75mm prop kayak drive

thingiverse

If you're not afraid to drill 43mm holes in your hull, along with a few screw holes, then you've come to the right place. I chose the Lifetime Tamarack/Tioga/Tahoma Muskie Angler - all the same hull mold, just different accessories. The Tahoma is the base model and sells for $170 average at Walmart's. They're 50 pounds, track beautifully, and are plenty stable, all made from roto-molded HDPE. Designed a propeller for maximum thrust on low RPMs. I used a Ryobi cordless circular saw motor with a 5:1 gear box. The output shaft spins 3000 RPM on 13V, so I needed a high-pitched propeller for the most thrust I can get from 3000 RPM. In the RC world, there aren't many - if any - propeller choices. This motor and prop setup matches what my 18-pound thrust trolling motor does on my kayak, with 3.5 MPH for 2 hours from an 18Ah battery. The 75mm was the most this motor wanted; it gets about 120F after 30 minutes riding, but doesn't get any hotter than that. On a static load, temperatures reached 140F, but that's the most load a motor will ever see, less stress on a dynamic moving test. Later on, I'll upload the housing I designed to install this into my kayak. The Ryobi gearbox has a 10mm shaft; I used a 5mm RC boat shaft and sterntube with an RC drive dog locking the propeller on. The stern tube OD is 8mm. The smallest blade propeller is perfectly matched for the 775 motor on a 5:1 gearbox that I'm using, and works well for my payload. With full weight in the water, including myself, fishing gear, and battery, the total weight this motor has to move is 260 pounds. It's putting out from 15-18 pounds of thrust, drawing 7 amps at full load. I'm controlling the motor with a 40A PWM controller off eBay for $10. My current battery is a $20 mower battery rated at 18Ah, so I've got 2 solid hours before the battery is low. The motor is rated for 18V; I imagine it would gain performance if run at 18V.