Tender davit and crane systems: hydraulic vs electric

Tender launching on cruising motoryachts uses either a davit (single arm, pivots overboard) or a full crane (rotating jib, greater reach). Two power classes: (1) ELECTRIC (Nautical Structures NS series, Marquipt, Steelhead Marine ES): 12V or 24V winch motor driving a wire rope, capacity 500-2500 lb. Ideal for tenders under 15 ft. Duty cycle limited, most electric davits are rated 5 minutes on per 30 min. Common failure: wire rope fraying (inspect every launch, replace at first broken strand), brake worn out (won't hold the tender still under load, dangerous), limit switch failed (over-travel damages the boom). (2) HYDRAULIC (Nautical Structures crane, Steelhead Marine hydraulic, Marquipt): boat's HPU or dedicated pump drives the boom. Capacity 1500-8000 lb for tenders 15-25 ft plus jet skis and water toys. Smoother lift, safer, higher duty cycle. Costs 3-5x an electric equivalent installed. Maintenance rules: (a) Grease pivots monthly with marine grease (not automotive, marine grease has zinc oxide corrosion inhibitor). (b) Inspect wire rope or synthetic line at every launch. Wire = broken strand rule; synthetic (Dyneema) = check for chafe and UV damage annually, replace every 5 years regardless. (c) Test the emergency lowering function annually, a hydraulic crane with a failed valve strands the tender high and dry. (d) Rated capacity plate should be visible from the operator position, never lift a tender that puts it near or over spec. (e) Winter storage: extend the boom fully, secure, coat exposed cylinders with anti-corrosion film.