Re: speedo and stumps
Depending on the size and type of your boat, the speedometer pickup is probably called a pitot, made out of an off-white plastic, screwed to the transom so the end of the tube is just below the bottom of the boat. It's like an oblique triangle pivoting on a base. It looks like a vacuum hose attaches to it that goes up to the speedometer.
Depending on what and how hard you hit, you may be able to just rotate it back into position. More likely, you probably broke either the pitot or the base it pivots on. You can get one at most boating stores for around $10. Simple to replace -- just remember to use some marine sealant around the screw holes.