Portable Gold Dredge for Sale: Sizes, Prices, Rules

Portable gold dredge for sale: what to expect to pay and where it is legal

A new portable suction dredge costs about US$2,700 for a 2-inch backpack unit and about US$8,650 for a 5-inch machine with a 9 hp Honda engine, going by the Keene Engineering master price list of 2 May 2025. Twin-engine 6-inch and 8-inch models run from about US$10,700 to US$35,000. The size you buy matters less than the size you may legally run: several western states cap the suction intake at 4 to 6 inches, and California bans suction dredging in rivers, streams and lakes altogether.

This guide is for people deciding which dredge to buy and where it can work: licence holders, small-scale operators and consultants advising them. It compares intake sizes with maker prices, shows how much gravel each size is claimed to move and how much one field test measured, and lists the permit limits in six states. A payback calculator near the end lets you test your own gravel grade. The 8-inch class is covered as a size, not a brand (see the questions at the end).

A suction dredge is a floating pump and hose. The hose sucks gravel and water from the stream bed, and a sluice box (a sloped trough with ridges called riffles) catches the heavy gold while the rest drops back into the stream. A “portable” dredge is one that breaks down into parts a person can carry to the water, so it is mostly the 2-inch to 6-inch classes that people mean.

How we chose the numbers on this page

Prices come from one maker’s published list because it is dated and complete: Keene Engineering, 2 May 2025, with the maker’s own warning that prices can change without notice. Proline Mining Equipment also publishes a price form, but it is undated and the company says its prices change often, so we quote it only as an older reference point. We did not use reseller or auction listings.

Capacity figures are maker claims or test results and are labelled as such. Permit limits come from the state agency or the rule text, opened in October 2026. Where a state’s current permit text could not be confirmed, the table says so. Nothing here is a ranking of brands: we have not tested any dredge, and the list prices show size classes, not quality.

Dredge sizes compared: price, power and best use

Dredge size is the inside diameter of the suction intake. Bigger intakes move more gravel per hour, but they need a bigger pump and engine, weigh more and are harder to carry. Keene’s own guidance on balanced dredge set-ups pairs each size with an engine, a pump rated in gallons per minute (GPM) and a sluice box width. The table puts those pairings next to the 2025 list prices.

Chart

Keene list price by dredge intake size

US$, one model per size, list price of 2 May 2025

Prices are the model as listed by Keene on 2 May 2025; check what is included (compressor, floats, hoses) before comparing quotes. The same list prices a 5-inch pontoon float assembly at US$2,250 on its own, so ask whether floats are in the quoted dredge price. For comparison, an older Proline order form priced a 5-inch twin-engine dredge with two Honda GX200 engines at US$7,340 and a 6-inch twin GX270 model at US$9,990, but the page is undated and warns that prices change.

How much gravel does a portable dredge move per hour

Maker brochures give a ceiling, not an average. Proline states “up to 16 cubic yards per hour” for its 5-inch dredge, with a 20 by 60 inch sluice box, a 5-inch by 20 foot hose and a weight of 300 lb for the single-engine model (Proline 5-inch page, undated). Oregon’s environmental agency tabulated the maximum figures from both makers in its 700-PM permit fact sheet, and the gap between the two makers is large at 3 and 4 inches, as the chart shows.

Chart

Maker maximum output by dredge size

Cubic yards of gravel per hour, as tabulated by Oregon DEQ

A field test gives a more cautious picture. Keene’s 5-inch jet-flare test in the East Fork of the San Gabriel River, California, moved about 241 cubic yards over 20 work days (the report says part of this was oversize rock moved by hand or winch, and the ground was clay-bound), which is 2.41 cubic yards per engine-run hour or 3.01 per hour of actual dredging when the report assumes 4 of every 5 run hours were spent dredging. That is about a fifth of the Proline ceiling, and the report found no identifiable gold loss to the tailings (Keene 5109H test report, undated, by a named author on the maker’s site). It is one stream, one machine and one crew. Use it as a reminder that depth, cobbles, current and rest breaks cut the hourly rate far below the headline number. Oregon’s fact sheet notes the same: less material moves in rocky ground than in gravel.

What to check before you buy: pump, jet, sluice and hose

Keene’s technical notes make several points that apply to any brand. Check these in the spec sheet, not only the sticker price.

