I have had good luck with the cheap 1100 GPH bilge pumps at Amazon. I wired in battery clips and just attach them to a deep cycle battery. (I think they are only $15, so I always have a spare on hand just in case you wear out the one you are using.)

I use them to transfer water from a tote on my trailer to the supply totes for the drip irrigation systems for the trees at my farm.

They work well for high volume/low pressure applications. I am only "elevating" the water by about five feet. I did test a brand new pump with a piece of PVC pointing straight up. The pump could lift fluid 10' but that was probably getting close to the max.

These pumps WILL NOT provide pressure. They will easily rinse off your kayaks like using a garden hose with no nozzle, but with a little less volume. You cannot add a nozzle and expect to spray off your kayaks.

That is my 2 cents worth. The cheap pumps are typically centrifugals. To get pressure, you probably need a different type of pump - which will necessarily be more expensive.