The following pictures are looking through the fuel into the tank (so there are reflections of the top of the tank superimposed on the image of what is in the fuel!) and show some kind of basket around the pickup tube at the bottom of the fuel tank. The sides of the tank appear pretty clean, however, the bottom has some black material which will need to get cleaned out this winter when the tanks are as low as possible.
This is a large dive flashlight pointed through the cleanout and then apicture taken. As you can see, there is a white spot at the bottom of the tank about the diameter of the "basket" on the end of the fuel pickup line. I suspect that this basket got moved in the sloshing of fuel around the tank and should be right on top of that clean spot.
I need to make sure that the pickup tube is going down into the tank as far as possible since this is the only fuel tank. I am planning on installing an independent fuel polishing system which will have a fairly large pickup going into a very large Raycor filter and an appropriately sized pump. The return for the fuel should be as far to the other end of the tank behind all of the baffles to ensure that the fuel moves through the tank.
This is another image. It appears that both the engine and the generator have these basket filters on the end of their pickup tubes.
Interestingly the return lines also go down to the bottom of the tank (or nearly so) which was probably done to avoid getting air back through the return line. All of the dip tubes have shut off valves (pickup and return).
This is definitely an area where I am going to have to work on upgrading the system to the more modern configuration with new filters, a low flow pump to keep fuel moving around and then a dedicated polishing circuit.
Unfortunately there is only one fuel tank on the boat. It might be possible to seperate the tank into two independent regions or alternatively add a "day tank" somewhere else in the boat and transfer fuel out of the main tank as needed which would avoid the issue of getting bubbles into the intake line if the tank is very low.