I’m currently running a Superboat 24CC. I really like the boat, but my wife is wanting something a bit bigger with more seating and a better ride in the rough water we frequently experience here.
Superboat’s Black Label 29 is one contender, but scouring previous posts I came across the Concept 30 Open. Good looking boat and seems to get positive reviews.
One appeal of the Black Label it is powered with a single 400r. I’ve seen a few Concept 30’s running twin 225 or 250 Optimax 2 strokes. I’m running a 300 Opti on the 24 now.
Is there a reason why a Concept 30 could not or should not be repowered with a single 400r or 450r? I’m not interested in ultimate top end, if it’ll run 60+ and cruise 40-45 I’d be happy as would my wife.

Thanks! I went by my local Mercury dealer this morning to discuss the possibility of doing the swap. He’d have to see the boat to give a price, but it’s certainly doable. Motor availability would be the biggest issue. 450r’s are somewhat available, but the new V10 400r isn’t readily available yet. He has yet to see one.
I did run the numbers are to running costs (silly I know). With having to buy 91 octane for the current optimax plus $50/gallon oil higher consumption of the bigger 4 stroke will be balanced out with 80 cent per gallon cheaper fuel. I don’t go to fuel docks as I’ve got 11 gallon fuel jugs and a pump.
Some consolation after laying out a chunk for a bigger toy!

Your going to want two engines because when it's loaded up it will be a dog out of the hole and may not want to stay on plane as easily at slower speeds. Loss of control around the docks. Converting from twins to single will kill the resale value. A single engine may work cruising with the wife, but will quickly lose it's appeal when you have a boat full of people. Maybe I'm just sour on all the terrible mistake threads where people thought they could save money on a big single engine boat only to want more power and only to end up with constant drive and engine problems. Doubt there will be less maintenance switching from twin stock any motor to a single racing outboard.

I owned a 30 cabin boat with 300 Verados. Mine was a 2017 and one of the last boats made with the bracket. Keep in mind that it is really a 28' boat. I would think it would run pretty decent with a 450r. It might of been easier to convert on the boats with brackets than the newer models. Mine topped out in the low 70's. It ran great up to 60 then it would get pretty squirrelly. It was a nice boat, but I know the prices went WAY up since I bought mine. I couldn't justify the current prices. I would say it was a mediocre boat as far as build quality. Lots of rattles, drove me nuts.

Coincidentally, I owned a 24 Superboat I/O too. I think the Superboat would of outran the Concept in any water. My Super ran 78 MPH with 425HP.

Might consider an Ocean Hawk. Affordable, more sport and less CC, but still a CC and she's a runner with just twins. Nice big cabin too, have seen them with generator in the console running AC in the cabin. Narrow deep V will eat up the rough stuff. I always considered it to be the perfect boat.