Have a look at the red arror. this is NOT a yam but its in a similar position...its on the offside of the engine mount on the outside of the hull , there is a hole. have a look inside, so standing at the back looking forward. look on the right side of the mount, the part that is against the hull...you will need a large left handed screwdriver
. im sure its clockwise to undo. anyway try it, once undone 4-5 turns, then lift the engine up.the more you undo it the easier it is, this will expose the oil filler screw once up. you could try lift it up manually and down again a few times as maybe a air lock. then tighten the screw (not overtighten) and press trim and tilt button see if it works