"He did a fantastic job". He has been fast all weekend.
"I think through the race I understood it. Speed-wise I think I know where it is".
However, the three-time world champion, who suffered with mechanical failures previous year when he lost the title to Rosberg, did not believe the issues were fundamental to the auto.
"We've given ourselves a lot to do but the whole team is focused on that and hopefully for the next race, we can start making progress", he said. "It has stopped Sebastian pulling away too far".
Starting at P3 just behind the two Ferraris, Bottas had a stunning start at Sochi, passing the slow-starting Raikkonen and then Vettel at Turn 2, taking the lead.
"I don't remember the last time we had that [overheating]", Hamilton said. So I was going to be fourth from very early on. I'm sure we'll go back to the drawing board and try to figure it out.More news: Things we learned from Trump's 100-day interview
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Hamilton arrived in Sochi as a two-times victor at the Olympic Park street circuit, a track where only his Mercedes team had won since the first race there in 2014, but he struggled to find his rhythm.
"That's why he won the race".
The result marks the 400th podium finish for Mercedes-Benz Power in Formula One and Bottas said: "It's going to take a while to sink in, normally I'm not that emotional but hearing the Finnish national anthem was very special for me".
So far success has alternated between the two teams, with Vettel winning the opener in Australia, Hamilton in China, Vettel again in Bahrain and Valtteri Bottas taking his career first success in Russian Federation for the team he joined in January.
"Both of them are fierce competitors and want to win races and fight for the championship, but I don't think it will affect the relationship and the dynamics within the team like it did in the last years between Nico and Lewis". But it's nice to get confirmation that the results are possible.
The 32-year-old Briton hugged Bottas in parc ferme, and latterly managed a smile and clenched fist for the cameras as Mercedes celebrated the Finn's victory in front of their garage after the race. Once we got round the first couple of laps I was basically stuck where I was. Vettel now leads Hamilton by 13 points. In his fifth Formula One season, Bottas now has a vehicle capable of fighting for regular wins and hopes Sunday will prove "the first of many". "Two weeks ago people were saying I am the number two driver but today it looks very different".