Best Boat Gas Cap Assembly for Marine Fuel Fills

#1 · Best Overall

1. OUKENS Fuel Filler Neck

• Material: Stainless Steel
• Compatible with Vehicle Type: Boat, Yacht, Caravan, RV, Truck, Tractor…
• Weight: 0.35 kg

Best for: Keyless 1-1/2-inch deck fill.

Why it ranks #1: The listed 1.5-inch filler neck is a complete assembly-style option with 316 stainless steel and a built-in O-ring seal for marine deck fills.

A keyless cap paired with a 1-1/2-inch, 38mm deck-fill neck defines this OUKENS assembly for owners filling boat tanks or other listed vessels. Its mirror-polished 316 stainless steel and built-in O-ring address saltwater exposure and sealing across fuel, water, diesel, or waste applications.

The 316 stainless construction is described as rust-resistant with oxidation resistance, helping the assembly withstand harsh saltwater environments. A built-in high-elasticity O-ring provides the stated leak-proof sealing function, while the keyless cap avoids a separate key in the filling workflow. The listing names boat, yacht, caravan, RV, truck, tractor, and trailer use, and covers several tank contents. The 1-1/2-inch size remains the essential fit consideration across those applications.

Skip it if you need a cap with an included chain for a 50mm fill; KH866's 2-inch cap lists a chain and rubber seal.

This OUKENS assembly suits owners needing a keyless 1-1/2-inch deck fill for a listed fluid and vehicle type, with 316 steel and an O-ring. Match the neck size to your existing opening before choosing it.

Listed on Amazon as: Boat Gas Cap,1-1/2"(38mm) Gas Tank Filler Neck with Keyless Cap, Boat Fuel Cap, Marine Mirror Polished 316 Stainless Steel Hardware for Boat Gas/Fuel/Diesel/Water/Waste Deck Fill

#2 · Best 2-Inch Fit

2. KH866 2-Inch Deck Fill

• Material: Stainless Steel
• Compatible with Vehicle Type: Boat, Yacht, Caravan, RV, Truck, Tractor…
• Weight: 0.1 kg

Best for: Multi-vehicle 50mm deck fill.

Why it ranks #2: This 2-inch stainless-steel deck-fill cap includes a chain and rubber sealing ring, making it a useful larger-size option for compatible fills.

A 2-inch, or 50mm, size and broad listed vehicle range set this KH866 cap apart for owners seeking one deck-fill style across boats, yachts, RVs, and more. Stainless steel, a polished finish, a chain, and a rubber sealing ring address marine exposure and closure.

The polished stainless-steel body is described as rustproof and corrosion-resistant, supporting use in harsh marine and saltwater environments. A threaded cap and rubber sealing ring create the stated leak-proof connection for fuel or water, while the attached chain helps keep the cover with the fill during use. Its 2-inch/50mm size is the practical fit boundary despite the broad vehicle list, so buyers should match the tank opening to that specification.

Skip it if you need a 1-1/2-inch angled Perko fill cap; GYUTONG 0540DPG99A lists that application and its Perko figures.

Choose this KH866 cap if a 50mm deck fill suits your boat, yacht, RV, or other listed vehicle and you want a chained stainless cover. The stated size, not the broad vehicle range, determines fit.

Listed on Amazon as: 2 Inch/50mm Boat Gas Cap – Stainless Steel Polished Marine Deck Fill with Chain, Fuel/Water/Gas Filler Cover Replacement for Boats Yachts Caravans RVs Trucks – Deck Marine Hardware Accessory (Silver)

#3 · Best Saltwater Cap

3. TurtBluse 316 Cap

• Material: Stainless Steel
• Compatible with Vehicle Type: Watercraft

Best for: Saltwater deck-fill replacement.

Why it ranks #3: Its solid 316 stainless steel and rubber O-ring suit marine exposure, and it is listed as a replacement for Perko 1313/1314 and Seachoice 32011.

