Manual pumps suck

They suck out the water just fine but most often you need to pump and brace all at the same time.  I find an electric pump is better for sit inside kayaks and have started bringing along the Attwood WaterBuster Portable Pump.  I took the weigh off the bottom of it so it is not so heavy and have mounted it in the front of the kayak wedged into foam between the front bulkhead and the foot pegs.  


If I come out of the boat I simply re-enter and turn on the switch with my foot.  I have it mounted so I can yank it back by the hose and help another pump out  if needed.  My hands are free while it pumps so I can move the boat to calmer waters.  The pump it a bargain at:


http://www.amazon.com/attwood-4140-4-Attwood-WaterBuster-Portable/dp/B000AP2XS2/ref=sr_1_1?ie=UTF8&qid=1328058099&sr=8-1

Sit on tops are inherently safe because the cockpits hold much less water and they are often self draining. In  spite of this they can get water inside from leaking hatches and cracks or small holes.  So this might be a good pump for you to bring on long trips or surfing days.  Many in your group will have the hand pump, but may want to try the Waterbuster if you have it.