Attwood SL35-50-5 Gas Spring Lift Support 50 lb

The Attwood SL35-50-5 is a gas spring, sometimes called a lift support or gas strut, rated at 50 pounds of output force. Its whole job is simple. Hold something up so you don't have to. On a boat that usually means a hatch, a livewell lid, a seat base, or an engine box cover that's supposed to stay open on its own while your hands are busy. When the spring in one of those gives out, the lid drops on your fingers or won't stay put in a chop. This is the part that fixes that.

Here are the numbers that matter. Compressed, it measures 8.46 inches end to end. Fully extended, it reaches 12.04 inches. That works out to 3.58 inches of travel, which is the stroke you get between closed and open. The output force is 50 pounds, meaning the spring pushes with 50 pounds of effort as it extends. The rod is 8 millimeters and the cylinder is 18 millimeters, so it's a compact strut that fits tight compartments. Both ends use eyelet mounts sized for a 10 millimeter ball socket, the common end fitting you'll find on most marine gas springs.

Where does a spring like this live on a boat? All over, honestly. Under-seat storage on a center console. The lid over a livewell or a bait station. Anchor lockers up on the bow. Engine hatches on smaller outboards and I/O boxes. Rod locker lids. Step-up storage on a pontoon. Anywhere a builder wanted a lid to open easily and stay open, there's a gas spring doing the work. Attwood has been building marine hardware for over a hundred years, and gas springs like the SL35 series are a staple of that catalog.

Matching force is the part people get wrong. A 50 pound spring is meant to balance a lid of a certain weight and hinge geometry. Too little force and the lid won't stay up. Too much and it flies open or strains the hinge. The safest way to get it right is to match what came off. Measure the compressed and extended lengths of your old strut, check the force rating stamped on the cylinder if it's still legible, and match all three. This SL35-50-5 gives you 8.46 inches compressed, 12.04 extended, and 50 pounds. If your original matches those numbers, you're set.

A quick word on mounting. Gas springs work best mounted rod-down, meaning the thin rod points toward the ground when the lid is closed. That keeps the internal seal bathed in oil and makes the action smooth and consistent. If your compartment forces a different angle, the spring will still work, it just tends to last longer rod-down. The eyelet ends slip over 10 millimeter ball studs and clip on, so swapping one is genuinely a few-minute job with no special tools.

Most boaters replace these in pairs. If a lid uses two springs and one has failed, the other is usually not far behind, and a mismatched pair makes a lid open crooked. It's sold here as a single gas spring, so order the count your setup needs. If you're not sure how many your lid uses, pop it open and look at the hinge points before you buy.

How do you know one is worn out? A tired gas spring gets slow, won't hold the lid at full height, or drifts closed on its own. Some start weeping oil around the rod. Cold weather makes a marginal spring worse, so a strut that barely held in summer will give up first on a cold morning. None of that is a repair. Gas springs are sealed and aren't serviceable, so when one quits you swap it. At this price, that's an easy call.

So who's this for? Any boater staring at a hatch that won't stay open, or a rigger who needs a known 50 pound strut with eyelet ends for a repower or a refit. It's a straightforward, no-drama replacement part. Match the length and the force, clip it on, and get back to the water.