I suspect the question is not really serious. As a former owner of an Islander Excalibur, I can assure you that, while it is a very nice boat of its era, it is nowhere near suitable for a circumnavigation. Although it has a deep fin keel, drawing 4'11" if I recall correctly, it was fairly common for the keels to have play in them which would weaken the fiberglass all around the attachment point. The tiller/rudder assembly is another potential weak point. The outboard in a well is not a suitable engine and of course there is no signficant storage space for fuel or water and almost no electrical system. An autopilot or windvane would be very difficult to rig. Perhaps yours has been upgraded substantially, but neither the rigging nor the equipment would come close to a safe boat for the purpose. It was a very nice coastal boat, with modest amenities and a nice large cockpit. It was never designed or equipped for circumnavigation and the modifications that would have to be made are so major that it would not make sense to do them.