Twin Diesel Marine Cummins

“We have a recreational boat with twin 8L Cummins marine engines. They’re 21 years old, but only have 1780 hours total. Over the years we’ve done regular oil changes and maintenance. We thought that was enough, but it seems that was the downfall. The boat sits a lot (obviously) and has a lot of long periods of low speed/low load getting it through the ship canal and locks to get to the ocean. Summer of 2021, one engine started to smoke a bit, and would run on only 5 cylinders for a few minutes after starting. Replaced the injectors hoping that would fix it. It didn’t. Last summer (2022) it got worse – that engine was slow to start, smoked more, and started using a lot of oil. Fall of 2022, we took the boat out after servicing for a short run. It began to knock and bang HORRIBLY, so we limped home. Tested compression, the Starboard engine #1 cylinder had 0 compression. At tear down, it was blatantly obvious that the rings had carboned up and broken, then the piston slapped around and broke, destroying the piston and liner. With only 1780 hours!
We in-framed that engine, and to preserve the port engine which was smoking and getting harder to start, we have used Flushing Oil Concentrate, and are using FTC Decarbonizer and ULS Diesel Enhancer in the fuel tanks, and AW10 Antiwear in the old port engine. Results so far – the engine oil in the port engine remains very clean after the flush, the starboard/rebuilt engine will get a flush after it has bedded in. After adding the FTC Decarbonizer to the fuel, I noticed RPM picked up immediately and the engines idled more smoothly. Last Friday (before fuel treatment), the Starboard engine (just rebuilt) turned 2515 RPM WOT and the Port turned 2435 RPM WOT. Today, after adding the diesel treatment, both engines turned 2530- so we are picking up a few horsepower for sure! I’m sure the AW10 is helping with that also! With these engines, gaining 100 RPM is not insignificant. I can’t wait to see further improvement with a little more time.”

John E, Bellevue, WA