Where are you located ?.
NO, NO trolling motor, do not make that mistake.
5 l/sec * 13 m * 9.81 = 637 GROSS WATTS, you may get around 300 NET watts
Get a small Turgo turbine at www.h-hydro.com and talk to Joe Hartvigsen @ joe@h-hydro.com and he will give you the best arrangement for your site.
4 inch pipe, sewer type will do ( lower cost) and a Brushless motor or a small single phase induction motor converted to the a induction generator producing the AC 120 Volts.
All well below 800 dollars, producing a lot of more power than a wind mill or the continuous expense of propane for the engine
And if you use the 20 meters and the 15 l/s you can get
20 * 15 * 9.981 = 2.943 KW GROSS Power and about 1.5 to 1.8 KW after the generator.
If you can use the additional power for anything else.
If you need assistance write to me directly.
Correct the address to remove the anti-spam
Nando