that's my dream tool.
i've seen a guy with quite a small battery. i think it was off a motorbike. can't remember what he'd done to it but i think he had adapted it somehow. it powered a bilge pump.
trouble with a bilge pump is they are designed to move water but not at any pressure so the trouble is getting pressure for suction without screwing the bilge pump. water volume drops with head height pretty good too.
over time i've bought 3 different volume bilge pumps. they aren't all that expensive, the biggest was about $130 i think. smartmarine.co.nz is quite good for these. they also sell the spiralflex hose. this is easily coiled tight for transport in your backpack. helps to have some duct tape to keep it in a tight coil though.
i have a 550gph, a 1100gph, and a 200gph. the 2 smaller ones are the trusty rule brand, can't remember the brand of the 2000. the 2000 was a lot chunkier than the 2 smaller ones so not too good for hauling too far.
the trouble is each size will have varying hose couplings based on water flow.
bilge pumps are great for getting water to your sluice if you want to set it up out of the streamflow.
all that's generally needed is the bilge, a battery, some flexible hose, a hose clamp so the hose doesn't come off the bilge, a fuse to suit the size of the pump, some electrical wire of suitable size for the current used, and some clamps to fix to the end of the wire so you can easily connect/disconnect to the battery. a bucket is useful also to sit the bilge in so it isn't sucking too much silt and mud into it. bilges are pretty resilient to dirty water but you don't want too much crap going thru it. so just dig a little hole in the river bank and anchor the bucket down with some rocks.
in terms of the sucking to clean the bedrock/crevices i reckon those underwater riffleboxes are the go. keeping it all underwater retains the small power of the bilge. if you go and try to pump it all up a couple of feet you are going to loose some ability to suck those cracks out. i saw some good example of underwater riffleboxes on utube. they had perspex windows so you could see what was going on. it looked like the key was to keep the length of tubing as short as possible between the underwater rifflebox and the bilge pump, again to maximise any sucking power you will have.
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