Moeller Portable Fuel Tanks: Ultra3, 6BOW & Ultra6 Guide

Portable outboard tanks that look similar can have different capacities, footprints and hose-outlet arrangements. Moeller’s Ultra3, 6BOW and Ultra6 designs are not the same shape. Compare the actual tank dimensions and the original fuel cap before selecting a replacement.

Choose by shape and usable space

Ultra3 portable fuel tank3 US gal (11.35 L)
17 × 9 × 9¾ in unpacked

Compact rectangular tank

Compare part 620003LP
6BOW portable fuel tank6 US gal (22.71 L)
19 × 16½ × 11 in unpacked

Wide bow-style tank

Compare part 620040LP
Ultra6 portable fuel tank6.5 US gal (24.60 L)
21¼ × 13½ × 10 in unpacked

Long, narrow Ultra6 tank

Compare part 620049LP

All dimensions are manufacturer-listed unpacked exterior measurements. Allow additional clearance for connections and handling.

Do not confuse fuel capacity with tank footprint. The six-gallon 6BOW is wider than the six-and-a-half-gallon Ultra6. The Ultra6 also features a rotating fuel-withdrawal connection. Match the shape, not just the volume.

Moeller capacity and dimensions chart

MPN Component Capacity Unpacked dimensions (L × W × H)
620003LP Ultra3 portable fuel tank 3 US gal (11.35 L) 17 × 9 × 9¾ in
620040LP 6BOW portable fuel tank 6 US gal (22.71 L) 19 × 16½ × 11 in
620049LP Ultra6 portable fuel tank 6.5 US gal (24.60 L) 21¼ × 13½ × 10 in
305994-10 Two-stage replacement vent cap Replacement cap Match original fill neck

The cap is a replacement component, not a standalone fuel tank. Moeller’s current documentation lists the cap as a specified factory-style replacement for compatible Moeller/Tempo portable tanks.

Before ordering a portable fuel tank

  1. Measure the actual tank storage area and allow clearance for fuel hose, cap and lifting access.
  2. Choose 620003LP for the 3-gallon Ultra3 shape, 620040LP for the 6BOW design, or 620049LP for the 6.5-gallon Ultra6 only when suitable for the vessel.
  3. Check the original fuel pickup connection and the outboard manufacturer’s hose and fitting requirements.
  4. For cap 305994-10, compare the original fill neck and tank family, and follow Moeller’s two-stage venting and pressure-relief instructions.
  5. Secure the tank as specified and follow marine gasoline safety rules; do not install a tank in an unsuitable enclosed space.
Vent caps are safety components. Moeller 305994-10 uses a two-stage vent and pressure-management design. Use the correct cap for your tank and follow its instructions; do not substitute an unverified ordinary cap.

Compare Moeller fuel tanks and the replacement cap

Open each exact NewRVParts listing for product details and online availability.

Moeller portable fuel tanks

Two-stage replacement fuel cap

Related marine fuel parts

Need outboard primer-bulb hoses and a comparison with other portable tank sizes? See the Attwood tank and fuel-line guide.

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