My friend put a custom ballast system in his 86 nautique and for some reason we can't get it right.
First, he built a custom (wood) box under the back seat for a fat sac and rigged the fill/drain pumps to it. I believe he has the inlet coming off a "T" with the intake for the engine. Then a fill pump, then a check valve, then a "T" with one side going to the sac and one going to the drain pump. The line going to the sac has an overflow that leads into the bilge exit that is obviously lower than the exit port.
We hoped that once the pressure built up enough from the sac pressing on the sides of the box that the water would go out the overflow and we would know to turn off the fill pump. Well, the sac bulges out of the box quite a bit without any water running out the exit port. We don't want it to burst in the boat so we turned it off before it got to that point.
Is this normal? and should we just build a more sturdy box that can take the pressure, or is there a problem with the setup?