99 3cyl 2 stroke 40 lost WOT rpm

[Joel Caillouet]

I'm running 99 40 3cyl 2 stroke on my 20/42 aluminum tunnel it used to run 38mph at 5500
now it only runs 31 @ 5100 any suggestions? Compression 120x3

 

[Joel Caillouet]

Idles and seems to run fine no bogging or anything

 

[guyjg]

May not be running on all 3 cylinders. See what the plugs look like...should be brown.