Hi all....... I'm having a strange problem that developed. I can fill both rear and forward tanks then leave Supply and Return on the same tank OR I can have the front tank empty, fill the rear, run everything to/from the rear but the forward tank will fill up & being smaller, it will start venting out once it;s full. Nothing has been changed as far as hoses since this started. The only thing I can see is these fuel management manifolds and possibly something going wrong inside If you look close (not the best shots, there are two vertical cylinders that might have some sort of valve inside? Something stuck? Two years ago just before the issue started, I had shaft packings going bad & they were leaking pretty good & over the winter (in the water), the power went dead for a few days & the bilge filled with a LOT off water, enough to short batteries and these manifolds were under the toxic soup. You are looking at the left side of the photo going aft, right going forward. Just out of the frame on the right are the four selector valves with port supply/return and same for stbd.Top hose is port supply, second down is generator and the smallest one on the bottom is the return line (I believe) There is the same set up on the opposite side for the stbd. engine. I'm completely puzzled........?????????? Any ideas? Thank you very much for your time!!