The tanks combined hold 25 gallons, 12.8 galls in the stbd tank and 12.2 approx in the port tank. If 25galls = 15" (height of the stbd tank) then by simple maths, 1.66 inches = 1gall. If you mark a wooden broomstick with 1.66" markings, you can easily use this as a simple dip-stick fuel guage via the fuel filler cap. Do not paint the broomstick because the diesel won't be able to soak in the wood and hence indicate the fuel level.
There are twin fuel tanks fitted behind the engine and infront of the aft cabin. They are screwed down fore and aft onto 2 wooden crossmembers. 2 bolts for each tank. Additionally there is a nut and bolt fixed horrizontally from a lug approximately midway along the top of each tank which fastens into the side wall of the engine/aft cabin compartment. You cannot see these and will have to be found by touch. The nuts are located in the fwd lockers of the aft cabin. Note the bolts are different lengths for each tank. Do not mix up once removed otherwise you'll find one will be too long, and the other won't fit! You will have to remove the engine compartment cover in the aft cabin to get at the nut and bolts and the interconnecting fuel pipe.
After draining the fuel tanks, disconnect fuel pipes, breather pipes and filler pipes and remove the tanks. Start with the starboard side tank first, sliding it out and turning it sideways as you remove it through the cockpit hatch. The port side tank is bigger so turn this on its side as soon as it's free then remove. Both fuel tanks have drain plugs underneath but they are difficult to locate and there is little ground clearance. Syphoning is suggested as the most appropriate method of draining the tanks.
Replacement is the reverse of the removal proceedure starting with the port side tank first. Fit the long horrizontal nut and bolt into the side wall before anything else. This is a 4 handed job. A long thin screwdriver or nail is needed to align the hole in the lug with the hole in the engine compartment wall. Push the bolt through the 2 aligned holes and get your assistant to screw on the nut and tighten up. This is fiddlely as there is little clearance and requires infinate patience! Next refit the starboard side tank.
It is imperative that the replacement tanks are exact copies of the original tanks otherwise the lugs won't fit, the filler pipe won't fit the hole in the cockpit floor etc., etc.
It is thought that the tanks were individually made for each boat. For guidance the following are the sizes for each tank.
Stbd Tank 10Â¾" wide by 22" long by 15" high. Fuel filler 5Â½" in from inner (long side) face, 8Â¼" in from aft face.
Port Tank 10Â¾" wide by 24" long by 11Â½" high + 10Â¾ wide by 11" long by 3" high on top at rear of tank + water/sludge trap on bottom of tank at the front 2Â¼" wide by 4Â½" long by 1Â½" high.
The author's tanks were originally made from mild steel and had lasted nearly 40 years. So the replacement tanks were made in mild steel were etched primed and then painted with two coats of a 2 pack external quality resin based paint.