bilge pumps & float switches ?

[sidelock]

I have a 1500 gph manual Rule in my 18 SF that is activated by a rocker switch in the instrument panel & after reading some concerning posts about sinking boats due to pump failure I have decided to install an additional second pump with a float switch or wire a float switch to the existing pump & install a manual pump as a back up.
The existing pump has a 1 1/8" discharge port & hose but the previous owner had it fastened to a 3/4" thru hull with a short piece of 3/4" hose inserted inside the larger hose as a reducer over the 3/4" thru hull barb & fastened with a hose clamp . There is good flow when activated but I don't know whether to leave it as is or go through the trouble of enlarging the hole & replace the existing 3/4" thru hull with a 1 1/8". I would also like some advice/opinion on what size & make pump & float switch to use.