Why Bad Boat Spark Plugs Can Cost You More Than You Think

Boat Maintenance Tips from the Pro Mechanics at Professional Marine

When it comes to routine boat maintenance, spark plugs are one of the most overlooked components, and one of the most important. A bad or low-quality spark plug can cause serious performance issues, increased emissions, and even long-term engine damage. Whether you're heading out on a Yamaha 242X, a MasterCraft X24, or a Sea-Doo GTR 230, your ignition system needs to be dialed in for a smooth, reliable ride.

At Professional Marine, we believe in doing things right the first time, and that includes ONLY using OEM parts for all our Boat and Jet Ski service work.  And that’s why we always say: Buy nice, or buy twice.

What Happens When You Run Bad Spark Plugs?

1. Engine Misfires & Rough Performance

Misfires caused by faulty spark plugs can result in rough idling, hesitation, sluggish throttle response, and reduced power. It's an issue we see across many engine types, from Mercury outboards, Yamaha Jet drives, to Rotax-powered Sea-Doo Jet Skis.

But it’s not just the spark plugs, a worn distributor cap is one of the most neglected parts in marine maintenance. It’s critical to ensure consistent spark delivery across all cylinders. Replacing your distributor cap during your annual tune-up (especially on MerCruiser and Volvo Penta inboards) is a smart, inexpensive upgrade that pays off in smooth performance and easier starts.

2. Incomplete Combustion & Reduced Fuel Efficiency

Worn spark plugs, and faulty caps cause incomplete combustion, leading to increased fuel consumption and poor mileage, a serious concern when powering larger boats like a Cobalt runabout or cruiser, Regal 28 Express, or the always popular SeaRay Sundancer.

3. Engine Knocking & Long-Term Wear

Unchecked misfires can lead to engine knocking and premature wear, especially on high-performance wake boats like a Nautique G23, Malibu Wakesetter, or Centurion Ri265, where engine demand is high, and reliability is crucial.

4. Hard Starts & Cold Weather Struggles

Especially common in fishing boats like a Lund Pro-V, Alumacraft Trophy, or Tracker Targa, bad spark plugs make cold starts even more difficult—often resulting in long cranks or no start at all.

5. Contaminated Engine Oil & Catastrophic Damage

Misfires can cause raw fuel to wash down cylinder walls, diluting oil and increasing internal wear. Over time, this can damage piston rings, valves, and even the catalytic converter—which are costly repairs on any Yamaha Jet Boat, Supra wakeboat, or Tige surf boat.

Why Cheap Spark Plugs Aren’t Worth the “Savings”

We see it all the time: a boat owner grabs the cheapest plugs off the shelf or uses automotive-grade parts that aren’t designed for marine engines. The result? Inconsistent spark, early failures, and breakdowns that could’ve been easily avoided.

Whether you're driving a Sea-Doo Switch, a Bennington pontoon, or an MB Tomcat surf boat, the difference between OEM vs. aftermarket parts matters—especially when you're already investing in maintenance.

Smart Tune-Ups, Done Right

If you're already swapping out your spark plugs during a spring tune-up, go the extra mile:

• Replace the distributor cap and rotor (if applicable).

• Use marine-rated, OEM-spec spark plugs.

• Have your ignition system inspected by a certified marine technician.

  
  

At Professional Marine, we tune and maintain a wide range of watercraft—from Yamaha VX, Bayliner Cruisers and Sea-Doo RXT 325s, to Malibu Boats, Supreme surf boats, Chaparral cruisers,  Ranger fishing boats and Bennington Pontoon boats. We know what works and what doesn’t—because we’ve seen what happens when shortcuts are taken.

Final Word: Don’t Let a $12 Spark Plug Wreck a $100K Boat

Routine maintenance isn't just about protecting your investment—it's about performance, reliability, and peace of mind. Whether you’re pushing across the lake on a Boston Whaler, towing riders on a Moomba surf boat, or navigating a tight marina in your Four Winns cruiser, you need your engine to perform.

Buy nice, or buy twice. Cheap parts are expensive mistakes waiting to happen.

About Professional Marine

At Professional Marine, we are dedicated to "redefining marine standards" by delivering top-tier service and exceeding customer expectations. As a full-service marine center, we provide expert boat repairs, maintenance, upholstery, detailing and storage solutions for all types of watercraft. With over a decade of experience, we take pride in offering high-quality workmanship, exceptional customer service, and lifelong relationships with our clients. Whether it’s summer preparation, routine maintenance, or major repairs, we are committed to keeping you on the water with confidence.