Diesel quality, dock etiquette, the provisioning reality, and filling the water tanks without contaminating them.
Marine diesel is more expensive than highway diesel because it arrives at the marina by barge, truck, and storage infrastructure that costs real money to maintain — and because the marine fuel market has relatively few buyers competing among relatively few suppliers. The price differential varies by region and season, but expect to pay $0.50 to $1.50 per gallon above what the gas station around the corner charges for off-road diesel.
Gasoline at the fuel dock carries similar markups, and in many coastal marinas the mix is ethanol-free marine gasoline — which matters for outboards, generators, and older carbureted engines but costs more per gallon than the ethanol-blend at the pump. If your boat uses a lot of gasoline (large outboard tenders, gas gensets), factor this into your provisioning calculations.
The additive question divides the cruising community, but the practical consensus is: treat diesel that will sit in a tank for more than a few weeks. Diesel algae (actually a microbial growth, not technically algae) forms at the fuel-water interface in your tank and produces the black slime that clogs fuel filters and injectors. Biobor JF at the standard dosage — 1 oz per 32 gallons — is the widely used preventive. For diesel stored over winter or for more than 60 days, a fuel stabilizer like Sta-Bil 360 Marine addresses oxidation as well. Neither product is expensive relative to the cost of a blocked injector or a fuel polishing job.
The fuel dock is often the busiest, most time-constrained part of a marina. Other boats are waiting. The dock attendant has been doing this since 7 AM. Do not arrive at the fuel dock and then figure out your approach; have your boat ready, your dock lines coiled and in hand, and know which side you're taking fuel on before you're within fifty feet of the dock.
Before the attendant opens the fill port, tell them: the type of fuel (diesel or gas — never let them assume), your approximate quantity, whether you want a fill or a specific number of gallons, and whether you're paying cash, card, or marina account. If you have multiple tanks, tell them now — "port and starboard, both diesel, fill them both" — not after the first tank is full and the hose is already put away.
The fill-up vs. top-off question has a practical answer: fill to capacity when you're departing for a passage, particularly if the next fuel stop is uncertain. For short hops between marinas with reliable fuel, topping off at every stop is fine but wastes time at busy fuel docks. One approach: fill tanks at the beginning of a cruise leg, top off at the halfway point if you're more than halfway through your capacity. Never run tanks below 25% if you can avoid it — settled sediment near the bottom of the tank gets stirred up in a seaway and goes straight to your filters.
Credit cards are accepted everywhere now, but some older marinas or remote fuel docks still prefer cash or run their own account system. If you're cruising remote areas — the Maine coast, coastal British Columbia, the Florida Panhandle outside the main harbors — keep some cash on the boat and ask about payment methods before you're committed to the dock.
This matters more than most sailors realize: high-traffic fuel docks have better fuel. Faster turnover means the diesel in the storage tanks is newer, has less time to degrade, and has less accumulated water at the bottom of the tank. A fuel dock at a busy marina in Annapolis or San Diego moves a lot of volume; the fuel you're putting aboard was probably delivered within the last week or two.
A seasonal marina in a remote location — open May through October, serving twenty boats a week — may have diesel in its storage tanks that's been sitting since the previous summer. Water accumulates. Algae blooms. The fuel is still combustible but it's not clean. If you're fueling at a low-traffic or obviously quiet facility, consider carrying a portable water-separating filter to run fuel through before it goes aboard, or at minimum watch your primary fuel filter on departure day. A dark, cloudy primary filter element after taking on fuel at a new dock is a warning sign.
Smell the diesel when it comes out of the hose. Fresh diesel has a clean, sharp smell. Old diesel with microbial contamination smells faintly sour or musty — similar to dirty engine room bilge water. If you notice that smell, say something to the attendant. It doesn't always mean contaminated fuel, but it's worth noting.
Most marinas are not near grocery stores. This is not an accident — the most attractive locations for marinas (protected harbor, deep water, accessible approach) are rarely in the middle of town. The result: if you need to provision from a marina, you're usually dealing with one of a few scenarios.
