I've never been there, but I'm looking at the map right now... (I'd print it out and take it with you to the lake)
http://www.mass.gov/dfwele/dfw/habitat/maps/ponds/pdf/dfwhorn.pdf
in the hot summertime, those 2 mid-lake humps might be good for deep diving crankbaits, jigs, dropshot rigs, etc. There's that one just northwest of the island in 25-30 ft of water that comes up to 15, then farther south, there's one where it gets down to 30, then comes back up to 20.
The water drops very quickly just to the northeast of the island - quick access to deep(er) water is important, especially in hot weather. Often times(but not always, like during the spawn), where those contour lines are closer together, those seem to be better places.
This is pretty geeky - but hey, I'm a geek
- but you can print out a lake contour map and take a colored pencil and trace each line in a different color - 5 ft red, 10ft blue, 15ft yellow, etc. It makes it abit easier to visualize the changes in bottom contour and see features which may hold fish.
The natural lakes here in the north don't often have alot of bottom
structure, unlike the expansive southern reservoirs*, which are dammed-up rivers that flood the surrounding countryside - so
cover(weedlines, etc.) is sometimes all you've got to go on... so those mid-lake humps can be a
goldmine.
One thing you CAN try is using your sonar to find the deep edge of the weedline - that is, the deepest the weeds grow, which will vary depending on water clarity/sunlight penetration. That transition between weeds/bottom can be a form of 'structure'. If you find the deep weedline is say, 10 feet(for example), then follow that 10 foot contour until you find something 'different' which might possibly hold fish.
It's a guessing game - but the more we fish(and the more we learn about the fish we're after), the more educated those guesses get!
*Many years ago I had a VHS tape of Jimmy Houston on
largemouth bass fishing(smallies are a different beast) - and he said that most of the time, people should mainly concentrate on water 7 ft deep or less - which would immediately make the amount of water to search for fish, MUCH smaller. How that would work here in the north, I dunno... we have pretty much ZERO natural lakes down there, only ones amounting to small farm ponds of a few acres or less. Of course, our understanding of the fish has expanded exponentially over the years. That being said, a bass is a bass...