Quicksilver – Cylinder Bore Seal | Engine Sealing Components | Precision Fit Design | 8597721

Overview

Anyone who has spent enough time running a Mercury outboard knows how much trust you place in the internal seals. They’re hidden away, doing quiet work, yet they make the difference between an engine that pulls hard and one that feels tired. This Quicksilver cylinder bore seal has that dependable, reassuring feel — the kind of part you install once and forget about because it simply does its job every time you turn the key. When your powerhead is sealed the way Mercury intended, everything downstream just feels tighter and smoother.

Key Features

• Precision-fit cylinder bore seal for select Mercury and Mariner engines
• Designed for EFI and DFI outboards in the 135–200 horsepower range
• Fits select 175–240 horsepower JetDrive SportJet engines
• Built to Mercury Marine OEM engineering standards
• Easy to install using common tools
• Quicksilver part number 8597721

Engine & Boat Compatibility

• Mercury and Mariner 135–200 horsepower EFI and DFI outboards
• Select Mercury JetDrive 175–240 horsepower SportJets
• Common for performance fishing boats, jet boats, pontoons, and family runabouts
• Suitable for both freshwater and coastal setups

Performance & Practical Benefits

A proper bore seal creates a cleaner, tighter combustion environment, which translates into steadier throttle response and healthier engine behavior. You’ll notice the benefits most in the mid-range — that sweet spot where engines spend so much of their life. The seal’s structure helps maintain consistent compression, improving efficiency and long-term reliability.

In real-world use, the part stands up well to the heat and pressure changes that come with long days on the water. Installation is straightforward, and once it’s in place, it sits securely without fuss or re-torqueing. That steady, secure fit is what keeps your engine feeling strong from one season to the next.

Why Buy OEM

Internal engine components aren’t the place to experiment. With a genuine Mercury Marine part, you know you’re getting the exact fitment and material quality your engine was designed around. Aftermarket seals may look identical but often miss the small details — tolerance, compression resistance, longevity — that keep your engine performing at its best. Choosing OEM is about avoiding problems before they start and protecting the investment sitting on your transom.

FAQ

Q1: Which engines does this bore seal fit?

It fits select Mercury and Mariner 135–200 horsepower EFI and DFI outboards, plus certain JetDrive SportJet engines.

Q2: What sets it apart from aftermarket seals?

Its exact fit and Mercury-specific engineering ensure long-term reliability under real marine operating conditions.

Q3: How do I confirm it’s the right part?

Check your service manual or parts listing. If it calls for part number 8597721, this is the match.

Q4: Can it be used in saltwater and freshwater?

Yes. The material holds up well in both environments.

Q5: Is installation easy?

For most mechanically comfortable boat owners or technicians, installation is very straightforward.