The dinghy trip is available at anchorage-adjacent marinas where a town dock or public float puts you close to a shopping district. It's genuinely useful in classic cruising destinations like Port Townsend, Beaufort NC, or Camden ME, where the provisioning distance from the water is walkable. Less useful when the "town" is a fuel depot and a bait shop.
The marina courtesy car is a genuine amenity at cruiser-focused facilities — often an old beater with 80,000 miles and a sign-out sheet. If your marina offers it, sign up early; it's usually first-come. At many marinas this is a genuine community resource and the only way to reach a grocery store without a thirty-dollar Uber.
Uber and Lyft exist in most coastal cities and work reasonably well for marina provisioning. The practical limit is how much you can carry back: four bags of groceries in an Uber is manageable; a week's provisions for two adults is a challenge. A rolling cart or a set of folding bags with handles makes a significant difference. In areas with weak rideshare coverage — rural Maine, parts of the Pacific Northwest — Lyft surge pricing on weekends can be substantial.
West Marine is ubiquitous near marinas, and within its lane it's genuinely useful: safety gear, fenders, lines, stainless hardware, basic electrical supplies, flares, life jackets, oil, filters. If you need a seacock ball valve or a set of docklines at 4 PM on a Saturday, West Marine is the answer.
What West Marine is not: a chandlery with deep inventory. Specialty items — custom blocks, specific Lewmar hardware, unusual zincs, a specific gauge of tinned marine wire — require calling ahead or ordering online. The inventory at any given West Marine location varies, and the staff knowledge varies even more. For critical hardware replacements, use the West Marine website to verify stock at a specific store before you drive there.
Fresh provisions, specialty food, and wine or spirits are not available at West Marine or any boating supply store. Plan accordingly: provision before you enter the marina, or plan a dedicated provisioning run on arrival day before you get comfortable.
When your boat is being hauled and you're going to be out of the water for a week or more, provision before the boat goes on the hard. You will not have easy access to the boat's galley (the companionway ladder is gone or inconvenient, the boat is on jackstands at face height, and cooking on a boat in a boatyard is generally discouraged). More importantly, once you're in the boatyard mode — sanding, painting, replacing fittings — you will not want to stop to make a grocery run every day.
Stock up on non-perishables before the haulout: things you'll want within reach for the project week (coffee, snacks, drinks) plus the provisions you'll want when the boat is launched and you're ready to leave the yard immediately. Nothing is more anticlimactic than a successful haulout and relaunch followed by an hour at the grocery store before you can go anywhere.
Marina water hoses are shared among many boats, and flow rate from a dock hose is typically 5 to 8 gallons per minute. That means a 100-gallon tank takes 12 to 20 minutes to fill — not the quick operation some sailors seem to expect. Be patient with the fill process, especially if other boats are waiting for the water hose.
Water quality at marinas is potable but varies. Municipal water in coastal areas is treated and generally fine, but shore-side water has been sitting in hoses that bake in the sun and may impart a plastic or chemical taste to your tanks. Filter before it goes aboard: a simple inline activated carbon filter on your fill hose removes most taste and odor issues and is cheap insurance. Change the filter cartridge at the start of each cruising season.
The hose protocol at busy marina docks is simple etiquette: connect, fill, and disconnect. Do not leave the hose running unattended and walk away. Do not leave your fill cap open and go below for twenty minutes. At crowded marinas in peak season, other boats are waiting, and dock masters notice the people who monopolize the water hose. Return the hose to its holder or coiled position when you're done.
If you're on an extended passage and want to carry maximum water, fill tanks as late as practical before departure — water tanks left full for weeks in warm climates can develop bacterial issues. A small amount of bleach (a teaspoon per 50 gallons) is the traditional treatment if you're concerned. Watermakers solve most of this problem but add their own maintenance complexity.
For choosing which marina to use in the first place, see How to Choose a Marina. For a regional overview of Pacific Coast facilities including fuel dock availability by area, see Pacific Coast Marinas.