3/4" hose vs 1" hose

[MLA]

Attwood Tsunami T800 pump. 3/4" inlet and outlet with 1" hose. 4:57 avg fill time.

Attwood Tsunami T800 pump. 3/4" inlet and outlet with 3/4' hose and 3/4 Fly High quick-connects. 5:11 avg fill time

Attwood Tsunami T800 pump. 3/4" inlet and outlet with 3/4' hose and 3/4 Fly High quick-connects and the supplied 3/4 hose-barb connection on the outlet of the pump. 5:25 avg fill time.

It seems like there was little increase in time going from 1" to 3/4" hose. Only 5% more time.

I'm planning to install a 3 pump system with reversible pumps feeding two 750s in the stern and one bow bag. Thinking one 1-1/4 thru hull to supply all 3 via 1-1/4 tube to 1-1/4 x 1 Tees to the pumps. I'm not worried about 2 or 3 minutes to fill or drain but would like to have a more compact install and 3/4' tubing between the pumps and bags would be a lot easier. Does anyone have a reversible pump system with 3/4" hose?

Another question: If I use 1" hose for the feed/drain hose do I have to use 1" for the vents? As long as I don't ignore water pouring out the side ports there is no danger of bursting anything, yes?

No you do not need to use 1" for the vents. I build all my systems with .75 vent

Also, when using a positive displacement pump like an impeller pump, you will see an even less increase in flow between hose and fitting size. But, I would go with 1" hose for the thru-hull to pump to sac plumbing rather then use a .5 male pipe thread x .75 fitting in the pump. Just slip the 1" over the barb and clamp.

Yes, a 1.25" thru-hull setup will support 3 pumps just fine.