Hi all brand newby I have krogen 42with perkins m135 I'm worried about exhaust temp at aqua lift muffler it's about three feet from engine but after several hours at any 1800rpm the temp seems to creep up to about 130degrees I think that's a little hot have owned boat over ten years dont remember it getting that hot have already looked at heat exchanger that looks fine my question is what's normal temp at exhaust