Hi Peter
The scoops I use are pieces of copper tube bent (using the groove of an old flywheel) in a compound curve wherever in the hull you want them to exit.
Buy some copper brake tubing from your local brake tube maker (friendly garage) then cut off the required length + 50mm. Heat is up with a blowtorch until it changes to a lightish pink colour (you will have to move along the tube bit by bit), then let it cool (this is called annealing). The tube will now be soft enough to bend with your fingers. Put the tube in the groove of your flywheel about 50mm from the end (hence the extra 50mm) and bend it to about 45 degrees. This will give you the bit that sticks through the hull. I then usually run the tube along the bottom of the inside of the hull to the point where I want the inlet. Remember that the bit you've already bent will be pointing forwards then just bend the rest in the direction you want to go. Pic 1 below shows two tubes going forward from either side of the shaft to the engine bay (excuse state of boat, I don't run that one anymore)). Pic 2 shows the positions of the scoops under the hull.
The inlet needs to be positioned where it will be in the water ALL of the time (unless you're doing salmon impressions)
usually towards the transom, but work out if anything will be in the way first.
Leaving enough room for the bend in the inside, drill a SMALL hole in the hull (I use a 3mm drill) then turn the boat hull upwards. Using a round needle file at 45degrees to the hull (hole pointing forward remember)
, open up the hole until your tube is a snug fit.
Insert the tube and tape the inside piece to the hull bottom (not at the exit hole though) and glass the tube in at the exit point. glass the front end in and leave to set.
When thoroughly set, cut the inlet tube as close to the hull as you can at about 80 degrees (not critical, for less drag, I've seen them cut flush with the hull, but as your's is not so critical, I'd err on the side of caution)
Job done
I like to put my OUTLET so that I can see the water jet when the boat is running, then I know it's not blocked, but that's a personal choice.
Pic 3 is the slot in the rudder type which is just as efficient (at high speed) but more fiddly
and is usually built in to the rudder.
Hope that helps
Danny