Speed difference and breaking hull speed
– Last Updated: Jan-25-12 6:34 PM EST –
First, I don't think any of the regular posters here ever use electric motors, so I doubt that anyone can answer your question about how fast your motor will be.
As far as the bigger motor being faster, yes, it will be faster. However, it won't get you planing like a speedboat. Instead, I expect that the speed will be in that "wallow in the hole" zone that's faster than hull speed but slower than planing efficiently. I once read about a fuel-economy experiment that someone did with a gas outboard motor on a small fishing boat. By far the best fuel economy was gotten at the lower end of the slow-no-wake speed, and by far the worst fuel economy was at "wallow-in-the-hole" speed with the bow high and the stern sunk deep (for those that wonder, the most efficient cruising speed was "just" fast enough to be planing cleanly). If it were me, I don't think I would want to waste battery power trying to go just a little bit faster while traveling at a speed that's already making the least-efficient use of "fuel". Perhaps the larger motor will run more efficiently at slow speeds than the smaller motor, but I only say that as a way of pointing out that I have no idea which motor will run longer when used "wisely". Still, my hunch is that the smaller motor is the better choice.