S...
I put a SeaBuilt 8" access port in my H34' poly tank last weekend. GuyT's concern is a valid one. I removed all the diesel fuel from the tank first using the fuel polisher I built into jerry cans. I used the top gasket to draw the cut-out on the top of the tank. I wrapped a shop rag around the cordless drill and drilled a 3/8" hole just inside the circle to insert a jig-saw blade (saw also rag-wrapped) in and then cut out the opening. I used the top gasket again to mark out the bolt holes and drilled them out. I also then drilled a mounting hole for a fuel gage sender. I poked an enclosed shop drop light in the hole to see what mess was there to be cleaned out and found my fuel polisher pickup tube had ended at the deeped part of the tank, removing all fluids. The poly fuel tank is roto-molded so there's no baffles in them to be concerned about. I used a paint scrapper to scrape all the muck I could reach into one corner and removed it with shop rags, including all the plastic debris from cutting/drilling.Once the tank was cleaned I installed the fuel gage sender unit, closed up the access port, and pumped the jerry cans back into the tank, repositioned some fuel lines, bled the system, and fired up the engine. A half hour later the filter vacuum gage had hardly moved. Piece of mind -- PRICELESS!Pictures still in the camera--will post later in the week. If you are the least bit skilled mechanically you should be able to do this with ease. The SeaBuilt product is great!