Just a little post from personal experiance
I had an old wilson flyer 17 that had been built very heavy as a self finish
I bought it without an engine when money was tight and fitted a twin cylinder 45HP, It ran ok but was not always a good starter and did not match the boat.
ASAP I swaped the engine for a new 60HP 2 stroke. Different boat after that, straight onto the plane good top speed etc etc
Fuel economy was much better with the bigger engine as there was no need to run at full throttle.
I used the same principle when fitting out Alfresco, recommended engine 230 HP , I fitted a 260
we cruise her 1000 RPM below max revs and get good fuel economy. If we want to fly about we can, but it sucks up the fuel.