in stream floating micro hydro turbine

Hi just to let ye know am still doing trials on my floating turbine it s in 12 inch's of water flowing at about 3 ft a sec and there is 3 fins in the water at a time. It works great but when I increase the power it starts to jump the cogs .Will have to find a way of attaching a tension  cog to it [any suggestions would be appreciated ] once i get over this problem I will be able to let ye know the power i can get