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United Marine
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Tune Up Kit Thunderbolt Small Block Tri-Pak | United Marine 1-103
Keep your Mercruiser small block running at peak performance with this essential three-piece tune up solution. The kit delivers everything needed for reliable ignition—a quality distributor cap, precision rotor, and dependable spark plug wires—all engineered specifically for Thunderbolt distributor systems. Regular maintenance with genuine components ensures smooth starts, consistent firing, and extended engine life on the water.
When it comes to marine performance, your ignition system is the heartbeat of your vessel. If you are experiencing sluggish starts, engine hesitation, or poor fuel economy in your MerCruiser, it is likely time for a comprehensive refresh. The United Marine 1-103 Tune Up Kit Thunderbolt Small Block Tri-Pak is specifically engineered to restore the power and reliability of your V8 engine.
Designed for MerCruiser 5.0L (305 cu in) and 5.7L (350 cu in) engines equipped with Thunderbolt IV or V ignition systems, this "tune-up in a box" provides high-performance components that often exceed OEM standards.
The "Tri-Pak" name refers to the three core pillars of your ignition system included in one convenient package. By replacing these components simultaneously, you ensure a consistent spark and optimal timing.
MEGA-MAG 8mm SSC Silicone Spark Plug Wires: These aren't your standard wires. They feature a 100% silicone jacket rated for up to 500°F, ensuring they won't crack or degrade in the high-heat environment of a marine engine bay. With 90-degree boots on both ends, they offer a clean, secure fit that resists vibration and moisture.
Heavy-Duty Distributor Cap: Featuring solid brass contacts, this cap provides superior conductivity and corrosion resistance compared to cheaper aluminum alternatives. It is built to withstand the harsh, salty conditions of marine use.
High-Performance Rotor: Engineered for precision, the rotor works in tandem with the cap to deliver a high-energy spark to each cylinder without arcing or misfiring.
Essential Accessories: The kit also includes an ignition coil wire, wire separators to prevent cross-firing, and dielectric silicone grease to protect connections from moisture and oxidation.
Maintaining a marine engine requires parts that can handle constant load and high humidity. The United Marine 1-103 kit is a favorite among professional marine mechanics for several reasons:
Maximum Spark Energy: The ultra-low resistance carbon-latex core in the Mega-Mag wires ensures that maximum voltage reaches your spark plugs, leading to more complete combustion and better throttle response.
EMI/RFI Suppression: Modern boats are packed with electronics. This kit is designed to suppress electromagnetic interference, preventing "tachometer bounce" and keeping your GPS and radio signals crystal clear.
Corrosion Protection: Marine environments are brutal on electrical components. The use of stainless steel and brass terminals ensures your ignition system remains rust-free and reliable season after season.
The United Marine 1-103 is a direct replacement for several Mercury/MerCruiser part numbers, including 84-816761Q4 and 84-816761T4. It is the ideal choice for small block V8 engines (305 and 350) from the early 1980s through the late 1990s that utilize the Thunderbolt ignition system.
Don't wait for a breakdown in the middle of the lake to think about your ignition system. A seasonal tune-up with the United Marine 1-103 Thunderbolt Small Block Tri-Pak is an investment in peace of mind. You’ll enjoy smoother idling, faster hole shots, and the confidence that your boat will start every time you turn the key.

Would have been 5 stars but, I did not receive a promotional sticker with my $2000 drive unit. Just kidding, everything was great!
Great company to work with!
Ordered a Piranha Propellers Complete A-Series 4 Blade Propeller from Macomb Marine Parts and even though we’re international, it arrived in just over a week — fast and reliable service. The propeller itself is a real lifesaver. We had the same model before, and after hitting a rock that damaged two blades, we were able to swap them right on the water and make it back to the marina without issue — something you simply can’t do with a regular aluminum prop. For peace of mind we decided to buy a complete new set (hub and blades) since an impact like that could cause hidden damage, but the system really proved its worth.
3 in. Exhaust Elbow | Pleasurecraft R029001
Excellent part.
I couldn’t find a Piranha propeller dealer near me in Canada but found Macomb Marine Parts who could deliver to me. The order process was smooth and I was even contacted via email for clarification regarding blade shape and they were very helpful in choosing the best shape for my purposes.
I can’t comment on the prop’s performance yet as we haven’t had the boat in the water yet.
Perfect replacement. thank you
Perfect replacement
Perfect match to the original Chris Craft blue. Competitive price and delivery was quick
Great Product, easy to install, work well
Obtaining magnesium anodes to install on the OMC Cobra (SX-C) sterndrive, for fresh water use. Received the anode within a week of ordering the part, which is not going to be installed until Spring.
Black Liquid Electrical Tape - 4 oz. | Star Brite 084104B
As described
Very Happy!! Just what I needed!!
Outdrive spent 4 months docked in salt water with no visible rust on the stainless steel braided hoses
Would have been 5 stars but, I did not receive a promotional sticker with my $2000 drive unit. Just kidding, everything was great!
Great company to work with!
Ordered a Piranha Propellers Complete A-Series 4 Blade Propeller from Macomb Marine Parts and even though we’re international, it arrived in just over a week — fast and reliable service. The propeller itself is a real lifesaver. We had the same model before, and after hitting a rock that damaged two blades, we were able to swap them right on the water and make it back to the marina without issue — something you simply can’t do with a regular aluminum prop. For peace of mind we decided to buy a complete new set (hub and blades) since an impact like that could cause hidden damage, but the system really proved its worth.
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