Can anybody help me answer a few questions?

I am curious what Engine Manufacturers are popular and what Engine
Models are common in the US?

Also how do people usually service or repair their engines?
Where do you take your boats for service/repair?

My situation is this. Currently my family provides spare parts for
Marine (ship) Diesel Engines, but mainly in Asia. I would like to
setup an office in LA but I do not know enough about the Marine Diesel
Engine market in the US. Do you think you could help me answer a few
questions regarding Marine Diesel Engines in the US?