The below furnished details is taken from http://www.dvaita.org/haridasa/songs/vadiraja/dash_stuti.html
It has been clearly stated that Gautam Buddha whom the Buddhists worship is not the incarnation of Sri Narayana.Even though many of his preachings were based on the preachings by Sri Narayana himself, but preachings of Gautam Buddha is similar to Advaita philosophy. If i have told anything wrong, that may be due to my limited intelligence, please feel free to reply so that i can let u know more abt the same.
There was a time, when the whole world (kaliyuga) was full of divine culture and vaidic (sacred) environment and at the same time many demons (asuras) were also born and started following the divine culture and learning divine knowledge. Because of this dharma started decaying (spoilt) in their hands.
During that time for the king of Shakya by name Shudhodhana a baby was born. It is understood that Sri Paramathma in the form of this baby started talking and preached that this world is void (shunya, empty) and all things which are happening are all miseries. This is suppose to be Bhuddha philosophy. (Sri Hari who is in the form of Baby has preached this).
In order to prove this philosophy is true to the people Sri Hari has swallowed all the weapons which devataas has attacked to the baby. After seeing these wonders and these incidents the King Shuddodaka and his followers started believing the new philosophy and started practising the same, by leaving aside the vedic philosophy.
After sometime the Paramathma who was in the form of baby has disappeared. and Shuddodaka son appeared again. Shuddodaka son grown up as Bhudda started preaching Bhudda philosophy which Paramathma has publicised previously. Even in Devaloka (adobe) Sri Paramathma has preached devataas (demi gods) the real essence of Bhudda philosophy which he has preached as Bhudda in this world. Sri Paramathma preached demi gods the essence of Bhudda philosophy which is publishised as 'Prashanthavidya' which even Shuddodaka's son Bhudda and his followers cannot understand this philosophy.
Sri Vadiraja is praying Sri Hari who is in the form of Bhudda to be kind to him by doing bhuddanjali.
Sri Vadiraja is praying Sri Hari who is in the form of Sri Kalki as one who is destroying (killing) wildered enemies and one who is wearing (holding) sword and shield and sitting on top of the pleasant horse. His body with all organs of the body are shining like splendour and Sri Vadiraja is praying that he is his own person who has to protect him.
PS : The original preaching of Bhudda philosophy was preached and publisised by Sri Narayana in the form of Bhudda. The preaching are meant in two ways. The original meaning was told to demi gods or devataas by himself in deva loka (adobe). But the sinful asuras or demons taken (understood) his preaching in wrongful meaning and started practising the same by blaming the vaidic dharama. Like this Paramathma will incarnate to get love from Asuras to Devataas has been told in Bhagavatha prathama scanda chapter 32 shloka 24.
In order to attract the Asuras who are enemies of devataas Sri Hari will incarnate as Bhudda as son of Jinana in the place called Gaya in the land of Magadha. This has been told in Mahabharata Tatparya Nirnaya Chapter 32 shloka 139.
Further, it has also been told that after completing 1000 years of Kaliyuga when all the devataas who were there in that yuga reached adobe and one who is killed by (destroyed by) Rudra by name Tripurasura was reborn in this world. At that time even Sri Vedavysa has disappeared and divine culture was existent by removing all faulty practices. At that time even demons had the opportunity to learn divine knowledge. But devataas and Paramathma did not like the idea of demons gaining divine knowledge. All devataas went to the ocean of milk where Sri Hari is residing and prayed him to bless them the solution for the above scene. During the same time in the place called Gaya (land of Magadha) Tripurasura was born to Shuddodana or Jinana. Paramathma disappeared the new born child and incarnated as a child. When Shuddodaka started doing ritual for the new born baby, the baby started smiling. They all stunned by the happening and the baby started preaching the new siddhanta called Bhudda sidhanta. Because of the prevailing situation ie divine culture they all did not believe the new philosophy, Paramathma remembered (called) his devataas and those devataas started launching different weapons on the new born baby. But that baby swallowed all the weapons like trishula etc and even when Vishnu attacked the baby with his discuss (chakra), even that the paramathma in the form baby made it as its seat and sat. On seeing the wonders of this child, Shuddodana and his followeres started believing and accepted the new philosophy by leaving divine culuture which they were following. After that the Paramathma disappeared from there and preached the real meaning of the new philosophy to the devataas, but demons were attracted by this new preaching and started following the same.
Even before this incident there is mention in Bhagavatha that Bhudda manifested earlier to attract Tripurasura's wives.
The Bhudda who was born during 3000 AD is not the incarnation of Sri Narayana. Goutama Bhudda is one who has publicised the Bhudda philosophy which was preached by Sri Narayana as a child. It should be assumed that Goutama Bhudda is not the manifestation of Sri Narayana.