Solid 316 stainless steel is the defining feature here, giving bass-boat owners a corrosion-resistant replacement cap for marine exposure. Its 1-1/2-inch thread and stated compatibility with Perko 1313/1314 and Seachoice 32011 help narrow the fit, while the included O-ring addresses water intrusion at the fill.

The 316 stainless construction is specified to resist rust better than brass, a useful property for offshore fishing and extended exposure to saltwater. A precision rubber O-ring forms a watertight barrier against rain and splashing waves, helping protect the tank from water intrusion. The 1-1/2-inch thread and named Perko and Seachoice replacements make this a targeted swap rather than a universal cap; check that your deck fill matches those stated applications before choosing it.

Skip it if you need a cap for a different listed fitting; the GYUTONG 0540DPG99A instead names Perko 0540, 0541, 0556, and 0557 fills.

Choose this TurtBluse cap for a saltwater-exposed bass boat with a matching 1-1/2-inch deck fill and one of its listed replacement applications. Its stated fit is specific, so other fill models fall outside the supplied compatibility details.

Listed on Amazon as: 316 Stainless Steel Marine Deck Fill Cap with O-Ring,Replaces Compatible with Perko 1313/1314 & for Seachoice 32011,Boat Gas Cap Replacement,1-1/2" Thread for Bass Boats

#4

4. GYUTONG 0540DPG99A Cap

• Material: Metal
• Compatible with Vehicle Type: Watercraft
• Weight: 6.4 oz

Best for: Angled Perko fill replacement.

Why it ranks #4: This cap targets Perko 1-1/2-inch angled-neck vented fills and lists compatibility with figures 0540, 0541, 0556, and 0557.

Compatibility with Perko 1-1/2-inch angled-neck vented fills defines this GYUTONG cap and gives owners a clear replacement target. It lists Perko deck-fill figures 0540, 0541, 0556, and 0557, while an O-ring seal and proper venting address leakage and fuel-tank operation.

The specified angled-neck, vented-fill application helps buyers identify whether this cap suits their existing deck hardware before installation. Its O-ring is described as leak-resistant against leaks and splashing, which supports a better seal around the fill. Proper venting is also part of the design, so the cap pairs sealing with the vented-fill function rather than treating closure alone as the whole job. Its compatibility list is the key boundary for selecting it.

Skip it if you have another fitting pattern; Succell's 0540DPG99A listing also names Grady 263 among its applications.

This GYUTONG cap suits owners replacing a listed Perko angled-neck vented fill who want an O-ring closure that retains the vented application. The named figures define its fit boundary; use them to assess compatibility with your deck hardware.

Listed on Amazon as: 0540DPG99A Boat Gas Cap for Perko 1-1/2" Angled Neck Vented Fuel Fills

#5 · Best With Wrench

5. Succell 0540DPG99A Cap

• Material: Stainless Steel
• Compatible with Vehicle Type: Marine Vessel

Best for: Perko-fill owners needing wrench.

Why it ranks #5: The stainless-steel replacement fits listed Perko fill figures 0540, 0541, 0556, and 0557, and the package includes a wrench.

A wrench is included with this stainless-steel marine fuel cap, giving replacement buyers a tool alongside the cap itself. Its stated fit covers Perko figures 0540, 0541, 0556, and 0557, with Grady 263 also named, making the model list central to choosing this replacement.

The supplied wrench can support the replacement workflow without requiring a separately sourced tool, while stainless steel and protective coatings are described as corrosion-resistant for marine use. Compatibility with several Perko deck-fill figures and Grady 263 helps owners of those applications identify a potential match. Since the listing specifically names those models, this is a targeted alternative rather than a universal fit; confirm your existing fill falls within the supplied compatibility details before purchase.

Skip it if you need a replacement specifically for Perko 1313/1314 or Seachoice 32011; TurtBluse lists those applications for its 1-1/2-inch cap.

