[captaingene]

I have a converted 1986 Wellcraft V 20 with a 2013 Mercury 150hp 4 stroke . I am using a Mirage Plus 17 Stainless
3500= 21kn
4000 = 25 kn
5000 = 32kn

I think your engine should top out at 5000. I would check height of engine first. I had to raise my engine one hole.

I would highly suggest adding trim tabs greatly improved handling of my V 20 hull used Bennett sport tabs ....