Sunstream Boat Lifts: Floating Hydraulic Lifts Explained
Quick answer
Sunstream is generally known for floating boat lifts that mount to floating docks and use hydraulics to raise the boat, so the lift moves with the water level. It suits owners with floating docks, variable water levels, or depths where pilings are impractical; confirm current models, capacities, and dock requirements with an authorized dealer.
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Sunstream is a brand associated with floating hydraulic boat lifts: lifts that attach to a floating dock and use hydraulic power to raise and lower the boat. Because the lift is part of the floating system, it rises and falls with the water, which removes most of the depth planning that piling-mounted and free-standing lifts require. This profile explains the general approach, who it suits, and how to evaluate one.
Independence note: Boat Lift Lab is independent and not affiliated with Sunstream or its dealers. Descriptions are general. Product lines, capacities, and warranty terms change, so verify current details with the manufacturer or an authorized dealer.
- Generally known for: floating hydraulic boat lifts that attach to floating docks
- Typical setting: floating docks on lakes, reservoirs, rivers, and coastal water
- Key advantage: follows the water level; no pilings needed for the lift itself
- Key requirement: a floating dock with the strength and flotation to support it
How a floating hydraulic lift differs from an air-chamber lift
Both styles float with the dock, but they create lift differently. An air-chamber lift, such as the type associated with HydroHoist, raises the boat by adding buoyancy. A floating hydraulic lift uses hydraulic cylinders to move a cradle relative to a floating base, with the base's flotation carrying the load. In practical terms:
| Factor | Floating hydraulic | Floating air-chamber |
|---|---|---|
| Lifting force | Hydraulic cylinders | Buoyancy from air in tanks |
| Main wear items | Seals, hoses, pump, fluid | Tanks, air lines, valves, blower |
| Typical failure symptom | Drifting down, slow lift, leaks | Boat settles as air leaks |
| Fluid considerations | Hydraulic fluid near water; ask about fluid type and leak control | No hydraulic fluid |
| Power | Electric pump, often with battery and remote options | Electric blower |
Both approaches have devoted owners. The better choice depends on your dock, your water, and local service. See floating boat lifts and hydraulic vs cable lifts.
The dock is half the system
A floating lift transfers the boat's weight into flotation and its attachment loads into the dock. If the dock lacks flotation or stiffness where the lift attaches, the dock can list, flex, or wear at the connections. Before buying any floating lift, ask the dealer to evaluate your dock specifically: freeboard, flotation condition, frame material, and anchoring.
Worked example: checking the load you are adding
A 20 ft center console: dry hull 2,400 lb, 150 hp outboard about 450 lb (check your engine), 50 gal fuel x 6.1 = 305 lb, two batteries at 65 lb = 130 lb, gear 400 lb. Loaded weight: 2,400 + 450 + 305 + 130 + 400 = 3,685 lb. With a 20% margin, the lift should be rated about 4,420 lb or more.
When the boat is lifted, the floating system carries that 3,685 lb plus the lift's own weight. If the lift weighs an assumed 1,000 lb, the flotation must support about 4,685 lb while keeping adequate freeboard. That is roughly 75 cubic feet of displaced fresh water (4,685 / 62.4). Your dealer should confirm the actual flotation design; these numbers show why dock condition matters.
Who a floating hydraulic lift tends to suit
- Owners with floating docks on reservoirs, rivers, or lakes with large level changes.
- Sites with deep water, rock, or very soft bottoms where pilings or free-standing legs are difficult.
- Owners who prefer not to replace cables, accepting hydraulic maintenance instead.
- Less suited to fixed docks on stable lakes where a simple free-standing lift would do, or to very exposed sites unless the dock system is designed for the conditions.
Maintenance and common problems
Hydraulic systems are reliable when kept clean and dry, but small problems grow if ignored. Typical owner checks:
- Inspect hoses and fittings for weeping, cracking, or abrasion each season.
- Check fluid level and condition per the manual; milky fluid suggests water contamination.
- Watch for the boat drifting down while raised, which can indicate internal seal or valve leakage.
- Keep the pump and electrical enclosure dry and the battery charged, if battery powered.
- Clean marine growth from flotation and moving parts.
For diagnosis, see hydraulic lift problems and hydraulic lift maintenance.
Buying used and finding parts
Floating hydraulic lifts are often sold with docks or moved between slips. On a used unit, record the data plate, run the lift through a full cycle, watch for drift over several hours, inspect hoses and cylinders for leaks and pitting, and check that flotation is sound. Ask a dealer whether parts such as seals, hoses, pumps, and remotes are available for that model and age. See finding boat lift parts and used boat lifts.
Questions to ask a dealer
- Will my existing floating dock support this lift, and what changes might it need?
- What is the rated capacity, and how does boat position affect it?
- What power options are offered (shore power, battery, solar charging)?
- What hydraulic fluid is used, and how are leaks contained?
- What minimum depth does the lift need when lowered?
- Which parts are stocked locally, and what does the written warranty cover?
Safety: Never stand or work under a raised boat; hydraulic lifts can drift down if a seal or valve fails. Shore power to any dock lift should be installed by a licensed electrician with GFCI or ELCI protection where required. Never swim near energized docks because of electric shock drowning risk.
Frequently asked questions
Can a Sunstream lift be added to any floating dock?
Not automatically. A floating lift adds significant weight and attachment loads, so the dock needs enough flotation, frame strength, and anchoring. Many floating docks can be adapted, but a dealer should evaluate your dock's condition and design before installation. Plan for possible added flotation or reinforcement.
Why does my floating hydraulic lift drift down?
Slow drift while raised usually points to internal leakage in a cylinder seal or a check valve, or to an external leak at a hose or fitting. Look for fluid on the lift and in the water first. If none is visible, internal leakage is likely and the lift should be serviced. Never work under the boat while diagnosing.
Is hydraulic fluid a problem near the water?
Any fluid leak into the water is undesirable and may raise environmental concerns. Ask the manufacturer or dealer what fluid the lift uses and whether a biodegradable option is available or recommended. Inspect hoses and fittings regularly and repair leaks promptly.
Do floating hydraulic lifts work in saltwater?
Floating hydraulic lifts are used in coastal water, but salt speeds up corrosion of metal parts and increases marine growth. Ask the dealer whether the specific model and its hardware are intended for salt water, and plan for more frequent rinsing and inspection.
Sources and further reading
- Manufacturer owner's manuals for floating and hydraulic boat lifts (general guidance)
- NFPA 70, National Electrical Code, Article 555, nfpa.org
- ABYC standards, including E-11 AC and DC Electrical Systems on Boats, abycinc.org
- U.S. Army Corps of Engineers Regulatory Program, usace.army.mil
- U.S. Coast Guard boating safety resources, uscgboating.org