I have a 1995 125 hp mariner it has 4 carburetors on it. Are the 2 bottom carburetors for low rpms and when I go wide open on the throttle do the top 2 kick in. Or do they work all together at all times. I just can’t seem to understand how this works. I am planning to start to do my own work on it and trying to learn as much as possible. I got the seloc repair manual which I am going thru. I would appreciate is someone could explain this process for me. Thank you very much.