I heard a theory that there is contested evidence that the americas were partly populated before the berring strait existed and that small primitive boats were made that followed the coast line. Is there any true evidence suggesting this?
Tough to tell, though that is one possible interpretation of what we know today. Now, I should caution you that you'll want to consult an archeologist on this — my knowledge of the subject is based mainly on my interest in Beringia and Alaska.
What we're going to talk about is Chile. Specifically, a place called Monte Verde, 500 miles south of Santiago and 31 miles inland. Between 1977 and 1985, a team of archaeologists led by Tom Dillehay of the University of Kentucky excavated this site. When they dug, they found hearths, stone tools, worked wood, bones, ivory and the remains of animals. Radiocarbon dating revealed the layer at which the artifacts were found was put down about 12,500 years ago.
At the time, this was a big freaking deal. It was more than a millennium older than any previous settlement found to that point, and what's more, it was found in Chile. Think about that — it was not only older, it was much farther south than anything of that age. If people only came from Beringia, they would have settled farther north first, then moved south — and archaeologists hadn't found evidence of that. Needless to say, the Monte Verde find was enormously controversial when it was first announced.
Now, it's become accepted, especially with additional findings. That means we have a few interpretations: we can hypothesize that people advanced faster through the Americas than we previously thought or we can hypothesize that people arrived earlier in the Americas than we previously thought.
There is some evidence at Monte Verde for still earlier habitation — possibly as much as 33,000 years before present — but the consensus seems to be that those older dates don't have good artifact association and have been thrown out. There's other sites, too: a place in Pennsylvania that might have evidence of habitation 19,000 years ago, a site in Brazil that appears to have a shelter built 40,000 years ago (but now the consensus seems to be that it's a natural formation).
But back to your question. If we hypothesize that early Americans moved faster than we thought, the question then becomes how. There are limits on how quickly hunter-gatherers can move, but those limits change quite a bit if you bring water travel into the equation.
Before the strait existed, you wouldn't even need a boat. (The strait is the waterway.)
Could they have meant before the Bering land bridge? It came and went a couple times as ocean levels changed.