What are the security effects of reusing a public RSA key to encrypt large data by blocks?
I assume that by 


  I want one side to do the encrypting but is unable to decrypt the data


you meant a general "encrypting only" party, since if you are talking about a specific piece of data, it does not make sense to disallow the encrypting party from decrypting that data since that party had the data already in the clear. 

If that is the case, then your goal might be achieved by first encrypting the data with a symmetric algorithm like AES, which can do big data rather efficiently, and then encrypt the symmetric key/PW with the RSA algorithm. That way, only the other party, who has the private key for the RSA algorithm, can decrypt the RSA-protected symmetric key and then proceed to decrypt the big data.