Have you called Stewart? He has the molds and could tell you. When I was considering building a new 40 YB's, I measured the aperture and I think you could fit a 32" prop under it, which is a good sized wheel for that boat. Based off that, I would guess the aperture to be about 37"-38". On www.youngbrothersboats.com it lists the 40's draft at 46" and the 38's draft at 42". So I bet the aperture on the 38' is probably around 33"-34", which means you could fit a 28" prop under the 38'.
thanks powder, I just edited my post because I thought no one new what I was talking about (surprised) . good idea to call sw, also I'm surprised at the large wheel, that's good for me possibly, thanks again
The 38 Wesmac and 38 Lowell Brothers hulls will both accommodate a 28" prop, I think the NB 38 will fit a 30", and I think the 38 Flowers is even a little bigger. So the modern 38' downeast boats, from what I've seen, usually have 28" props under them. 28" is a good sized prop for that sized boat with 400-600hp. "Thorobred", the first 38 Lowell, had an 800hp MAN, and it had a 28" prop and hit 33 knots at sea trial. Are you thinking of building a new Young Brothers? Have you seen the picture of the new 40 YB that Stewart just popped out of the mold a few months ago? It was a beautiful blue color.