i need help beating the 7th gym in emerald?

[Will O'donnell]

i have a:
Breloom Lvl.42
Kecleon Lvl.30
Blaziken Lvl.39
Sandslash Lvl.25
Magnemite Lvl.28
Tentacruel Lvl.33.... i cant beat the 7th gym!!!! please help me!!!