Tim R,
No, I don't have a shroud, but I did put a Dole-Fin on my 8hp Nissan and it made a huge difference, then, about a month later, I saw an ad for that shroud/thruster thing. Not only does it provide a fin with lift, it captures and directs aft the tip vortex off the prop, and I'm pretty sure I saw 30% in there somewhere, but it was a few years ago.
No, I don't have a shroud, but I did put a Dole-Fin on my 8hp Nissan and it made a huge difference, then, about a month later, I saw an ad for that shroud/thruster thing. Not only does it provide a fin with lift, it captures and directs aft the tip vortex off the prop, and I'm pretty sure I saw 30% in there somewhere, but it was a few years ago.