Ken,
Your conversion is pretty good and all I can offer is how to change it to
my personal taste. I did this conversion from your color image above. The steps I used are listed below the image.
Tim
1) Mask/Select the sky
2) Sky - Channel Mixer Layer: 100% Red 0% Green 0% Blue Set for monochrome (This helps to darken the sky)
3) Sky - Levels Layer: Change white input from 255 to 230 (This helps to brighten the clouds)
4) Inverse Mask/Selection (Time to work on the boat)
5) Boat - Channel Mixer Layer: 21% Red 63% 16% Blue Set for monochrome (This is my default B&W Conversion setting which I adjust according to the most dominate color - no need to adjust for this image)
6) Boat - Brightness/Contrast Layer: -5 Brightness +25 Contrast.
7) Good Luck.