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Old 08-11-2016, 07:09 AM   #1
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City: Norfolk
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Vessel Model: Mainship 400
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MS 400 Twin Fuel System

Does anybody know how the fuel system in a 400 twin works? All the documentation I have only addresses single engine. As I burn down I develop a list to port and haven't figured out why that is occuring.
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Old 08-12-2016, 07:05 AM   #2
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City: Carrabelle, FL
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Vessel Name: Morgan
Vessel Model: '05 Mainship 40T
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On our boat there is a crossover line with a cut off valve between the two tanks, it picks up on the aft lower midships corners of the tanks. The genset pulls from, and returns to the port tank. The Stb engine pulls from and returns to the stb tank. The port engine pulls from and returns to the Port tank. The fuel gauge sender is on the stb tank.

Odd that your boat lists to port, ours lists to stb if we put a lot of hours on the genset and pull the port tank down.

I've considered opening the crossover valve but haven't done it.
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Old 06-18-2018, 05:12 PM   #3
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City: Norfolk
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Mainship 400 Twin Fuel System

After doing some staring, experimenting, and screaming, it appears the Mainship 400 twin has exactly the same fuel system as the Mainship 400 single engine. With no means to shut down the crossover line, I can't isolate the engines to their respective fuel tank. In theory, each engine pulls from the tank on the side of the engine because there is less resistance. By the end of the summer I will put a valve on that crossover line.

That brings us to the list...

My theory was that the batteries and generator on the port side caused the list. As the boat sat in the slip the fuel would migrate by gravity feed from the uphill to the down hill tank via the crossover, causing the port list to increase while tied up.

Last year I moved the two 8D batteries to the starboard side for about a net 450 lb shift around the axis. List just about went away and doesn't increase in the slip any more. Also, fueling is much easier without "burping" the vent lines.
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