A 15 Lb Butterball takes about 2 Hours 15 Minutes with Portisserie
Maintain about 75% briquette load.
A top half foil shield helps with crispy skin and time.
If you are cooking on a cold day add a second sheet to complete the enclosure.
I let my nephew spit and balance the bird which explains the massive stack of hex nuts. He got a kick out of it so I let it be. Be advised that you will never spit something as far out of balance as that turkey is.