your better off posting this in the saltydog forum. this question has been beaten to death over there.
strength, angle you should have it at, height vs. distance, want it to overlay on your GPS, ect. ect.
they work great in the ocean. we run quite a bit at night. we dont run an overlay as the gps breadcrumbs work better for navagation. mostly use it to track other traffic in fog and or dark and to look at bouys and shorelines to double check our posistion.
one thing to keep in mind a radar is finite, they will burn out with use, kinda like A.C. in a car, no set hours it just happens.
and you dont need a tower!, a pole will work great, ours is mounted just on top of the hardtop, about 9' above the waterline.