"The Happy Troller" by the idea developement co......spring loaded so when you pull on the line from front of boat, it flops down to slow the boat..if you see this ad ,i still have it

　　opening that fits over shaft is 6-1/2 x 2-3/4" actual plate size 8x10"

　　Small Troller Fits outboard motors from 20 to 50 hp.

　　A significant invention in the sport of troll fishing, Happy Troller mounts on the anti-cavitation plate to allow fine control of trolling speed. At cruising speed, your boat's stability is enhanced.

　　Happy Troller is the answer to correct trolling speed. Use it year-round in all boating activities; salt and fresh water.

　　Key Features:

　　Reduces troll speed in "down" position

　　Acts as a stabilizer in "up" position

　　Maintains stability in bow-light boats

　　Smooths out ride in rough water

　　Reduces porpoising and cavitation

　　Made of only highest quality stainless steel and marine aluminum; clear anodized aluminum finish

　　Installs in 15 minutes