The standard arrangement for control of a sump pump on a Boston Whaler boat includes a float switch.
The circuit diagram is shown in my article about sump pumps. See
COCKPIT SUMP PUMP
https://continuouswave.com/whaler/refer ... ePump.htmlGenerally a THREE-position switch is used. I don't understand your description as you only mention two positions, AUTO and MANUAL. Usually there is a OFF position.
The function of the control switch is really rather straightforward:
OFF--no electrical current is supplied to the pump.
MANUAL--electrical current is supplied to the pump, but this switch is a MOMENTARY CONTACT, that is, you have to hold the switch in this position; the switch will not remain in this position unless held; it returns to OFF as soon as you let go of the switch handle, and the pump stops running.
AUTO--electrical current is supplied to the pump at all times, but through a float-switch. The float-switch only passes current to the pump when the water level is high enough to exceed the threshold for the switch to close. This is called the ON-THRESHOLD. The float switch stops current to the pump when the water level drops far enough to open the switch. This is called the OFF-THRESHOLD. Generally in a well designed control system the ON-THRESHOLD and the OFF-THRESHOLD will not be exactly the same. If they were, the pump would tend to cycle on and off rapidly.
On the other hand, if you have a switch with only TWO position, AUTO and MANUAL, then the pump would have to be an AUTOMATICALLY operating pump that contained its own sensor for the presence of water. The switch would be left in AUTO and the pump itself would determine when to run. The purpose of the MANUAL position will be to override the automatic function and force the pump to run. Again, the MANUAL position will be a MOMENTARY CONTACT position. Also, I am quite certain that such a two-position switch would NOT have been installed by Boston Whaler in 1988; I don't think RULE made any automatically actuating pumps in 1988.
Finally, if the pump is not an automatically actuating pump, it makes no sense to have an AUTO position on the control switch.
Also, if you do install a float switch, there is very important consideration that MUST be given to where you place the float switch. Read my article linked above for a thorough explanation. You CANNOT just put the float switch in any spot you like and expect to have created a working system.