I have a Spirit 1.0 Plus and a 7’7” Achilles inflatable keel dinghy.
It is wonderfully easy to mount that motor on my dinghy in the water. I first load the motor section and battery separately into the dinghy. Then I mount the motor section on the transom. When that’s secure, I install the battery on the motor. They are about equal in weight and easy to handle in that little dinghy.
I’m pleased with the performance of the Spirit 1.0 Plus, but I’d be surprised if you could achieve 4 knots at half-throttle with three adults aboard a 9’ inflatable. However, at your stated 20-30 minutes of daily use, you could likely achieve 4 knots loaded at a higher throttle setting that will stay within battery endurance.
I’ve only used the Spirit on my dinghy to motor to shore and to other boats in an anchorage. I haven’t tried to measure speed achieved and I haven’t made any extended trips. According to the battery life display on the Spirit’s tiller, battery endurance rises exponentially as one uses less than full throttle. Hopefully, someone can provide an apples-to-apples comparison.
I love the silent operation of the Spirit 1.0 Plus. Other boaters in an anchorage have commented on how quiet it is. The noise of the dinghy going through water far exceeds the noise of the motor. Also, it’s nice not having to carry a fuel supply for the dinghy motor.
