Analysis of the Underwater Emissions From Outboard Engines

Kelly, Charles (2004) Analysis of the Underwater Emissions From Outboard Engines. PhD thesis, Queensland University of Technology.


The development of Environmentally Adapted Lubricants (EALs) and their use has been gaining momentum over the last decade. It has been shown that raw EALs degrade in the environment in about one tenth the time of an equivalent mineral based lubricant. Estimates and findings such as these serve to highlight the potential benefits of the EAL products, it is also important however to investigate the by-products of their use to ensure that the benefits are not cancelled by an increase of, for instance, combustion by-products. This thesis compares the emissions from a two-stroke outboard engine when using an EAL and an equivalent mineral lubricant, where the primary objective of the study is to characterise and quantify the pollutants that remain within the water column after combustion. To accomplish this, tests were conducted both in the laboratory (freshwater) and in the field (seawater) for a range of throttle settings. A 1.9kW two-stroke outboard engine was set-up in a test tank and water samples were taken from the tank after the engine had been run for a period at each of the throttle settings. The tests were repeated for a 5.9kW four-stroke engine, however, the experiments were only conducted in the laboratory (freshwater) and using only a standard mineral lubricant. Statistical analyses of the results were conducted using a Principal Components Analysis (PCA). A simple dilution model was used to estimate the initial outboard engine emission concentrations, which was extended to determine the concentrations at distances of 1, 10 and 100 metres from the source. An investigation of the Total Toxicity Equivalence of the PAH pollutant concentrations (TEQPAH) was conducted using Toxicity Equivalent Factors (TEFs). Results for both types of engine and in both fresh and seawater showed that even the initial concentrations at the source, in almost all instances, were well below the ANZECC water quality guidelines trigger levels. At a distance of 1 metre from the source all concentrations were well below, and therefore, the Total Toxicity Equivalents of the PAHs were found to be even lower. It is concluded that the emissions from a single outboard engine when using either an EAL or a mineral based lubricant are similar. However, the use of EALs has further reaching advantages in that spilt raw lubricants will degrade in the environment up to 10 times faster than a mineral lubricant. Also EALs are less toxic to aquatic and marine organisms and therefore the benefits of using them has to be viewed from a wider perspective. The results in this thesis for a single outboard engine now form the basis for a more detailed environmental assessment of their impacts.

Impact and interest:

Citation counts are sourced monthly from Scopus and Web of Science® citation databases.

These databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. Some works are not in either database and no count is displayed. Scopus includes citations from articles published in 1996 onwards, and Web of Science® generally from 1980 onwards.

Citations counts from the Google Scholar™ indexing service can be viewed at the linked Google Scholar™ search.

Full-text downloads:

1,179 since deposited on 03 Dec 2008
62 in the past twelve months

Full-text downloads displays the total number of times this work’s files (e.g., a PDF) have been downloaded from QUT ePrints as well as the number of downloads in the previous 365 days. The count includes downloads for all files if a work has more than one.

ID Code: 16448
Item Type: QUT Thesis (PhD)
Supervisor: Brown, Richard & Scott, William
Additional Information: Related dataset available at:
Keywords: Environmentally Adapted Lubricants (EALs), outboard engine emissions, water pollution
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Past > