Thread: Mainship 390
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Old 09-20-2010, 11:24 PM   #17
C lectric
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City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,414
RE: Mainship 390

It's is not unusual for two tanks to NOT empty at the same rate. Unless boat trim is dead even, the lines or hoses are exactly the same length and size, the arrangement and type of fittings are duplicated exactly there will be a difference in pressure or suction drop which will alter the draw from each tank.

And of course there are also the return lines, same problem.
There is no way to guarantee that level of equality.

A balance tube can be used but must be quite large, is not perfect and presents some problems of its own.

Sometimes tanks will be close by luck and some good planning.

Most of us will need to have a few valves that can be used to alter the fuel draw and more likely, the return.

On my boat it is the fuel return line valves that I use to even out the tanks. I don't shut them off, ever, but use them to throttle the return to force more to the tank I want. Once sorted out the settings should not need to be changed. This is one area that a gate or globe valve would be preferable to a ball valve as these valve can be adjusted in small increments.
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