i have thru hull exhaust and i want dry headers.. how much more heat do they make if any and will they hurt my boat hull

I have been following your other post so I know why you are asking. Unless you are running a huge duration cam dry pipes are not nessesary. What is important are that you get long risers so the water is mixed further away from the engine. You need this to avoid reversion. Reversion is were the water from the exhaust is sucked back into the engine. For most mild performance cams this will work fine. Silent choice systems are not recomended for performance purposes. If it is to loud get mufflers. Hope this helps.

Dry exhaust on a boat does not mean what you think. Is is still water jacketed, and the water enters the exhaust stream at the very end of the tails. The headers do not make it dry, the tails do. I have a dry Stainless Marine stsyem on my boat, it does not get hot, as a matter of fact it is hotter sitting in the sun all day then when the boat is running. The problem is that it is very load, attracts a lot of unneeded attention. It was on my boat when I got it and is cut out through the hull over the swim platform, this is not how I would have chosen to do it, but cost too much to change now.

yeah mine are under the swim platform rather low