Mine has the auto float switch hard wired on, with a manual override.  Would agree safest option.

Really only use the override as a test. (Or if the switch float happened to fail)

At present my bilge pump is hard wired in via the float switch. Just I have a wiring job to do and thought I might change the bilge pump set up. Now to test I lift the floor panel and raise the float switch to switch it on, then I know both the switch and pump are OK.

the danger of a full auto permanent wired system (my boat has one also) that doesnt have a high level alarm-is that you wont know you have a problem until the bilge pump is overwhelmed and its too late.

The pump keeps cutting in until either the battery is flat or it cant keep up.

How would you design the bilge pump system?. Indication the pump is running, high level alarm.
Just again shows the importance of having fully charged, good condition batteries and plenty of excess capacity.

As rob said there should be a second set of normally open contacts on a bilge pump which has a high level float. These will only close when the high level float rises and can be used to supply power to almost anything (relay, indication light, alarm, etc..) 

the switch panel in the link looks as though it would run an indication light for when the pump is physically running, a light to indicate there's power at the switch, and a light to indicate a fault/high level. 

If your bilge pump does have a high level and second set of contacts and your handy you could probably fab up something yourself with an indication light and alarm   

Cheers 

Steve

How bilges are wired depends on how you use it (ie trailered or moored) trailered boats are easier in that there is always someone to operate them manually if required.

If moored the bilge should be hard wired direct to the battery that way you can switch off the battery switch reducing any drainage from the battery and still have the bilge kick in as water comes on board. Also some sort of alarm etc. as Rob mentions.

This all depends on wether there is someone present to hear the alarm and dependant on the state of the batteries having enough charge to run the bilge/s. Other factor is the ability of the bilge capacity to pump quicker than incoming water (some boats set up a second bilge at a slightly higher level so if water raises the second bilge kicks in.

If any of these factors are lacking then its only a matter of time until the water level reaches the tipping point (scuppers etc.). and the boat sinks. Most sinking's (on moorings) occur due to either bilge failure (including inadequate rated bilge) or battery becoming flat.

Also want to make sure any debris (including wiring etc) cannot be moved by water surge so as to jam the float switch up and flatten your battery etc. Best mounted with the float switch pointing backward or towards the wall/transom etc. so water surge can't break the float switch.

Off - off, manual - on/overriding float switch, auto - operating as per float switch.

Cheers

the terminology " hard wired " what that means is that the electrical device being supplied is not protected by fuses or circuit breakers , the only on shore equipment that is allowed to be "hard wired" is a fire pump I don't know of any of the vessels I worked on that had anything "hard wired" on them except the fire fighting pumps and the bilge pumps

OK getting back to 6m trailer boat! instead of a 40m trawler.
Indication the bilge pump is running, look left or right aft and see a stream of water.
Indication the pump is unable to cope, you're getting wet feet.
It would seem the basic essentials are as described by Jason P.
The more there is, the more there is to go wrong.

Been thinking a bit further and it seems that we are all over looking the crucial point here.
Whether we have bilge pumps (hard wired or not) and all the other paraphernalia, the essential element is that the boat crew are alerted that there is excess water (more than normal) in the bilge.
Once we know that, we can address the problem, put in the bungs, start bailing etc. Tackling the situation early rather than later when its too late could save the day.
Therefore an extra float switch sending out an audible and or visual warning is probably the most important., even before installing bilge pumps, remember a frightened deckie and a bucket is the best bilge pump.