Why repower if the current motor only has 700 hours on her? I'd think a properly maintained HPDI motor would last at least 2k hours without much of an issue at all. Per the brochure located on the Grady White website, attached below, your hull is rated up to 250 hp. I've got a 2004 Grady White 228 Seafarer with a 2004 Yamaha F225 on her, and I honestly wouldn't go with anything less than a 225. My top speed with a relatively light load is right around 43 mph or so @ WOT. Cruising is at around 23 mph @ 3,800 rpm and burning around 8 gph of fuel, which I'm completely fine with. Anything less I imagine would get worse fuel economy, though a single 250 I think would be much more ideal for the hull. The boat itself, especially if you load it down considerably with fishing gear, coolers, food, water, full fuel tanks and so forth can get relatively heavy. Of which I again wouldn't go anything less than a 225, and think that the ideal hp for the boat would be 250. Seems like your hull weight is slightly different from mine, yours per the brochure says 3,350 lbs and mine says 3,510 lbs. Not sure if they changed it up in the early 2000's to add buoyancy for the extra weight of four stroke motors, but that's what the brochure says at least. In regard to repowering the boat, I'd also consider going with Suzuki and/or Mercury. Both of which I imagine are going to be considerably less money than the Yamaha, as well as Mercury is going to be lighter and they're also offering a 7 year warranty right now on all of their outboards.
Weights for the outboards would be around 475 lbs for your current HPDI, 525 lbs for the Yamaha F200 and 551 lbs for both the F225/F250. The Mercury FourStroke series 200/225 is at 475 lbs and the 250 is at 527 lbs. The Suzuki 200 is 529 lbs, and then either 606 lbs for the mechanical 225/250, or 639 lbs for the digital/fly by wire 250. Comparatively, at least for me in my particular situation, the F225 on the back of my boat weighs 583 lbs per Google. I've never had an issue with the weight, having her sit low or anything like that, nor does she really struggle to get up on a plane or anything else. That being said and as mentioned above, I wouldn't go any less in terms of horsepower, and honestly if I were to repower today, it would likely be the Suzuki DF250AP. She does weigh about 50 lbs more than my current setup, which I don't think would make for really any issues at all, but comes with a standard 5 year warranty, would likely be the cheapest out of all the other options, comes with the digital/fly by wire throttles, etc. And if I were to repower, it would definitely be with the digital/fly by wire controls as opposed to the mechanical ones. As much as I like Yamaha, especially the looks of them, their cheapest F225/F250 is just under $30k, and that's for mechanical controls. Their DEC/digital F250 is over $30k, some of them are even $35k-$40k per their MSRP sheet. Comparatively, you can find the Suzuki DF250AP for around $20k, and sometimes even less than that. To me, that extra $10k+ will buy you a considerable amount of extra fuel, or whatever else you want to spend on the boat instead.