I've heard of a few guys on here calling up Grady White and getting a specific maximum weight limit, which almost seems to be the bigger issue as opposed to the maximum horsepower rating. Back in 1996 sure, the maximum horsepower rating was 280 hp, but there weren't the heavier/higher horsepower 4 stroke motors around back then like there are now. Which makes for a pretty big difference in terms of weight. Per Google, your current motor appears to weigh around 500 lbs, of which 250 hp is going to be your max as I don't believe anyone makes a 275 hp anymore and I think 300 hp would be a bit overkill. Mercury is likely going to be your lightest option, of which their 225 hp FourStroke series outboard only weighs 475 lbs and their 250 hp FourStroke series weighs 527 lbs. So, essentially either 25 lbs less or 25 lbs more than your current outboard, depending on the horsepower level you want to go with. If you like your current setup and how the boat sits and performs with that horsepower/weight, I think either of those options would be fine for you as adding 25 lbs in the stern isn't likely something you'll notice at all. The only potential issue I can think of would be losing 25 lbs in the stern with the lighter motor and potentially having the boat be a bit more bow heavy. Though, I don't imagine that's likely to happen. Also, on my boat I've got a 2004 Yamaha F225 four stroke and it has a dry weight of supposedly 583 lbs per Google. Some consider her to be underpowered, though I don't see that as an issue considering she still tops out at around 45 mph and gets up on a plane just fine. So, I don't think adding a little more weight to your boat, which you and I have the same hull, would be an issue.
Comparatively the Yamaha F225/F250 are going to weigh around 551 lbs, depending on the model but will likely cost quite a bit more than the Mercury and you only get a standard 3 year warranty with Yamaha as opposed to 5 with Mercury/Suzuki. The Honda BF225/250 will be 622 lbs and the Suzuki DF225-DF250AP are going to be around 606-639 lbs. As mentioned above, Yamaha typically only comes with a 3 year warranty whereas the rest come with a standard 5 year warranty. Not saying you can't spend more and get an extended warranty with Yamaha, but that's also going to add to your expenses. If weight is going to be a potential concern, I'd go with Mercury, if not then I'd also consider Suzuki. If it were me, I'd look at the Suzuki DF250AP as it'll likely be one of your cheapest options, comes with a standard 5 year warranty, has fly by wire or digital throttle controls as opposed to mechanical, etc. If/when I need to repower, that will likely be my first option. The other "issue" with Mercury is that any of their 250 hp outboards are going to be a v8 as opposed to a v6, if that makes any difference to you. Their 225 hp FourStroke series is still a v6 though. Long story short, you've got several different options, though I think some of your biggest considerations would be which dealerships are local that are reputable and nearby, what kind of inventory is available and where, pricing and so forth. I think Yamaha would be my last consideration because of their pricing, as a brand new F250 with a 25" shaft and digital controls has an MSRP of over $30k before installation. If you shop around, I'm thinking you'll likely be able to find the Mercury/Suzuki for around $20k, or maybe even less.
