If the sticker on your boat says its rated for 400HP max, I don't think you can legally go past that number......the hull design and thickness is based on several variables including maximum speed....if its overpowered, it can potentially go faster than what it was designed for and cause problems......You should check the Coast Guard regulations on the HP rule...your insurance company may have an issue with it as well.
You will need a new bracket rated 500HP at the least.
May have to tie in the main stringers to transom, as now they are not. Check with a boat rebuilder on it.
depending on weight added, stern may be too low and you may get some water up the scuppers onto deck.
Thanks guys, I needed to hear this and kind of knew it but the price just kept sucking me back towards them I'll end up rebuilding what I have or looking for a good used pair of 200's
