14 between wheels 16 and tiller drum 30 for selectively controlling the wheel speed of wheels 16 when handle 68 is in a first position the driving mechanism not shown residing in chassis 14 drives wheels 16 at a high speed in a second position the driving mechanism drives the wheels 16 at a slow speed such as one half high speed using gear reduction which is well known in the art finally in the third position handle 68 disengages wheels 16 from the driving mechanism altogether such that the wheels 16 are free to rotate and tiller 10 can be manually pushed thus each handle 66 and 68 has three positions providing distinct functions as described however it is noted that more than two wheel speed settings could be implemented and limitation to two speeds is not to be inferred a wedge member 70 is pivotally attached to a lower and rearward portion of chassis 14 between wheels 16 and tiller drum 30 member 70 extends vertically downward from chassis 14 beyond a plane defined by each skid 38 and into the lake bottom member 70 has a wedge portion 72 which faces forward when tiller 10 is propelled in the forward direction and is angled downward to urge chassis 14 downward when tiller 10 is propelled in either direction to keep each skid 38 upon the bottom surface of the lake by urging the chassis 14 downward when propelled each tine 32 tills a uniform depth of lake bottom to grub lake weeds as tiller 10 is propelled across the lake bottom since member 70 is pivotable about.