If your outlets are smaller than your inlets - it is possible that even when you need max bypass, you still won't be able to get the pressure out. Always have you out be able to flow more than the in.

My philosophy is to always have the returns, bypasses, etc always bigger than the inlet, that way the regulator / bypass valve / etc can be set and it will work under all conditions.

At a minimum a -10 would work becuase you will never have 100% flow through the bypass ( I wouldn't go any smaller than a -10 for my system). 


I'm sure others will have opinions.

Every thing is the same size. Its all -10. The feed lines, the dump lines and the hull dumps. Also I never had a problem before with too much water pressure on my last set up on the same boat and it reved to 6600.It did have steel heads tho. now they are alum. Before it also had -8 water lines. and bassets . now Im running dry headers. Im assuming - 10 will be fine for the bypass as well. Im expecting the new motor to rev to 7500. wooo hooo.