We really should set up a poll for the better way to do things 2D or 3D.... But!!! I may have missed what you meant,, The drawings above surely thos ar hand sketches not don in CAD at all... If So I admire you!!!

Give me a computer and a decenct cad package I can do anything.. Give me a Pencil and ask me to sketch..well,,, you might as well give the pencil to my grandson!!! i'm sure he'd do a better job.. I would give ANYTHING to be able to sketch.. I am VERY well aware of what sells a Mega Yacht and motor yacht I have all these ideas in my head for concept designs and no way to unlock them and put them on paper.. Doing this even in CAD is difficult to start with concept.. I posted some concept jpegs of Lady Lola , Ambrosiana And I think Pegasus yesterday.. I would love to be able to draw like that!! And if you can,, well youi got my vote.. Sorry i9f I miss understood.. Still cant make out wherte you stretched the line.. that 3D model above on my last reply would take 10 seconds to edit anything..Of coarse its not a yacht,,but its work.. only thing is I cant use my imagination now
As for Exhausts..I spent 5 years designing and building Avon Sea Riders... the big ones.. 6mtrs plus.. for all the VP engines we installed , I blanked off the exhaust port in the Out drive and fed it thru the transom... I love the sound.. 235 twin evinrudes on an 8.5 mtr searider sounds even better at full revs doing 75 knots.. but they are working boats not pleasure as you designing