Why emissions are important

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Emissions - why bother?

Emissions compliance is probably the most important issue facing importers and if incorrect can prove very expensive, potentially involving the replacement of engines.

Emissions compliance covers both gas (i.e. NOx) and noise and has applied to all recreational craft imported into the EEA/EU, assessed for RCD compliance on or after 1/1/06.  Outboards have been treated slightly differently to inboard engines/systems but as of now, all engines must comply with both gas and noise requirements.

Under the guidance of the RSG (RCD Steering Group), Notified Bodies (all based in the EU) are allowed to accept engines bearing a CE Mark (for emissions, not power) or for which comparable certification exists.  What constitutes comparable certification is laid out in the RSG guidelines and varies if the engine is CI (diesel) or SI (gas/petrol).  This may include EPA, CARB and others in the US (for gas, the US does not cover noise).

Note that even if the Notified Body accepts the comparable certification and issues a PCA certificate covering craft and engine(s), this does not guarantee acceptance by your local authorities.  In Norway for example the authority (NMD) has until recently insisted on a CE mark and Declaration of Conformity for any engine to be issued only by the Engine manufacturer, something which is clearly not possible retrospectively.  Norway was alone in taking such a strict line but this may change as enforcement increases across the EEA/EU.

Gas Emissions

Marine engines tend to enjoy long production runs (time, not necessarily quantity) and there is sometimes scope to apply later certificates to earlier engines, but only  if it can be demonstrated that the specification (particularly components affecting emissions) has remained the same.

In practicable terms emissions certification in the US started after 2000 (EPA started in 1998 but the way the results are presented makes interpretation very difficult) and as a result it can be sometimes be difficult to prove that engines pre-2000 are compliant.  Some may well be, but without certification this cannot be demonstrated to the satisfaction of the Notified Body.  Before you ask, testing of individual engines is not cost effective as they would have to be taken out and sent to a lab for a series of tests under simulated load conditions etc etc.  Taking the engine down to your local car testing station won’t be accepted.

Manufacturers started CE marking engines in mid-2005 (varies by manufacturer) but even so only those bound for the EU may have a CE plate even when identical to those manufactured for the US domestic market (e.g. Mercruiser).

Generally speaking, Gas (Petrol) engines are easier to certify and it is recommended that if Diesel the engine should be at least 2004+.

CARB (California Air Resources Board) certification started in a limited way in 2001 but realistically can only be applied for 2002+ engines.


Where as the inboard engines sold in the US are accepted to be for all practicable purposes the same as those sold in the EEA/EU the same cannot be said for outboard motors.  Perhaps it's the impression of portability (though with the larger engines weighing 300Kg+ this is misleading), the fact is that Outboard manufacturers will have us believe that engines for the European market are often materially different from those sold in the US.   This makes finding comparable certification hit and miss, potentially to the extent that engines may have to be replaced.  Our advice is clear; before you buy a US engine check whether the same engine is sold in the EU/EEA.  If it is we can probably find comparable certification.  Better still, but an outboard with a CE mark on the engine plate (for emissions, NOT engine power).


Noise is normally not an issue for craft fitted with engine/sterndrive combinations from the same manufacturer, assuming the sterndrive has an integral exhaust (and this is used).  This covers most engines from Mercruiser and Volvo Penta (which in reality is 80%+ of the market).

Craft with conventional/V-drives will however need to undergo a pass-by noise test (which we can do at extra cost) unless a slow speed craft (e.g. Trawler yacht) in which case compliance can be calculated using empirical methods.

Outboards often require separate testing too, since sourcing EU certification for comparable EU engines is often impossible (see comments for gas emissions above) and the US tests don't include noise (yet).

Written By: Rowland Smith

Rowland Smith is a Naval Architect and founder of Gablemarine.  His industry experience includes Lloyds Register, British Shipbuilders Hydrodynamics Ltd, Cammell Lairds, BP Shipping Ltd & Conoco.  He has a degree in Naval Architecture, a Diploma in Marketing (CIM) and an MBA (Cranfield School of Management).  He has also held Director level positions in a number of technology and engineering companies, including CEproof, which provides RCD compliance software to builders. 

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