Your engine is mounted on an angle iron frame to allow the engine to slide forward using the mizzen halyard to take some, but not all of the weight. From memory you do not need to disconnect hoses or wiring and the engine will slide about four inches to allow you to slip the bolts and split the Vetus coupler. It is very very simple and easy to do.
If you have sheared a bolt I would think it is time to replace all four bolts and the new rubber bushes that are inside the coupler which are also Vetus parts.
I hope this is of some help.
Seafever of Cuan - For sale