Check out the information on this link over on the Whaler board. I am watching with a keen interest, as I am still running a 1989 Merc 200 carbed engine on my 1989 SC 23WA. I feel like I am running on borrowed time. I do all my own maintance, so I know what kind of shape the engine is in. I don't know that I have the weight issues that are discussed here. My rig was mfg for twin engines w/the large cut out on the transom. My fishing partner and I both usually sit on the rear access lids over the batteries.
I have 2 batteries in the rear and a 15 hp Honda for a kicker and carry the Honda fuel can in the splash well and I have never had any problems with water coming in the scuppers. I also have 2 Scotty electric downriggers w/10-15# cannon balls sitting on the transom.
http://continuouswave.com/ubb/Forum1/HTML/009809.html