• Pump pressure and volume must balance. A cheap high-volume, low-pressure trash pump gives weak suction; Keene calls the pump the place where “you get what you pay for”.
• Sluice width must match the pump. A 10-inch box behind a 3-inch dredge makes water run too fast to hold gold, according to the same notes.
• Jet or suction nozzle. With a suction nozzle the water enters the hose on the suction side, so friction builds quickly: Keene’s longest recommended suction hose is about 20 feet. A power-jet system can pull gravel over 100 feet with a larger motor and pump. Ask which one the quote is for: Keene lists the 2.5-inch model at US$3,895 with a suction nozzle and US$4,350 with a power jet.
• Keep the box at water level. A sluice raised even a few inches above the water cuts suction.
• Riffles and slope. The US EPA says sluices are usually inclined 5 to 15 degrees and that riffles or a drop between sluice sections break the flow and raise recovery; sluices produce a low-grade concentrate that still needs panning (EPA, small-scale gold mining without mercury).
• Air supply for diving. A compressor is an add-on on most models. On Keene’s 2025 list, adding a compressor to a 4-inch Ultra dredge raises the price from US$4,850 to US$5,795.

New or used?

Ask for a short run test on the pump and engine, check the impeller and pump housing for wear (Keene lists some replacement impellers from US$185 to US$449), and confirm the sluice and floats are the ones that go with that engine. Check also that the size still fits the rule where you plan to work: a 6-inch machine is useless on a river that caps motorized intakes at 4 inches.

Where suction dredging is legal in the western states

Dredge rules sit with the state water-quality agency, the state fish agency and the land manager, and they differ sharply. The table below covers six states reviewed in October 2026. Other states, including Nevada, Arizona and Colorado, have their own rules that were not reviewed here. Always confirm with the agency before you buy.

Chart

Largest suction intake each state’s rules allow

Inches; motorized suction dredges; Idaho omitted because its 2024 permit limits were not confirmed

For Washington, the details are long enough for a page of their own: see our guide to Washington dredge rules and permits. In short, the state’s Ecology page says that since 11 June 2020 motorized and gravity-siphon mining is prohibited in critical habitat waters and in fresh waters designated for salmon spawning, rearing and migration, and that an individual permit is needed elsewhere. The rule text also requires motorized rigs to stay at least 200 feet apart and intake screens with openings no larger than 5/64 inch.

California is not only a legal question but an enforcement one: the fish agency has issued news releases about citing people in Siskiyou County for illegal suction dredging (CDFW news). Oregon’s list also leaves out State Scenic Waterways and waters on or bordering tribal land, according to the fact sheet. In Montana, a local conservation district permit and, on three named rivers, a Corps of Engineers permit may also be needed (Montana DEQ reminder sheet).

Do you need a claim, and what about federal land

You do not need a mining claim to suction dredge on public land, but you do need to ask the local land manager what paperwork applies. A Bureau of Land Management Q&A (BLM mining claims packet, February 2026) says exactly this, and adds that a claim only gives the exclusive right to the minerals being claimed. It also says that you may need permission from the claimant if you prospect on someone else’s claim. So the order is: check the stream’s permit rules, check who owns or manages the ground, then buy the machine.

Infographic

Buying a dredge in 5 steps

1. 1Find the stream ruleCheck the intake cap and permit for the exact water.
2. 2Check the landAsk the land manager or claim owner what applies.
3. 3Sample the gravelPan or hand-sluice before spending on a machine.
4. 4Pick the sizeMatch intake, pump and box width to the cap.
5. 5Ask what is includedFloats, compressor, hoses and spares can be extra.

Our video on claims and land ownership explains why a claim is not the same as owning the land.

▶ Explains why owning a gold claim is not owning the land, and what to check before buying one. · 3:19

Safety, mercury and the environment

Dredging has risks that a price list does not show: cold water, engine fuel on a floating platform, hose entanglement and, for divers, air supply from a compressor. Work with a partner, wear a flotation device and keep fuel away from the water. Washington’s rule text requires fuel to be stored outside the stream’s scour zone and any sheen reported.

Do not use mercury to catch fine gold. The EPA’s guidance says that gravity methods such as sluices can eliminate or greatly cut mercury use. Gold you recover from a sluice is a concentrate, and it is sold or refined in a separate step by a licensed buyer or refiner. A short clay-animation video from us shows what refining involves.

