Pronunciation of おう: long sound (chouonpu) or two separate vowels


**Google Translate** 's pronunciation for the word 思う sounds like /omou/ with
two separate vowels sounds /o/ and /u/ at the end:

[https://translate.google.com/?sl=ja&tl=en&text=%E6%80%9D%E3%81%86&op=translate](https://translate.google.com/?sl=ja&tl=en&text=%E6%80%9D%E3%81%86&op=translate)

However, I learnt that for the _もう_ , we should pronounce this part with a
single /o/ with a longer length, like /o:/, so it should be /omo:/ instead of
/omou/.

Is Google Translate's pronunciation incorrect in this case or am I wrong?

