Saving Old Seagulls

I've been fiddling with and electric pusher for a canoe. The basics is wiper motor, stuck in a 75mm pvc T-joint with the shaft going through an oil seal. Tested my own home grown prop cut and bend from 3mm aluminium sheet. The prop is bend in more or less the shape I want it, it works great as a fan as well, but I get surprisingly less push from it than planned. Maybe some of you boffins have made your own prop to give me some pointers? There is still plenty of torque left, but I struggle giving the prop more pitch. I reckon I get about 3 pound thrust at the moment, and for the motor rating I should be able to get 8 pounds easily, enough for a canoe on flat water. The same motor was uses with a four bladed paddle wheel before that pushed a 2.4m plywood flatbottom boat. (Its called a "puddle duck", google it for plans.)
Oh and I know longer blades will be more effective, but I need the shallow draft.

Thanks

I dont think a 60w wiper motor is enough .....you get 75lb thrust per HP 746 w .....If you are interested look at www.boatdesign.net under An efficient electric boat ....