Hi Josh,
Just for fun I dug out an old textbook and
estimate that a 1 1/4" through-hull opening about
3' and a bit below the waterline will allow 100-120 gpm into the boat.
The Rule 1200 gph hour is probably a lot less
after discharge head and hoses losses are calculated into it.
If anyone is really worried about emergency pump
I suggest a nice little gas powered pump. Of
course it probably will refuse to start when you need it! :)
Cheers, Russ
At 12:23 PM 1/15/2019, you wrote:
....
I'm preferential to a float type auto switch
wired in parallel with the manual switch. My
auto float switch is mounted above the pump and
only turns on when a considerable amount of
water accumulates. Under normal conditions I
manually pump the bilge down and the float just
catches it when I've abandoned the boat for weeks on end.
I have a check valve. There I said it. In a
perfect I world have a very high capacity
"emergency" pump and associated auto float
mounted just above the float for the lower
"normal" pump. The emergency pump would not
have a check valve. It would have a high loop
to avoid a siphon but nothing to prevent
backflow. It would also be as short and
straight of a run as possible to the
discharge. In this way I could ensure the
emergency reliability and capacity of an
emergency bilge pump by keeping it dry and
rarely using it. I would retain the normal
bilge pump's ability to pump the bilge to its
lowest reasonable level. Both would work automatically and manually.
The pump I have is 1200 gph (20 gpm) or 4 x 5
gallon buckets per minute - more flow than I can
move manually but not much. Once, I
accidentally left the transducer plugs out when
launching the boat. We discovered the
situation before water got to the floor boards
but not before a considerable amount of water
had made it in. Once the situation was
corrected the bilge pump continued to run for
what seemed like the better part of 5
minutes. The point being, 1200gph sounds
big... It isn't. If I had a shaft seal that
failed, the pump almost certainly would not have
kept up and that is the least catastrophic emergency I can think of.
Josh MuckleyÂ
S/V Sea HawkÂ
1989 C&C 37+
Solomons, MDÂ
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