RYDLYME Marine Biodegradable Descaler - 1 Gallon

Descaler for certain. Great Descaler for my 20 hp engine. Followed the instructions on dilution, let it run overnight. Cleaned engine inside and now works properly. No more limp mode or overheating. Cheap fix rather than taking it to the shop.

Great product works well

works well for my DF175 outboard engine.

Did the job but wish it wasnt so expensive. I need to flush my motor again as this worked at about 85% clean

Excellent solution and 100% recommended

This stuff worked so well! My 50hp Honda outboard was having cooling issues and I thought it was going to have to be rebuilt which would have cost a fortune. I set up a 5 gallon bucket with a 800gpm pond pump, removed lower unit and pushed a 1/2" hose from pump onto the cooling water tube sticking out bottom of engine. Also used a 3/16" barbed fitting to extend the tell tale hose to bucket. Removed thermostat. Then taped a trash bag with the bottom cut off onto the engine and draped into bucket. Mixed Rydlyme 50/50 with water, and ran the pump for 3 hours. The water almost turned gray there was so much salt and junk in it! When I dumped the bucket there was a thick sediment in the bottom too. Flushed the engine really well with fresh water right away. We just took the boat out and it's like a new outboard! So happy!!

2008 yamaha did the rydlyme flush runs much cooler and water jackets are clean

These RYDLYME Marine Biodegradable Descaler (typically sold in 1-gallon or larger bottles) is hands-down one of the most effective and safest tools for keeping your boat's cooling system, heat exchangers, outboards, inboards, and other water-cooled components running cool and efficient! This stuff is a game-changer for dissolving stubborn scale, calcium buildup, rust, barnacles, mussels, sand, and mineral deposits that clog passages and cause overheating—without the harsh risks of traditional acids like muriatic. It's fully biodegradable, non-toxic, non-corrosive to most metals (when used as directed—note: remove zinc/magnesium anodes first to avoid pitting), and safe enough that you can handle it with bare hands. No nasty fumes or gloves required for basic use, and it's eco-friendly for marine environments. Application is straightforward: dilute per instructions (often 1:1 or as needed), circulate through the system (muffs for outboards, pump setup for inboards/AC), let it work (foaming/bubbling shows it's actively dissolving gunk), flush thoroughly, and you're done. Users report dramatic results—overheat issues vanish, "pee" streams flow strong again, cooling passages look factory-fresh, and engines run noticeably cooler. One flush pulled out cups of solid debris from heavily fouled systems, restoring performance like new. Many boaters make it an annual or bi-annual ritual, saying it's worth every penny compared to downtime, repairs, or less effective alternatives like vinegar or Salt-Away for heavy scale. The concentrated formula works fast (often in hours or overnight), cleans up to 12x quicker than some competitors, and holds up across seasons of salt, brackish, or hard water use without damaging seals, gaskets, hoses, or rubber components. Cleanup is easy—just flush with water—and it leaves no residue. If you're dealing with overheating, reduced water flow, or preventive maintenance on your marine engine or AC system, RYDLYME Marine delivers outstanding, reliable results that far exceed expectations. It's trusted by pros and DIYers alike for good reason—proven over decades, incredibly effective, and genuinely safe. Don't settle for cheaper hacks; this is the real deal for protecting your investment on the water. Highly, highly recommended—grab a gallon and thank yourself later!

Brilliant. Descaled my motor boat diesel engine coolers. Saved £££££s avoiding strip downs of coolers. Inspected cooler internals with inspection camera after flush. Spotless & engine temps perfect.