pump questions

I plan on having my sacs fill and drain through a through hull. I want to get a reversible pump with an automatic shut off. Is there any reason i need vents? Can't I just make sure i shut the pump off before the sacs get too full? Also, when a reversible pump is off, water can not flow, correct?

come on quick simple responses are appreciated.

You will pop a sack or break fiberglass without a vent. Or both!

Reversible pumps will leak a little after they break in, but you can generally assume that there is no flow.

what is the easiest way to plumb a vent in? can i just run it to the hose for the bilge pump?

You can drain and fill through the same hole, it's the automatic shutoff that gets tricky. After running two impeller pumps for a season I won't run them again. Noisy, slow, power hogs. you already have one impeller on your raw water that needs service every other year, why add more when service free aerators work. Aerators work so much better, they just need to be plumbed correctly.

You should put a vent on the top side of the sack to release trapped air and pressure.

Everyone has there preference of pumps. If you have a rear storage locker and ski locker up front, you can easily run aerator type pumps, because they are hidden. If you have sacks on the floor, then typically you end up running impellar type pumps. Since you have a '90s Supra, I'm guessing sacs on the floor. If you keep an eye on the them filling you can get away without an vent. Typically once you fill and burp the sacs, you will not have any problem with trapped air.

I thought that the auto shut off was a run dry protection. Does it shut off if the pressure is too high too?