Thread:

Another question for the PB brain trust

Drill for much larger fittings than you think you'll need and install shut off valves (approved for your specific type of fuel) at the tanks.

Leave enough room between the transom and the tank to service the cav hardware. Beyond that, let the flattie guys chime in about specific placement.

Don't want to leave you hangin...
Most Saddle Tanks in Flatbottoms are mounted where it makes the most sense in relation to the fuel fills. The picture below shows the fuel fill in the "standard" location...just behind where the cap turns inward toward the gunwale.
You say that you need to drill holes for the fills...if you have already filled them and want to do something trick....you can weld tubing to the tank and have the filler on the inside of the boat...works really well and you won't have to drill through the boat to mount the fills. The thu-hulls tend to move a bit and fracture out from the bolt holes...seen alot of nice paint messed up by the fills. If you decide to go through the boat with the fills..at least make a thin neoprene gasket to install under the fills or make a gasket out of clear silicone by spreadin a thin coat on the bottom of the fill and let it dry before installing. Oh..and don't go too heavy with the hose between the tank and filler...makes the fills too rigid which leads to the fractures from the bolt holes...think radiator hose type flexibility.
Also, CP Marine sells a real nice flush mount filler...they're pretty proud of them, but work and looks pretty good too.

1-1/2", 2" and 3" Billet Cam-Lock 1/4 Turn Fuel Fills - CP Performance

Originally Posted by JAFO

Dave,
How important will the balance be? Thanks for the insight on the "gasket idea" I hadn't though about fracturing.

With your engine at 35 1/2 inches off the transom(depending on where the strut is mounted), you will have no "hop" issues at 80-85mph.
Put the fuel fills where they look best on the boat(where it is flat), and as Factory1 says let the tanks fall where they may...
Set the plates flat off the bottom, leave your foot in the down(hopefully it has a downpedal) till the horsepower sets the boat, get off it and you'll be good(maybe with a tweak or 2 on the plates).

Originally Posted by JAFO

Dave,
How important will the balance be? Thanks for the insight on the "gasket idea" I hadn't though about fracturing.

After repairing all the cracks around my fuel fills I tried several things to keep the cracks from reappearing. Like Dave suggests I made some rubber gaskets for top and bottom to sandwich the fiberglass between the fill and a tapped 1/8 inch backer plate I made for the screws to thread into instead of nuts and washers. I drilled the holes in the hull slightly larger to allow for movement and I used a 3 inch piece of the soft silicone rubber they use for turbo couplings instead of the the radiator type hose. So far so good. Also I filled the holes that went thru the hull for the tank straps and made some nice blocks of hardwood with counter suck bolts sticking up to go thru the straps. I sealed them with resin and glued them to the bottom with a polyurethane construction adhesive by loctite called PL Premium. Home depot or dixieline sells it.