 hours on it and I have never turned more than 3420rpm.It sounds like the exhaust is coming straight out of the cylinder,it is that loud.No internal knocking or grinding.Being that I was out in the lake I Idled in for at least 1 mile running on one cylinder.I pulled the plug wires to figure what cylinder was not firing, went about 1/2mile and engine quit completly.Got home pulled plug on first cylinder out it has a good spark.The cylinder that got me almost in has no fire.Very confused
Thanks in advance for any help

Answer
John
You may have a fouled plug change both of them. when you get it running and while it is running pull a plug wire off see if it quits,if it does then that cylinder is not firing.You may have a bad coil. The Vanguard use two ignition coils, one for each cylinder.Spark plugs do go bad even when they are new