Usually, when people attempt to make a case for prayer to Jesus being disallowed, they make the point that Jesus followed the example of ancient Israelites who only prayed to Jehovah. They point out that Jesus always prayed to His Father, and never to Himself. It's true that the Israelites only prayed to Jehovah;
Psalm 5:1-2 Give ear to my words, O Jehovah; consider my groaning. 2 Give attention to the sound of my cry, my King and my God, for to you do I pray.
Psalm 118:28-29 You are my God, and I will give thanks to you; you are my God; I will extol you. 29 Oh give thanks to Jehovah, for he is good; for his steadfast love endures forever!
Psalm 140:6 I say to Jehovah, You are my God; give ear to the voice of my pleas for mercy, O Jehovah!
And so they say that Jesus didn't come to change the established order apropos prayer, showing that this is the case by His example of always praying to the Father(e.g. Matthew 6:6, 9; 26:39, 42), and not to anyone else(including Himself); just as had been the case for the Israelites for centuries.
So, in short, their argument is this: Because the Israelites only prayed to Jehovah and never to Jesus(or anyone else), and Jesus Himself only prayed to Jehovah(the Father) and never to Himself(or anyone else), there is no reason to think that we should or can pray to anyone other than Jehovah(the Father).
All this, of course, rests on the presuppositions that the Father = Jehovah, and that Jesus ≠ Jehovah. So my questions are;
Is the Father ever referred to as Jehovah(or should I say Lord[κύριος/Kyrios], which can refer to both Jesus and Jehovah, since the word "Jehovah" never actually appears once in the NT) in the New Testament?
Do the Israelites ever call Jehovah "Father" in prayer(as Jesus called God "Father" in His prayer) in the Old Testament?
Is Jesus ever presented as synonymous with Jehovah in the New Testament?
Also, it might be significant to take note of John 17:11;
John 17:11 And I am no longer in the world, but they are in the world, and I am coming to you. Holy Father, keep them in your name, which you have given me, that they may be one, even as we are one.
If the Father gave Jesus His name, and Jesus' name is Jesus, wouldn't that suggest that the Father's name is Jesus and not Jehovah?