I have had a lot of experience with spotlights this past month. I use them in my canoe. On a boat, I recommend a 1 million candle light to run off your 12 volt deep cycle battery. I use 2 -500,000 candle power spots so I can look at 2 different places at once. I mounted the lights on a 6' pole. It works really well having the light elevated so the light can penetrate the water better and the size of the spot on the water is larger. I have been out 3 times with this setup and have killed about 30 carp and 7 gar. you will need to go very slow with your trolling motor stopping often or you will pass the fish without getting a shot. Another advantage to having 2 lights is that you can spot the fish with the first light, come to full draw, and shoot him in the second light. I also use a 130,000 candle hat light from Western rivers. It helps if you see a fish real close to the boat where the spotlights can't hit them.