1987 Mercury 45 hp Classic fifty poor performance

[tchaike9800]

I have recently purchased my first ever outboard motorboat. I have totally dismantled and successfully reassembled several 4 stroke car engines, never a 2 cycle engine. The Mercury will begrudgingly rev up to 5500 rpm out of the water, however only 2300 rpm in the water. I have 120 compression on all 4 cylinders. The top two plugs check good on a spark tester. The bottom two plugs get no fire either with the tester in line or without the tester in line. After running the engine for a few minutes and pulling all four plugs, the top two have blackened on the tip and the bottom two are as clean as when they were installed. The top two are also slightly damp with fuel and the bottom two seem to be entirely dry. I would like advise/help in troubleshooting back to the "no spark" issue on the bottom two plugs. Thank you so much, from a person who is new to 2 stroke.