Pick the Succell cap if your vessel uses one of its listed Perko fills or Grady 263 application and the included wrench is useful for the swap. Its named-fit list remains the important boundary for other boats.

Listed on Amazon as: 0540DPG99A Marine Fuel Tank Cap for Perko 1-1/2" Angled Neck Vented Fills

#6

6. MEKILYN 0540DPG99A Cap

• Material: Metal
• Compatible with Vehicle Type: Watercraft
• Weight: 3.2 oz

Best for: Brass angled-fill replacement.

Why it ranks #6: This replacement is specified for 1-1/2-inch angle ventilation filling ports and uses a rubber sealing ring with a threaded closure.

Chromium-plated brass distinguishes this MEKILYN replacement, pairing a metal cap with stated heat and corrosion resistance for marine conditions. Its threaded closure and rubber sealing ring target leakage control, and the title specifies 1-1/2-inch angle-ventilation filling ports for a defined replacement application.

The threaded closure works with the rubber sealing ring to create the stated tight seal, helping limit fuel leakage during operation. MEKILYN says the chromium plating improves heat and corrosion resistance, relevant to a cap exposed to harsh marine conditions. The 1-1/2-inch angled-ventilation port specification narrows the fit to that style of fill, while the included housing is part of the package. Buyers should treat the angled-port dimension as the primary fit boundary.

Skip it if you need a cap for a 38mm fuel tank neck; Bitray HX2816 specifies tanks with 36–39mm diameters.

This MEKILYN cap is for a boat owner replacing a 1-1/2-inch angled-ventilation fill who values a threaded seal and plated brass construction. Its specified port style and size are the key fit considerations before selecting it.

Listed on Amazon as: Boat Gas Cap Replacement Part, Fits 1-1/2" Angle Ventilation Filling Ports

#7

7. Seachoice 32521 Cap

• Material: Other
• Compatible with Vehicle Type: Boat

Best for: Seachoice deck-fill replacement.

Why it ranks #7: A chrome-plated Zamak replacement with an O-ring and beaded chain, specifically listed for Seachoice deck mount fill plate 32041.

A beaded chain keeps this Seachoice cap tethered when open, helping prevent the replacement cap from separating from its fill plate during refueling. Chrome-plated Zamak offers stated corrosion resistance, while an O-ring provides a water-tight seal for the specified Seachoice 32041 deck-mount fill plate.

The tethered chain keeps the cap attached to the fill plate while it is open, simplifying handling during fuel filling. Its O-ring is intended to provide a water-tight seal when closed, and chrome-plated Zamak is specified for corrosion resistance in marine use. Compatibility is explicitly tied to Seachoice deck-mount fill plate 32041, making this a focused OEM-style replacement rather than a broadly specified universal cap. That named fill plate is the decisive fit check.

Skip it if you need a 1-1/2-inch angled-neck vented Perko replacement; GYUTONG 0540DPG99A lists Perko figures 0540, 0541, 0556, and 0557.

This Seachoice cap suits boat owners replacing the 32041 deck-mount fill plate cap who value a tethered closure and O-ring seal. Its specified plate compatibility is narrow, so other fill assemblies are outside the listed application.

Listed on Amazon as: Seachoice Replacement Gas Fill Cap, Chrome-Plated Zamak

#8 · Best Measured Fit

8. Bitray HX2816 Cap

• Material: Stainless Steel
• Compatible with Vehicle Type: Watercraft
• Weight: 0.12 kg

Best for: Keyed 38mm tank-cap fit.

Why it ranks #8: Its dimensions are unusually explicit: 44 mm cap diameter, 40 mm thread diameter, and suitability for fuel tanks measuring 36–39 mm.

Mirror-polished 316 stainless steel and an included key distinguish the Bitray cap for owners matching a 38mm tank opening. Its stated dimensions specify a 44mm cap diameter, 40mm thread diameter, and compatibility with fuel tanks measuring 36–39mm, giving buyers concrete fit points.

