Mercury Quicksilver Flo-Torq II Hub Kit 835257K1 | Mercury & Mariner Outboards

Mercury Quicksilver Flo-Torq II Hub Kit 835257K1

• Part Number: 835257K1
• Brand: Mercury Marine / Quicksilver
• Official Product Type: Flo-Torq II Propeller Hub Kit
• System: Propeller hub / outboard propeller drive
• HS Code: 848790
• Supersedes / Replaced By: No confirmed supersession — 835257K1 is current
• Related Kit: See also 835257K6 for alternate application fitment

What This Kit Does

The Mercury Quicksilver 835257K1 is a genuine OEM Flo-Torq II propeller hub kit for select Mercury and Mariner outboard engines. The Flo-Torq II system uses a resilient slip-clutch design that absorbs shock loads when the propeller strikes a submerged object. On impact, the hub allows the propeller to slip momentarily, protecting the gearcase, driveshaft, and lower unit from serious damage. After the event, the hub re-engages and normal propulsion resumes — provided the hub components have not been damaged beyond their limits.

The kit provides all components needed to install a compatible propeller on the outboard shaft, including the hub insert and required hardware for a complete, factory-specification installation.

Compatible Applications

• Select Mercury outboard engines — confirm by engine model and serial number
• Select Mariner outboard engines — confirm by engine model and serial number

Fitment depends on propeller bore size, shaft spline count, and engine model. Verify using the Mercury propeller and hub application chart for your specific outboard serial number before ordering. Flo-Torq II hub kits are not universal — the insert must match both the propeller bore and the engine spline specification.

If your application requires 835257K6, see the Mercury Quicksilver Flo-Torq II Hub Kit 835257K6 listing.

Kit Contents

Kit includes the hub body, resilient drive insert, and all required installation hardware for a complete Flo-Torq II hub assembly. Confirm the kit contents against the Mercury propeller installation diagram for your engine before beginning installation.

When to Replace This Kit

• Propeller removal for inspection, re-pitch, or replacement with a new propeller
• Hub insert is split, deformed, or has lost its resilience after a strike event
• Propeller slips under power load even when no recent strike has occurred
• Hardware (nut, washer, cotter pin) is worn, corroded, or removed during service
• Full propeller hub service at major outboard service intervals

Installation Notes

• Confirm the insert matches the propeller bore diameter and engine shaft spline count before installation
• Inspect the driveshaft splines and propeller bore for wear or corrosion before reassembly
• Install the hub assembly in the sequence shown in the Mercury propeller installation guide for your engine
• Torque the propeller nut to the specification in the Mercury service manual — do not estimate
• Install a new cotter pin through the castellated nut and shaft hole — never reuse an old cotter pin
• After a strike event, inspect the gearcase, driveshaft, and propeller for secondary damage before returning to service

Technical FAQ

What is the difference between 835257K1 and 835257K6?
Both are Flo-Torq II hub kits for Mercury and Mariner outboards, but they are designed for different propeller and engine spline configurations. The K-suffix designates the specific insert and hardware combination. Confirm which kit number appears in your engine’s propeller installation diagram by serial number — they are not interchangeable across applications.

Will the Flo-Torq II hub prevent all damage on a strike?
The Flo-Torq II system significantly reduces the risk of gearcase and driveshaft damage on propeller strikes by allowing the propeller to slip momentarily on impact. It does not eliminate all risk — very high-energy strikes can still damage the propeller, hub, and driveshaft. After any significant strike, inspect all propulsion components before returning to operation.

How do I know if the hub insert needs replacing?
After a strike, inspect the rubber drive insert for splitting, cracking, or visible deformation. A hub that allows the propeller to slip under normal power load — with no recent strike — also indicates a worn or damaged insert that should be replaced.

Can I reuse the propeller nut and cotter pin?
The propeller nut can typically be reused if it is in good condition and threads are undamaged. The cotter pin must always be replaced — it is a single-use fastener and must not be reused after removal.

Related Parts

• Mercury Quicksilver Flo-Torq II Hub Kit 835257K6
• Mercury Quicksilver Flo-Torq II Hub Kit 835274Q1
• Mercury MerCruiser Flo-Torq SSR Hub 8M0101602
• Mercury MerCruiser Flo-Torq SSR HD Hub 8M0101601
• Mercury MerCruiser Drive Sleeve 835290Q1
• Mercury Propeller Nut Kit 8M0056235
• Mercury Revolution 4 Stainless Propeller 14.6 x 17 RH 8M0151317
• Mercury Spitfire 8M0084497 – 4-Blade Aluminum Propeller 14 x 23 RH

Parts Desk Insights

The most common issue with Flo-Torq II hub kit orders is selecting the wrong K-suffix for the propeller and engine combination. The kit number must match the propeller bore and shaft spline count — 835257K1 and 835257K6 are not interchangeable, even though both are Flo-Torq II kits. Always confirm the correct kit number from the Mercury propeller application chart using the outboard serial number before ordering. The second most common issue is customers replacing only the propeller after a strike without inspecting the hub insert — a damaged insert will cause the new propeller to slip under load, and the problem will appear to be a faulty propeller when the real cause is the worn hub.