First, find out exactly how deep your boat is. That info should be available online somewhere. Do a search on your boat and see what turns up. In a pinch, get out a tape measure and measure it.
Second, one foot of clearance is probably not enough. This depends on the tidal range in your area which is about 3.5 feet, and the exposure of the location to waves. With a particularly low tide and 1 foot waves you could be hitting bottom.
Third, your explanation of hitting bottom is accurate and to be avoided.
Fourth, the weight of the mushroom anchor
is only one factor of the entire mooring setup and the weight and type of anchor
depends entirely on the type of bottom and the exposure of the area. If it''s very exposed and you have to use fairly short scope I''d consider a Helix anchor
(very expensive, but less than replacing your boat). If the bottom is muddy use the heaviest mushroom you can afford, and provide enough chain scope to survive storms. If something really bad comes along you can move the boat to a safer location up the river or elsewhere (figure out where before you have to move). Ask other mooring holders in the immediate area what they are using, and what type of boat is anchored. DO NOT install the mooring in a channel or into the only deep path up a creek. You will irritate other boaters and you''ll have no peace as people pass very close by to stay in deep water. The train wheel mushroom would probably be ok except that it really is not shaped right - so you''ll need to depend on the extra weight.