Another potential problem with the two battery bank hookup is that under
certain conditions, both banks would be connected and if larger loads
demanded power but were isolated from their normal wiring and larger bank,
excessive current would flow through the bilge pump wiring creating
excessive heat and potentially, a fire.  That's the way it looks from here.

Good luck,

Bob Lowe
www.MV-Dreamer.com
www.CruisingAndMaintainingYourBoat.com

I don't like the two battery set-up, particularly since the feed to the
automatic is not protected by a fuse, so today's project is to replace the
on/off switch with a three position one and run both feeds off the house so
the circuit is protected properly, and to replace the pump itself - the
cause of the pump failure is a worn bearing that allows the armature to drop
off the brushes when the pump is in position, but allows it to run perfectly
when turned upside down.  With a single plank wooden hull, redundant pumps
are a must, but I need the security of knowing that they will work properly
when needed.

The joys of owning a 38 year old boat!

Bob Davies

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Thanks for the observation, Keith.  I hadn't thought of that eventuality,
but it makes a lot of sense to run the secondary off a different bank.
Whichever way I go, though, both positive feeds to the pump will run off the
same battery.

We hardly ever run the batteries down, because we run the genset for a short
time after anchoring out to make sure everything is charged (the genset is
on its own dedicated start battery that is connected to my 45 amp shore
power charger) just in case the engine mounted alternators fail.  I also
keep a portable power pack on board that has enough juice to start both
engines and the genset, so unless all three batteries fail at the same time,
we can still get back home.  The batteries are removed and stored at home
during the winter, so they receive regular maintenance all year.

Taid's Inn has three pumps.  The main is rated at 1200gph, the secondary is
750 gph, and the third is 500 gph.  If all three come on at the same time,
I'm wearing a life jacket and sending out a mayday call, because I've got a
BIG hole in the hull.  The main is large enough to maintain the water at an
acceptable level when she is launched in the spring, and the only time I've
seen all three running concurrently was when the morons in the marina
dropped her in to the water line without checking to make sure the drain
plugs were installed and flooded the cabin.  It really is amazing to see how
quickly water comes in through a couple of 3/4 inch holes and between the
planks before they swell.  They know better now, and I re-install the plugs
myself to make sure they don't forget while working through my pre-launch
checklist.  They are number 1 on the list.

One of the things I love about boats is that they keep your learning curve
high.

Bob Davies
-----Original Message-----

One thing to keep in mind: If you run the house batteries down to zero, the
bilge pump won't work any longer. My emergency bilge pump runs off a
starting battery, with the idea that if something happens and the house bank
is drained (maybe by other bilge pumps) this one will work when all else
fails.

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