A while back I was asking about where to get the weld on filler necks for custom made fuel tanks. Well after searching and not liking what is out there I decided to make some practice cuts with scrap tube on the lathe. The critical part of these tubes are where the fuel filler hose attaches to. They are ribbed (and not for her pleasure either, well maybe some chicks).  I set up my lathe compound and a carbide cutter bit to match the angle of the cut. I did this by eye.  As you can see in the picture I was playing around till I got the proper spacing of the ribs to come very close to matching the original on the original tank. It came out pretty good on the practice part. I am going to make a fuel tank for my Baja 18ES (mercruiser) project. The tank will reside under the rear seat. There was a small 18 gallon tank right next to the exhaust manifold in the bilge. Go figure. The tank I make should be around 35 gallons. I know it will not be USCG approved but I will follow all the USCG rules in building this tank and then some.  Hell, you should see the welds on the  tank that came with the boat. What a joke.