  We present a search for outflows towards 51 submillimetre cores in Perseus.
With consistently derived outflow properties from a large homogeneous dataset
within one molecular cloud we can investigate further the mass dependence and
time evolution of protostellar mass loss. Of the 51 cores, 37 show broad
linewings indicative of molecular outflows. In 13 cases, the linewings could be
due to confusion with neighbouring flows but 9 of those sources also have
near-infrared detections confirming their protostellar nature. The total
fraction of protostars in our sample is 65%. All but four outflow detections
are confirmed as protostellar by Spitzer IR detections and only one Spitzer
source has no outflow, showing that outflow maps at this sensitivity are
equally good at identifying protostars as Spitzer. Outflow momentum flux
correlates both with source luminosity and with core mass but there is
considerable scatter even within this one cloud despite the homogeneous
dataset. We fail to confirm the result of Bontemps et al. (1996) that Class I
sources show lower momentum fluxes on average than Class 0 sources, with a KS
test showing a significant probability that the momentum fluxes for both Class
0s and Class Is are drawn from the same distribution. We find that outflow
power may not show a simple decline between the Class 0 to Class I stages. Our
sample includes low momentum flux, low-luminosity Class 0 sources, possibly at
a very early evolutionary stage. If the only mass loss from the core were due
to outflows, cores would last for 10^5-10^8 years, longer than current
estimates of 1.5-4 x 10^5 years for the mean lifetime for the embedded phase.
Additional mechanisms for removing mass from protostellar cores may be
necessary.
