Although we have had some foreign customs officials look at engines and want lists of serial numbers etc., we have never had a US customs official look at the engine room--in fact the most "invasive" customs event for us was the having to throw away potatoes after a 4 year 40,000 mile cruise--when the San Diego Customs agent asked us where our last port was--(Cabo)--and the one before (Acapulco)--and where we had started from (San Diego)--not asking where we had been for the rest of the 4 years. I doubt that you will ever find U S customs inspecting the engine. Our last several entries into Pensacola was a cell phone call in on arrival and "come to the office in a few days" type of entry. Bob Austin