I'm going to agree with the idea that Encourage merely disables the chance to burn/paralyze/flinch/freeze, but still keep the effects that always occur. (Recoil, stat drop...etc)
On how much it'll boosts moves by...I'm going to guess 10%, but anything between 10% to 20% is viable. Life Orb gives a universal 30% boost, but comes at a 10% HP loss per attack move and cost an item slot, whereas the type-specific items grants 20% to that type. (Muscle Band and Wise Glasses are 10%) This ability is automatic (ie. no item cost), and the tradeoff is quite minimal, so unless GF severely gimps the baboon's stat in favor of an overpowered ability, it's not going to be something ridiculous like 50%.
On TurboBlaze and TeraVoltage, anyone else get the vibe that it's going to be the Uber's form of adaptability? 2x STAB for Fire and Electric moves, respectively, sounds pretty good.