496 mag ho rpm
 

Seems like I am down about 300-400rpm. Going to change plugs this weekend to the NGK Laser Iridum Premium (Part no: ITR4A15/5599). My buddy was having a similar rpm problem just this weekend and changed plugs in both motors and he's back in business! (prop is fine-hydromotive 23 4 blade recreational cut, which had me at 5k rpm last year).