Funny you should mention that Nev, I asked my CFI about premix for my 582 a few weeks ago and he said that to store it premixed. Now, I remember Yamaha was very specific about stale fuel causing holed pistons in outboards, but these were not premix fuel motors. I have ordered a new crate premix 582 engine to put in my Thruster, not because the old one is cactus but to simply have reliable as possible.