This was on my boat in 02 when I bought her and I think it was supplied standard with the outboard powered versions. It has a slot cut out to enable the outboard to lift well clear of the water. This was fine until I changed the engine from a 15HP 4 stroke to a 30 Hp 2 stroke when the larger engine was too bulky for the cover. It may be that for a Yamaha 9.9HP it does not need a slot for the leg to lift at all and it it would be a simple GRP project to glass it over. The corner of one side of the slot needs repair but the cover would clean up and be a real benefit to someone without a cover and far easier than making one from scratch. The cover keeps most of the weather and following seas away from the outboard although of course it is open at the bottom. It also make the rear of the boat much more presentable, covering over the engine hole.
It would be a shame to bin it as someone , somewhere would find it useful so let me know if you want it, you will need to pay postage but quite light so should be under a tenner.