The drag on the shaft, or close enough that it doesn't matter, is the same whether it is 100 mm vertically or angled over a meter to get to that 100 mm depth.

The primary problem though is the penetration through the surface of the water. The drag there is much worse than it looks like.  There is a very good reason a lot of work and effort is put into attaching rudders, props, keels etc to the hull underneath the boat.  Wing root drag is minimal compared to the surface interference drag and ventilation. It is much cheaper, easier, and less maintenance to simply stick the appendages through the water, the only reason for going to all the trouble of mounting the stuff on the hull under the water line is to decrease drag.  Eliminating that minuscule surface drag must be important to at least a few boat manufacturers, so at least a few people agree with me.

About the weeds, a fouled prop is horrible.  Rain cuts some airplane propellors efficiency by 15 to 30%. The more critical the surface the worse the effect. I don't have a good solution for the weeds. The prop itself creates negative pressure that sucks the weeds and lines in.

If the weeds are primarily floating on the surface though, eliminating the two surface penetrations might help a little, the shaft might be steering weeds straight to the prop. Putting the shaft in an aerodynamic keel might help.

Talador

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