I don't know your boat specifically, but I have seen spreaders mounted to move and others not, so looking at the other spreader may not help. If you don't know how to tune your rig, hire a rigger and ask him to teach you, while you watch him.
The point of that, is that it is inadvisable that you go aloft to check out the spreader, if the rig is not tuned.
The rigger can answer your question about your spreader, as well. Sometimes it is really helpful to bite the bullet and hire a professional. What you can learn from them is certainly worth the price, IMO.