The 316 stainless steel is described as marine-grade and mirror-polished, with salt-spray resistance supporting continued marine use. The included key provides a keyed closure, while the stated tank range of 36–39mm helps owners compare the cap with their opening before installation. Its 44mm cap diameter and 40mm thread diameter add further sizing references. Manual measurement may vary slightly, so the listed dimensions are the practical boundary for deciding whether it fits.

Skip it if you need a broad 1-1/2-inch deck-fill assembly for fuel, water, or waste; OUKENS Fuel Filler Neck lists those uses.

Select Bitray HX2816 for a boat fuel tank within its stated 36–39mm diameter range when a keyed 316 stainless cap suits your setup. Compare all listed dimensions with the opening, since fit depends on those measurements.

Listed on Amazon as: Bitray Boat Fuel Tank Cap Marine Fuel Cover

#9

9. Ahuliao 621501-10 Cap

• Material: Plastic
• Compatible with Vehicle Type: Watercraft
• Weight: 0.05 kg

Best for: Manual-vent tank replacement.

Why it ranks #9: This vented plastic cap is a replacement for listed Moeller and Tempo tank models, but it is a portable-tank cap rather than a deck-fill assembly.

Manual exhaust for pressure balance is the central function of this Ahuliao vented fuel-tank cap, making it a targeted replacement for compatible tanks. Its plastic construction is described as chemically resistant, and the listing names numerous Moeller and other tank model numbers for fit checking.

The manual-vent function is intended to balance pressure in the fuel tank, a practical distinction for owners replacing a vented tank cap. Durable plastic with stated resistance to acids and alkalis supports use around fuel-tank chemicals. The extensive compatibility list—including 031103, 620003, and 730025—helps narrow the application, but the model numbers remain important because the listing does not present this as a universal cap. It is supplied as one vented cap.

Skip it if you need a stainless deck-fill cap for a 38mm opening; Bitray HX2816 specifies 36–39mm tank diameters and 316 steel.

The Ahuliao is suited to owners replacing a compatible manual-vent tank cap who need the listed pressure-balancing function and plastic material. Match the tank model numbers carefully; it is not presented as a deck-fill assembly.

Listed on Amazon as: Vent Gas Cap for Boat Fuel Tank Marine Manual Fuel Tank Caps Replacement Moeller Tempo Fuel Tank (621501-10)

#10

10. Eeyhooer Universal Cap

• Material: Acrylonitrile Butadiene Styrene (ABS)
• Compatible with Vehicle Type: Watercraft
• Weight: 3.2 oz

Best for: 12L and 24L outboard tanks.

Why it ranks #10: The ABS cap is described for 12 L and 24 L outboard tanks with an approximately 5 cm screw port, so it is least suited to deck-fill assembly needs.

Compatibility with 12L and 24L outboard engines gives this Eeyhooer ABS cap a clear use case beyond its generic “universal” title. Its approximately 5cm screw-port size, 51mm total height, and 70mm maximum outer diameter provide concrete dimensions for owners checking a replacement.

The ABS plastic construction keeps this cap distinct from the stainless-steel deck-fill options, while the listed 12L and 24L outboard compatibility identifies the intended tank sizes. Its screw port is approximately 5cm, with a 46mm inner diameter and 70mm maximum outer diameter; these measurements help buyers compare the cap to their tank opening. At 51mm tall, it is a compact tank-cap replacement, but the stated capacity range is the central application limit.

Skip it if you need a vented cap for a range of listed marine tank models; Ahuliao 621501-10 specifies manual exhaust and numerous tank numbers.

Choose this Eeyhooer cap for a 12L or 24L outboard tank whose screw port matches the stated dimensions. Its ABS construction and defined capacity range make tank and opening compatibility the key boundaries.

Listed on Amazon as: Universal Marine Boat Tank Gas Cap ABS Plastic Outboard Engine Motor Fuel