90s era Mercury 115/125 (2+4 ) for Seafari?

[McGillicuddy]

Thanks Tucker, Any thoughts on mpg, compared to other motors of similar hp.
I'm looking to replace a strong '83 i-6 to get more range by increasing my mpg.
We're losing our local fishing grounds

I'm primarily looking at older Merc 150 2.0L and these 2+4 115/125.

That merc 125 seems like a nice compromise by I'd like to get more insight on fuel econonomy, and how they run in the mid-range rpms - also heard it said they either idle/troll or go fast.