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IMO Tier III-Certified SCR System Is Simple to Install, Operate and Maintain

An enjoyable, hassle-free yachting experience — that’s what the new 2433 mhp Cat® C32B marine engine delivers, even when your vessel is traveling in Emissions Control Areas designated by the International Maritime Organisation (IMO) or docking in a growing number of ports with their own emissions requirements. Just order your C32B with a fully integrated, IMO Tier III-certified aftertreatment system designed and manufactured by Caterpillar.


IMO Tier III regulations took effect on January 1, 2021, for newly built recreational vessels longer than 24 meters and require reductions in NOx emissions of 75% compared to Tier II standards. Achieving this significant decrease calls for the use of an exhaust gas aftertreatment system on a vessel’s engine.

Caterpillar’s answer is selective catalytic reduction (SCR), which reduces NOx by converting it into harmless nitrogen gas and water vapor. Diesel Exhaust Fluid (DEF) — a carefully blended solution of high-purity urea and de-ionized water — is injected into the exhaust system, where it decomposes into ammonia, then selectively reduces NOx with the help of a catalyst. It’s a simple, proven solution that makes emissions reduction worry-free.


With most engine rooms already small, we didn’t want the C32B’s aftertreatment to take any extra space away from living quarters. So we worked closely with shipyards and boat builders to make sure our SCR system is as small and flexible as possible, with multiple orientations to fit different boats. (It’s also an airless system, not air-assisted, so there’s no need to supply compressed air onboard.)

Having SCR onboard doesn’t change anything about the way the C32B operates. Built on the already reliable C32 platform, the engine won’t lose power due to any unlikely issues with the SCR system. And when the vessel leaves an Emission Control Area, the captain is free to turn off the SCR system and the C32B will meet IMO II requirements as well. There’s minimal maintenance required — just a DEF filter to change during other routine engine maintenance. And the Cat SCR system is designed to last as long as the C32B itself, eliminating an additional service or replacement interval that would require taking the vessel out of service.

IMO Tier III regulations are all about NOx emissions, but there’s a carbon-reduction advantage to the Cat SCR system as well. Using aftertreatment to reduce NOx allowed us to fine-tune the C32B to run as efficiently as possible — which means your engine is likely to burn less fuel overall and generate fewer carbon emissions in the process. Another added benefit: The Cat SCR system decreases sound from the exhaust for quieter vessel operation.

Ready to learn more about the advantages of the Cat SCR system — and all the enjoyment-boosting, hassle-reducing features of the new 2433 mhp Cat C32B engine? Talk to your local Cat dealer.