2002 Mercury 75hp 2 srtokes LOSS OF POWER

[frankfort]

Hi, I am new to boating, I have a 2005 tracker bass boat with a 2002 75hp 2 strokes Mercury, I replaced the spark plugs, and fuel filter, took it for a run, ran good for 20 to 30 min. at approx. 40mph than all of a sudden the speed dropped to 25mph while I still had full throttle. it starts no problem but no power. Can someone please HELP me.

 

[enginepower]

Need to run it on the muffs and pull one plug wire at a time and see if you have rpm change on all cylinders. You probably dropped spark on a cylinder due to faulty switch box or ignition coil or such.