Is the boat an 89 or 99, if an 89 that weight will really be pushing what I would safely add, going from a carbed 225 Evinrude to a 200 HPDI on my 1989 22, my boat sat lower, maybe 1/3-1/2", but I still feel safe, if I added another 100lbs of engine before my crew, I might think again, it would surely be safe, but not how I'd want the boat to sit or feel in the water personally. To me, any open transom boats older then late 90's should refrain from 4 stroke power unless their really is no other option, a rebuild would be a better choice if an option.
If your talking 1999, then here are my taughts.
Going from a 6 cylinder to a 4 cylinder if that is the 200 verado your going with will be a considerable drop in power due to less cylinder's, in rough seas or under heavy load the boat will fall flat on it's face more then likely, or put more strain on that super to produce the power it needs to run how you'd want, a 6 cylinder would give you better power, but will weigh a bit more. Best way to simiulate it is to add the additional weight of the repower in sand bags, but add a little more, the location of the weight ina 4 stroke hangs off the boat more then a 2 stroke typically, not sure why but it does so account for that also. I would not go below 200hp, and a 200hp 4 cylinder 4 stroke would really be pushing it, the 6 cylinder 200 would be good power but might cause weight issues, would be close. I think it also depends where all the other componenets will be located, can they be moved forward a little or will they all likely be under the back well area?
Check with Grady at the factory as to what your boat can handle weight wise, you should be able to handle the weight if i am correct, but not sure how the boat will actually sit, depends what your comfortable with. If you fish in rougher conditions, the extra weight might be more noticable on the drift, if you don't go out in that typically, it may not matter as far as how the boat sits. Do you have plastic nylon thru hulls or are they SS or bronze? If they are plastic nylon and the boat will be sitting lower where they will touch the water, I'd highly advise replacing them as well. From the looks of your picture, it looks like your already at your scuppers, the 4 stroke if going with the 6 cylinder, will likely bring it down as much as half an inch more, only way to really tell is added the weight and then put 2 guys in the back to simulate as if your fishing, also compare it before with 2 guys to get a feel both ways. If you really can, have someone on the dock also take pictures to give you another perspective, those pictures might show you something you might not see or notice from inside the boat.
