Depends what cruise you would like to be around, not sure what HP you currently have. You could probably go as low as twin 150's and as high as twin 250's. There are a ton of options out there for you, not sure if you prefer any brand over others. You also need to decide between 2 and 4 stroke engines.
You could stay rude/johnson and go with an Evinrude ETEC 200's would probably be nice.
Twin Suzuki 140's would be great on fuel, but probably too slow.
Twin F150 Yamaha's may be too slow as well but would also be good on fuel.
Twin F225 Yamaha's may be a good match, the F200's are the same weight so you might as well get the extra HP.
If you can find some leftover Yamaha 200 HPDI engines, that might be a very nice match as well.
Twin Merc Verado's might work also, there is a 4 and a 6 cylinder 200. The 4 might not push the boat as fast due to a smaller block, but would probably be faster then any 150's. The 4 cylinder will be better on fuel then the 6, but the 6 might be a better match for speed while also providing decent economy. I know some may say buy Opti's, but if I went merc I'd splurge for the Verado's.
Twin Honda's may do well also, they usually perform very well on Cat's, but they are a little on the heavy side.
I do not think you should have any major issued with weight, but I would first call Grady White and ask them what weight your transom should be able to hold, that may limit your choices. Also, before you repower, no matter what you decide to go with, have the transom checked, given the boats age it shouldn't have issues, but I've seen boats with wet transoms that are not that old. Since the engines will be removed, this is thew most convenient time to have this work done, plus you wouldn't want to spend a good chunk of change and then have transom issues. Once you do this, you can use your weight and HP limits to see what suits your usage best. If you want speed over economy, go with a high HP engine, if you would rather have better economy, a smaller engine may be better suited.
These days, all the engines on the market are fairly good, but the most important thing is to find a dealer you are comfortable with. Look for dealers who will be able to service your engines, make sure they have a good rep and that you will feel comfortable with them servicing the engines, this may narrow your brands down a bit and help in your decision. Good luck, let us know what you decide and some fuel number's after the repower would be awesome!!!
