I have searched for many years for name of ship my g-grandfather Joseph Ecabert, age 28, farmer, came over on. He was from Switzerland. His passport was dated March 23, 1846. There was a cousin Joseph who came with brother Ignace in April 1847 and some have confused him with my Joseph. I don't know where he left from nor where he landed. I first found him in New Albany, Floyd County, Indiana in 1850.
Mary Lou - My first question is how you know that "cousin" Joseph is not your Joseph? I"m not saying you are wrong, but wondering if you have proof they are not the same man. Did you trace "cousin" Joseph to prove he was in a different place or with a different family at the same time as your Joseph?
Let's assume you have proof they are not the same person. With a surname like Ecabert you need to be very creative when searching. Use wildcards if possible. For example on Ancestry.com you can search for e*b*rt and that would pick up many variant spellings
Have you allowed a year or two past the date you have for his passport application? He may have arrived much later than you think.
Don't forget he might have come in via Canada and if he did you are probably out of luck as ships passenger lists to Canada did not have to archived until 1865.
Look for naturalization records if he naturalized. Some census years will give you that information. For example the 1870 census will show you if he was a citizen of the USA. If yes, you know he was naturalized.