Re: Docking with a spring line questions
I've had boats that spring in well on a breast line, and others not so much. I think the position of the line attachment on the boat matters the most. I'm thinking you need to attach further aft on your boat.
A sail drive might tend to position the prop a little more forward than on a traditional shaft log setup (since the prop can sit almost under the motor). Maybe this also has an effect because you are pushing from a more forward point....not sure, maybe someone with more experience with sail drives can chime in.
Also, the diagram looks like the boat is fairly full aft, so if you think about springing off from against the dock, you cannot pivot as much from amidships as you could in a more traditional design with more taper aft. But I still think it should work if you find the right point on your boat to attach the dock line.
You can experiment without damaging anything by slackening all the lines a bit and trying various breast line positions, until it does what you want when pushing slowly forward.