I had a mobile home and lot given to me. The mobile home has a fairly new 200 amp inside panel box with 100 amp service coming in from the power pole. It also appears on this Siemens 200 amp panel box that the 200 amp breaker is attached to the panel box. Could I snap in a 100 amp breaker on the power bar in the 200 amp box and run the service wire (from the outside power pole) to the 100 amp breaker and use the 100 amp breaker as the main breaker? Would this work if the 200 amp breaker remained in the box and I switched the 200 amp breaker to "off?" I hate to replace the box as I may be upgrading in the future.

Assuming that you mean that you have a panel with a 200 amp main breaker inside and also assuming that you have a 100 amp breaker on the pole, just use the 200 amp you have. The 100 amp outside will serve as your over load protection and the 200 amp inside will serve as a disconnect.only. Not need to change anything. Cable from pole to inside will have to be sized to fit breaker on pole anyway.

Thanks.