I went back and searched the past posts but didn't really find what I was looking for so here goes. I'm finally putting together my GSO540 boat and I don't know if I have messed up or not. I made up the oil cooler lines using stainless braided lines and AN fittings to get the look I was wanting but I started to notice that while the lines that came with the motor as it was removed from the aircraft were -12 lines most of the other boats I looked at have considerably smaller lines. I'm using a fairly large Hayden oil cooler which I'm sure is larger than the planes original one so I don't think heat will be an issue but I've started to get concerned about the large lines leading to either lower pressure or the flow through the cooler being too fast to cool the oil. Just looking for some solid input from the commenters