I've taken this back to just single post to rec boats building .... Someone
else can cross post it if they wish.
I'll start off the straw poll.
I've had two float switch failures and one pump failure.
My other comment is that I'd never put the float switch after the pump, that
makes the pump and both wires to the float switch permanently live. If the
float switch is first, it's only the wire to the float switch and the switch
itself that is live.

A previous owner of my previous small clinker fishing boat had wired it pump
then switch. And the wires ran through the bilge water. Insulation
breakdown on the wire from pump to switch. This resulted in electrolytic
attack and complete destruction on several copper nails in what I think is
called the cover strip - at any rate nails which had been long enough to go
well down into a very old keelson. It didn't quite sink .... After this
was all fixed up, and new pump etc fitted, the boat still leaked. Turned
out the electrolysis had also eaten away most of the 3/8" dia copper engine
bed bolts. By the time we had fixed all this and a few other things we were
pretty good at getting the engine out - the record was 20 minutes!.

David


"Pete C" wrote in message
news
On Thu, 26 Jan 2006 12:22:02 +1100, "David Flew"
wrote:


Not a bad idea to have a 'basket' over the pumps and float switch.
Also two pumps running off one float switch gives some redundancy.

IMHO the best way to go is a float switch and two small pumps, then
higher up above normal bilge water levels another float switch and
much larger pump. Ideally run each off different batteries.

cheers,
Pete.

I agree about the basket, if you have enough space. I don't, and mesh
which
is small enough to protect the pump from debris soon blocks up with gunge.

A strainer over the pump and switch made of 5mm sq stainless mesh
should do (I have a bird feeder made from the stuff)

The Johnson float switch has an in-build strainer, so it's OK, and I just
have to regularly flush the bilges and be careful about housekeeping when
I'm doing carpentry on board ...

I've doubts that having two pumps off the one float switch makes things
more
reliable. If either jambs, it would blow the fuse .... If you have
separate fuses for the two pumps, you still need a larger common fuse to
protect the switch and wiring.

I'd have two fused lines each feeding one pump +ve, then the -ves from
the pumps connected together and going to the float switch and back to
battery -ve. The on/auto switch would just go in parallel with the
float switch.

Also it seems the 1000 gph pumps seem to use the same casing as a
500gph pump, but cost almost twice as much. So for the price of some
extra hose and an extra outlet you can have 2 500gph pumps instead of
a single 1000gph one.

IME the pumps themselves fail in other ways rather than just jamming,
on my previous one the shaft snapped. So in that case 2 pumps would be
much better than one. Even if one gets partially blocked, the other
will work and lessen the rate the battery is flattened.

Maybe a straw poll of bilge pump/float switch failures would be
useful, can anyone else comment?

cheers,
Pete.

David