Welcome to my world.
Also, totally agree with Psneeld.
So, for a 42 foot boat, you probably need about 65 hp to go 6 to 7 knots, a little more hp for high winds.
Having said that, I love my Sp 135
I get 1.5 gal/hr at 7 knots and if I cut back to 1500 rpm and aobut 6 kntos, will consume 1.1 gal/hr
It purrs like a kitten and puts me to bed every time