Steve,
You may want to ask the Gowrie Insurance group. At one point in time I did a Ensign charter boat (I owned the boat and chartered to another person). Gowrie was great to work with and helped me sort out how the liability worked with the charter agreement.
Partnership is a different agreement than what I did but they will likely be able to tell you what you need from a liability and insurance perspective - am sure they have many other customers with partnership agreements and can provide some advice.
Robin