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Author Topic:   Automatic Pump Wiring
Smithsm posted 06-24-2008 09:51 AM ET (US)   Profile for Smithsm   Send Email to Smithsm  
I own a 1988 Outrage that currently has no bilge pump. The boat has twin engines with two batteries, mounted in black plastic protection boxes in the far rear of the boat on each side of the splash well. My plan is to install a Rule Automatic Bilge pump, without a separate float switch directly to one of the batteries. I am skipping the float switch because there is not a lot of extra space in the small bilge area and am concerned the switch might be interfered with by all the control wires.

I plan to use an in-line fuse and wire the bilge pump directly to one of the batteries. The larger battery is located starboard, closest to the bilge area. This batter feeds the starboard engine and the helm.

The port battery is only connected to the port engine. The batteries are not connected in any way. There is a "jumper wire" in the center console which I assume is there in case one battery needs to be connected to the other one to "Jump" it.

Would it be a good idea to wire the pump to my PORT side battery and thereby keep it separate from my helm wiring. this way, if the bilge pump were to drain my battery I would still have power to my helm and my starboard engine.

Any recommendations on size of pump ? I have read past posts and it looks like people use everything from a 500 to a 1500.

jimh posted 06-24-2008 10:07 AM ET (US)     Profile for jimh  Send Email to jimh     
It is a common practice to wire an automatic pump directly to a battery so that its operation bypasses all other distribution, switches, and fuses, and, in that way, the pump will always operate (as long as there is battery power) no matter how the rest of the boat's electrical system is configured.

Wiring directly to only one battery in a twin battery set up is a good practice in order to prevent the pump from pulling down all the batteries, if the pump should happen to run frequently or become stuck in the ON mode.

In a two-battery installation I am assuming there is a battery selection switch in the engine starter circuit so that the engine can be operated from either battery. In that case, it does not matter which battery you use to run the pump. Just do not leave the selector switch in the ALL position because then the automatic pump will be running off both batteries.

If one battery is dedicated to engine starting, run the automatic pump off the other battery.

As for the pump size, I believe the 1500-GPH pump was the typical model installed at the Boston Whaler factory on many models for which an automatic pump was an option. The pump was normally located in the cockpit sump compartment on the starboard side. In some boats there is so much rigging running through that area that it may be difficult to install a pump in there with all the rigging already in place.

Smithsm posted 06-24-2008 10:49 AM ET (US)     Profile for Smithsm  Send Email to Smithsm     
There is no battery selection switch.

sternorama posted 06-24-2008 04:00 PM ET (US)     Profile for sternorama  Send Email to sternorama     
A comment on pump sizing and ratings... the GPH figure specified by the pump manufacturer is usually at zero head pressure. Since you will have to push the water "uphill" to get it out of the boat, you cannot expect to see the performance as specified on the pump packaging. This could affect your pump sizing decision.

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