From My understanding if you go with the Verado's or any other four stroke from what you have you will have to re-wire everything from throttles to gauges which = $$$, My brother has the 225's Mec Offshore old two strokes and we burn 60 gallons a night running around 5500 RPM's, when we take it easy only around 40 gallons with twins. He was going to switch over to Opti’s but the dealer said that the way he drives the fuel burn would be about the same and if he was worried about fuel consumption to take it easy on the throttles while running.
Another boat I fish on has a Verado 275 on a 23' Seacraft and we burn 15 gallons a night new boat and so far no problems with the engine.
The boats I fish on that have Evinrudes fuel injected engines burn a little less fuel just depends on how you drive the boat.
If you are making a long run to the grounds might be cheaper to get a bigger tank put in for the short term cheaper fix or take it easy and run around 3500 RPM’s