Re: bilge pump wiring -- mystery wire
If what you have been told is accurate, that one of the wires is to run it from a float switch and the other is for manual over ride then it should work when either of the two (red or white) wires is provided with power so long as the black is grounded. You tell us that it won't work unless both the red and white is provided with power. That tells me that the pump is defective. I would not use it myself. Bilge pumps are very inexpensive, why take a chance?<br /><br />Normal wireing for a bilge pump works like this:<br /><br />Most float switches have two gray wires. Most bilge pumps will have a brown wire and a black wire. The black wire from the bilge pump is connected to the DC (-) terminal on one of your batterys. Power is taken from your power supply, either at the battery directly (worst) or from the input side of your battery switch (best) and routed to one of the gray wires from the float switch, doesn't matter which one. The other gray wire from the float switch is connected to the brown wire on the bilge pump. That's all for fully automatic operation.<br /><br />Fully manual operation would have the black wire from the pump running the the DC - and the red wire from the pump running up to a switch, usually at the dash, which would supply power when in the "On" position. That's it for fully manual operation.<br /><br />To have both you first wire it as if for fully automatic operation but then you also run power from a switch and tie it into the gray wire from the float switch and the red wire from the pump, so that all three wires are connected.<br /><br />When you do it this 3rd way power is always available to the float switch so anytime it is activated by water in the bilge power is supplied to the pump. Also, even if power is not being supplied through the float switch (possibly becuause float switches are the least reliable boat part that I can possibly think of) you can still energize the system from your manual switch, probably located up on the dash.<br /><br />There is one other benefit to this and I recommend you take advantage of it - I have done it on each of my 3 bilge pumps and I'm happy I did.<br /><br />If you go to Radio Shack you can pick up little colored indicator lights for about three bucks each (or you can buy LCD's). If you mount one of these right next to your manual over ride bilge pump switch (probably on your dash board) all you have to do is ground one of the wires from the light and then run the other wire to the same side of the switch that has the wire going back to the bilge pump. If you do this what will happen quite naturally is that when you turn on the switch to power the bilge pump the light will also come on. That is nice because it tells you if you have left the switch on. However what a lot of folks miss is this, if the automatic float switch kicks on because of water in the boat it will send power to the bilge pump but at the same time it will also send power up the wire that goes to that switch. So your indicator light will go on if the float switch kicks on even if the manual over ride switch is in the "Off" position. That is to say the light will act as a warning light that you have water in the bilge and the pump is running. Not a bad thing to know about sometimes.<br /><br />Thom
<br /><br />Not a silly a question, and not an uncommon one here, either. The bilge pump can be operated in either a manual mode or an auto mode. One of the (+) leads would be wired to an on/off switch for manual operation. The other (+) lead is wired to a float switch for auto switching. There are other ways to accomplish the same thing with a single (+) and a single (-) so we dont see as many of the 3-wire pumps anymore. Hope that helps. 
