Your 1997 boat has been in use for 22-years with two owners, so there is really no guarantee that all the systems involving plumbing, pumps, and hoses are in factory-original condition. Owner-modifications are not always improvements of the original design.
Re the two switches marked "washdown" and "water":
Generally a "washdown" switch would control a pump that provides water at high volume and pressure to a hose with a spray nozzle in the cockpit, for the purpose of rinsing the cockpit area. If there were such a pump, I would expect you would be able to hear it start up.
A switch labeled just "water" sounds like it would control a circuit feeding an on-demand automatic pump that would provide water at sink faucets when the faucet was opened. Energizing the circuit would not necessary cause the pump to start.
You have speculated both those could have been options. I dug up some information on the 1997 standard and optional features.
The 1997 Boston Whaler catalogue information for a 23 CONQUEST indicates a standard feature associated with plumbing, pumps, and hoses was a 1250 GPH bilge pump. This would very likely have been a RULE centrifugal pump.
Optional features associated with plumbing, pumps, and hoses were:
- Livewell with raw-water wash down
- Freshwater shower 20 gal
- Fishwell pump-out
- Marine VacuFlush head system with holding tank and overboard discharge
- Porta potti
- Porta potti with deck pumpout
I see a large Rule pump ...
By the term "large Rule pump" I infer you are talking about a RULE-brand centrifugal pump. RULE-brand pumps are very common on Boston Whaler boats. RULE pumps are normally found in the cockpit sump and used to pump water out of the sump and lift it a short distance to an overboard through-hull fitting. On the control switch they are often labeled as a "bilge" pump, even though a Boston Whaler boat does not have an open bilge space. Boston Whaler boats just have some sump areas. Usually the switch associated with a "bilge" pump has three positions: OFF-AUTO-MANUAL ON.
For a RULE centrifugal pump to have two hoses connected is unusual. Usually a RULE pump cannot lift water much distance at all into the pump intake port. A centrifugal pump usually has to be immersed into the water it is going to lift upwards. Also, centrifugal pumps don't like to work with too much head on the pump, that is, they don't like to push the output water very far vertically. The amount of head for a centrifugal pump on a Boston Whaler is usually limited to a foot or two at most.
I see a large Rule pump labeled as a wash down pump...
Q2: Is the label "wash down" on the pump itself?
Q3: Or are you referring to the label on the switch at the control panel?
I hear nothing running when either the "washdown" or "water" switch is activated...
If I understand your narrative, there is a pump labeled "wash down" but it does not run when the switch labeled "washdown" is activated.
Q4: Is that interpretation of your narrative correct?
Q5: Have you deduced which switch controls the RULE pump with two hoses?
...a male hose bib with cap on the starboard side of the engine well that has 1/2-inch poly line coming off it and disappearing under the deck heading forward.
This sounds like a water supply to the cabin area, as might have been used to deliver water to a sink faucet from a freshwater tank, or to supply raw seawater to a head for flushing.