This is not at all unusual for even an 8 month old, especially a lab. They're a retriever, and can be a bit mouthy. Shouting often does not work, because they just think you're playing and it just gets them more excited.
Instead, when puppy bites, redirect to a toy and praise him for using it. If he insists on biting, end play. Step over a baby gate, close a door, whatever it takes to simply leave the dog. Play is done for 10-15 minutes. After the time out, you can try again. This method will teach the puppy that biting and getting overexcited results in an end to fun. This is not an overnight fix. It will take weeks, even months. Be patient and consistent, and remember dogs explore the world with their mouths. It's very difficult for them to learn how to interact with humans!