il_papa wrote:
Thanks Chuck, I have been leaning towards this solution while being
incredibly inactive at work today. Your suggestion of using a hose will
mean that I can really reduce the bilge level.

I have a very serious mechanical bilge pump which a previous owner had
hidden behind a bulkhead (that was a surprise I can tell you). I may
just use this instead and mount it in the transom and place a through
hole out the back of the stern.

The intake hose will be long though, can this be a problem? From what I
have read, it seems to be more important that the outlet hose is short,
which will be with this solution. Will I need to mount a non-return
valve on the intake hose?

Distance and lift both reduce the rated capacity of a bilge pump. The
farther you have to push or draw water and the higher you lift it, the
fewer gallons per minute you will actually pump. In your situation you
will not be able to avoid some length and lift, so be sure to install a
larger pump than might be "adequate" if your hose runs were short and
flat.

In my personal opinion, a non-return valve on the intake hose is
probably not necessary.
Yes, you will get some runback from the hose into the bilge after the
pump shuts off- but any restriction in the hose created by the mere
presence of the valve will reduce capacity.
Better a 1/4 of water in the bilge and a pump that might be better able
to keep a distressed boat afloat until some serious help arrives than a
perfectly dry bilge and a compromised pump.

Make sure to select a "self priming" pump for your application.