Ok fellas...318 help needed , Mpg , reliability and enough power ***for a big boat !!!

My 72 Newport stock 400 except for 383 four barrel intake and edelbrock 600 is a nice cruiser gets decent milage for its size and has decent get up and go.
72 400 190 hp / 310 tq
72 318 150 hp / 250 tq

It should be pretty easy to get up to the power that i have.

If it was me i would just throw a moderate cam and four barrel on it and call it a day. If you dont like it, you could always change engines later down the road.