A few things that have been mentioned above would be that the maximum horsepower rating for the OP's boat is 250 hp, though if a 250 hp and 300 hp outboard are the same weight then I guess it would work? Idk, I honestly don't think there is much of a need to go over the maximum horsepower rating as Grady White's aren't really a speed boat, and I'm not sure if that could make for a problem with insuring the boat? I again personally wouldn't go with anything above the 250 hp rating, but that's just me, you can do whatever you want with your own boat, though it's just going to increase the price. I think the two biggest things that a 250 hp outboard will give you is slightly better mid range fuel economy numbers as well as resale value. When I was looking for a boat, I was trying to find one that had an F250 on it, but pretty much all, or at least the overwhelming majority, of the early to mid 2000's GW 228 Seafarer's had F225's on them. If you were to ever resell the boat, I think you'd probably have more interest from potential buyers with a 250 on it as opposed to a 225. To me,
I personally don't need to go over 40 mph, shoot I rarely ever go over 25 mph because whenever you do it just increases the GPH of fuel you burn. Some people care about having the maximum horsepower possible as well as top speed and those mid range fuel economy numbers, and again you'd probably get more interest in the boat as well as a higher selling price if you did resell it. I'm honestly kind of shocked that the Mercury is the same price or close to it, as compared to the Suzuki. I figured the Suzuki would be considerably less than both the Mercury and the Yamaha. As Ky Grady mentioned, I'd definitely call around and see who has what in stock and for what price. At the end of the day it depends on what you want to do with the boat and what your intentions are for the boat, whether you want to keep it for the long run, potentially sell it, etc. If you do plan on keeping it for the foreseeable future and don't mind waiting, I don't see any issue with spending a little bit more on the exact motor that you want to get. I just have the mechanical throttle linkage on my F225 and don't have any issues with it, though I would definitely consider upgrading to the fly by wire or digital controls. Say it is $5k more, if you kept the boat for the next 10-20 years then that additional $5k would likely be worth it in the long run. I again think it'll be mostly about what's available, when and for how much. Good luck and let us know what you decide on