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Hynautic KS-18 Seal Kit for K8 Cylinders & HC5806

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SKU:
KS-18
Condition:
New
  • Hynautic KS-18 Seal Kit for K8 Cylinders & HC5806
  • Hynautic KS-18 Seal Kit for K8 Cylinders & HC5806
$95.00
In Stock - Ships Same Day M-F (Order by 5pm EST)

Description

Hynautic KS-18 - Seal Kit for K-8 Cylinders and HC5806 Applications

KS-18 is a genuine Hynautic cylinder seal kit used to reseal K-8 steering cylinders and related HC5806 applications. Use this kit when servicing a cylinder with seepage at the rod gland, moisture intrusion, or suspected internal bypass due to worn seals - provided the rod and bore are in good condition.

Compatibility

  • Fits: Hynautic K-8 cylinders and HC5806 applications
  • Alternate K-8 kit: For K-8 cylinders prior to 4-15-94, see KS-09
  • How to confirm: Check cylinder stamping, tags, or service history. If you are unsure, contact Tech Support with clear photos of the end cap, rod end, and any labels.
  • Qty needed: One (1) kit reseals one (1) cylinder

What’s Included

  • Seal and O-ring set for one compatible cylinder application
  • Rod wiper(s) and backup rings as applicable
  • Additional O-rings for glands/ports as applicable

Note: Contents can vary slightly by cylinder revision. Reuse of hard parts is expected unless damaged.

Installation Tips

  • Protect the rod: Avoid clamps, pliers, and sharp tools on the polished rod surface. Any nick can cause immediate leakage.
  • Inspect before reseal: If the rod is pitted or the bore is scored, seals may fail quickly - rebuilding is recommended.
  • Keep it clean: Clean the exterior and gland area before disassembly to prevent debris from cutting new seals.
  • Lubricate seals: Use a light film of compatible steering/hydraulic fluid during assembly - do not install seals dry.
  • Bleed after service: Any air introduced must be fully bled to restore consistent steering feel.

Maintenance Guidelines

  • Inspect the rod and gland area periodically for fluid film, salt buildup, and corrosion.
  • Keep bilges as dry as practical and rinse salt deposits around the cylinder when accessible.
  • If steering feel changes (drift, pull, or frequent correction), verify fluid level and bleed the system before condemning components.

FAQs

How is KS-18 different from KS-09?
KS-18 is used for K-8 cylinders and HC5806 applications (this page). KS-09 is used for K-8 cylinders prior to 4-15-94. If you are unsure which version you have, send photos to our Tech Support Page.

Will KS-18 fix internal bypass?
Sometimes. If bypass is caused by worn internal seals and the rod/bore are in good condition, resealing can restore performance. If the bore is scored or corrosion is present, a rebuild is typically the better long-term fix.

Do I need one kit per cylinder?
Yes - one KS-18 kit is intended to reseal one cylinder.

Should I rebuild instead of reseal?
If the rod is pitted, the bore is scored, or the cylinder has chronic leakage, rebuilding is often the most reliable path.

Related Hynautic Cylinder Seal Kits

Part No. Fits Cylinder(s) Notes
KS-18 K-8 and HC5806 applications This page
KS-09 K-8 (prior to 4-15-94) Older K-8 variant
KS-15 K-5(B) Legacy cylinder kit
KS-08 K-7 Legacy cylinder kit
KS-07 K-10 Legacy cylinder kit
KS-19 K-6 Limited availability
KS-13 K-3 (prior to 4-15-94) Older K-3 variant
KS-17 K-3, K-4, PSK11-12 Alternate K-3/K-4 kit depending on revision
KS-11 K-1 Single-cylinder kit
KS-12 K-2(B) K-2 variant
KS-02 K-18, K-19, K-20 Ball bracket style
KS-14 K-51 Large inboard cylinder kit

Downloads and Resources

Description Link
Hynautic Steering System Manual - general reference LINK [PDF]
Hydraulic Cylinder Installation and Reference Guide LINK [PDF]
Hynautic Cylinder Rebuild Service LINK [Service]

Questions?

  • No Sales Tax on purchases outside California
  • Buy Now Pay Later with Affirm or PayPal
  • FREE Ground Shipping to the Lower 48 States
  • Seatech Marine Products, Inc. is an authorized dealer, service center and installer for Hynautic.

International, USVI, Puerto Rican, Hawaiian and Alaskan Customers: We ship worldwide and via USPS. If shipping looks high, contact us for a quote.

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Warranty Information

Seatech Marine Products is an authorized dealer for Dometic that distributes SeaStar Products, this part has a 2 Year Limited Warranty from them. Please visit their website for full details: https://www.dometic.com/en-us/outdoor/support/warranty-statements
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