Jesus and Jehovah

I've always said Jesus is Jehovah. But as I studied I realized that Jehovah is nowhere to be found in the N.T. infact Jehovah is not even in the most accurate version of the O.T. the Septuagint (most quoted version of the OT by the NT) could this have been what Marcion meant by different God? Is this why Christ addresses God from the cross in Aramaic by the name El/Allah and not Jehovah (found in Matt and Mark which post date Paul's writings)? The scrolls of the dead sea do however contain Jehovah which could perhaps indicate Jehovah was a tribal name for God as opposed to a universal one. The New Testament writers themselves did not seem to place any particularly great importance on the Hebrew word, otherwise they would have certainly used it within the Greek text, as is the case with other Hebrew personal names mentioned throughout the New Testament, the tetragrammaton is missing in the LXX and NT. The only time it is seen, is in names and praise "Alleluia" ' IA' JA or YA. The fact remains the NT is using the Greek Isaiah, not the Hebrew. Therefore, there is no textual basis for replacing "Lord" or "the God" with what is presumed to be the correct rendering of the Name from Hebrew. There are no Greek manuscripts that contain the Tetragrammaton or a Greek equivalent. The J references are not manuscripts but translations of the Greek into Hebrew. None of them are earlier than the 14th century. Some even as late as the 20th century.