▶ Follows gold from rock to ring: mining, crushing, processing and refining. · 5:27

Check the ground before you spend on a dredge

A dredge only pays if the gravel carries gold, and the cheapest test is a pan or hand sluice sample before anything else. The calculator below shows why. If you hold a claim or licence and want to see which parts of it look worth sampling, satellite mineral detection maps rock alteration and structure on your boundary from space; it does not detect placer gold in a stream bed. For US gold supply and rural context, see our comparison of US gold reserves, and for a different dredge topic, gold dredge technology and gold dredge design. For Canadian placer claims, our Yukon placer guide covers claim records. If you run a business or licence that needs larger-scale mapping, you can request a quote.

Does a dredge pay back? A worked example

Take the Keene 5-inch at US$8,650, the measured 3 cubic yards per dredging hour, 100 hours a season, a gravel grade of 0.1 gram of gold per cubic yard (an example, not a benchmark), 80 percent recovery, a gold price of US$4,000 per troy ounce (an example; use today’s price) and US$20 an hour for fuel and wear. That gives about 0.77 troy ounce, or roughly US$3,100 gross and about US$1,100 after running costs, so it takes several seasons to repay the machine. At a richer grade the answer changes quickly, which is why sampling comes first. Change the inputs in the calculator.

Frequently asked questions

How much does a portable gold dredge cost?

On Keene Engineering’s 2 May 2025 list, a 2-inch backpack jet-flare dredge is US$2,695, a 3-inch Ultra with a Honda GX120 is US$4,295 and a 5-inch with a GX270 is US$8,650. Larger twin-engine models cost US$10,700 to US$35,000. Prices change, and accessories such as floats and compressors may be extra.

What size gold dredge should a beginner buy?

Start from the rule where you will dredge. If your river caps intakes at 4 inches, as Oregon and Montana do, a 3-inch or 4-inch unit is the most you can use. A 2.5-inch or 3-inch dredge keeps the engine small (4 to 5.5 hp in Keene’s balanced set-ups) and the cost low (US$3,895 and US$4,295 on the 2025 list). This is a judgement from the size classes above, not a tested recommendation.

Is it legal to use a gold dredge in California?

No. The California Department of Fish and Wildlife says suction dredging is currently unlawful in the state’s rivers, streams and lakes and that it cannot issue permits under existing law.

Do I need a permit to use a gold dredge in Washington?

Yes. A written Hydraulic Project Approval from the fish and wildlife department is required, along with a water-quality permit from Ecology, and motorized mining is banned in salmon habitat. See our Washington guide for the steps.

What is the biggest dredge allowed in Alaska?

Alaska’s DEC general permit AKG375000 covers suction dredges with an intake of 6 inches or less and an engine of 18 hp or less in fresh water (23 hp in marine water). The permit runs to 31 December 2027, and registrations, where required, expire each 31 December. Other state or federal approvals can still apply.

How many cubic yards per hour does a gold dredge process?

Oregon’s fact sheet lists maker maximums of 2 to 20 cubic yards an hour from 2-inch to 6-inch for Proline, and 1.4 to 17 for Keene. Keene’s field test of a 5-inch machine measured 3.01 cubic yards per dredging hour. Expect your own figure to fall well below the maker’s maximum.

What is an 8-inch dredge, and what happened to “Dredge 8”?

We found no maker or model named “Dredge 8”. An 8-inch dredge is a size class: Keene lists an 8-inch twin-engine dredge at US$29,995 and a 40 hp version at US$29,950. At that size the machine is for commercial placer work and is above the 6-inch limit of Alaska’s general permit.

Can I use a gold dredge on a mining claim?

Owning a claim does not remove the state water-quality rules, and you do not need a claim to dredge on public land (BLM Montana and the Dakotas Q&A). In both cases you must follow the stream’s permit and the land manager’s rules.

Do I need mercury to recover gold from a dredge?

No. A sluice with riffles and a pan for the concentrate recovers gold by weight alone, and the EPA says gravity methods can eliminate or greatly cut mercury use.

How much does it cost to run a gold dredge?

There is no current sourced hourly cost for fuel and wear (Keene’s undated test burned 0.42 gallon of gasoline per run hour at a fuel price far below today’s), so the calculator lets you enter your own. Keene’s field test ran a 9 hp engine at about 60 percent throttle for most of the test, which affects fuel use. Replacement pump parts add to the cost: some impellers on Keene’s list start at US$185.

Where can I find gold-bearing gravel to dredge?

Start with public records of known placer districts, your local geological survey and the land manager’s rules, then confirm with pan samples. Satellite mapping can help you screen a large claim for target areas, but it cannot see gold in a stream bed.