How long does it take for shipping manufactured goods from China to US via sea?

I'm trying to get the first batch of my product from China to the US. The products are not enough to fill a shipping container, but will be too expensive to do airfreight.

How long does Ocean freight take from China to the US?

Including time getting goods on the ship and off the ship, about 4 weeks via ocean to West Coast of the US.

It depends on where in China the goods originate and where in the US they need to arrive. As Dan says, from port to west coast port, you're looking at about 3-4 weeks.

You say that you don't have enough to fill a container, which means LCL shipping, this will add in extra delay at both ends, as the forwarder will wait until the container is full before shipping, and will need to separate the load upon arrival. This could add as much as 2 weeks in total.

Delivery from the West coast could take several days, or longer, depending on how far you need to rail/truck the stuff.

Lastly, you're also at the mercy of Customs. If your paperwork isn't good, your product is something of interest to them, or your container gets pulled for inspection, you can add another few days at least, a week easily and potentially much longer. Expect to pay storage costs if this happens.

Talk to your forwarder, they'll be able to give you a more accurate estimation based on your needs.