350 mercruiser fuel economy

[Dr. Hook]

My recently acquired v20 has the 350, 1992 model pre vortec with 2 barrel carb, rated for 210 hp I believe.
Alpha 1 outdrive
Just wondering what fuel economy I can expect.
Any recommendations on props would help too. What gain would I get going to a stainless prop?
If I ever repower I think that 4.3 MPI seems attractive. Same horsepower I have now but lighter and fuel injected.