Thrust / horse power never equals speed. Not with cars,trucks, planes, or boats. Why is it a sports car with 200 hp can pass an 18 wheeler with 1300 hp? In cars speed is gained with gearing. In planes and boats it’s done with prop pitch. The pitch on a prop is the number of inches the boat moves forward for every revolution. If you are getting more speed with a bigger motor or multiple motors it’s because the original motor is too small for the weight of the boat and gear. The motor is over worked and cannot turn full rpm’s by itself. In the case of a trolling motor, this could cause over heating and hot wires or even a fire. In order to increase speed on a boat you need to increase prop pitch, but not so much that you reduce engine rpm as this will slow the boat. In order to tow another boat or push a log raft you need to put a lower pitch prop on. (called a work prop) The number of blades is also irrelevant A four blade 7 pitch prop will not go any faster than a 2 or 3 blade 7 pitch prop, but it will push a bigger load at that speed. (If it has enough engine or thrust to do it) because it bites more water, It will push or pull a bigger load provided you have enough horse power or thrust to handle that bigger load. That being said what makes anybody think the pitch on a 30lb thrust motor is the same as the pitch on a 55 or 80lb thrust motor?? More power means it will push a higher pitch prop. Trolling motors have little to no choice for prop adjustment. Hence the poster who got better battery life from a bigger motor got it because the smaller motor was overworked. Savvy?? Alaskan River Rat
