I run an SR4.7 with a Merc F50Efi 4-stroke.
Max speed around 32-33kts
Fuel consumption at steady 28ish kts: 0.6l/nm
I used to have a Twatsoo 60hp 2-stroke on there, which was around 1.5 kts faster, but when cruising at 28kts, it delivered 1.0l/nm
If money were no object, I'd suggest a Yam F70 4-stroke, but they're £7295.
If you want to spend £2k-£2.5k, then I'd suggest a 2003 onwards Merc/Mariner/Yam 50/60hp 4-stroke (Efi)
If you want to spend £1500, then look out for a late 1990s Yam 60/70 2-stroke, but these are rare.
If you want to spend around £1000, then an older Yam 60/70 or a Soozook DT65 from early-mid 1990s would be my choice.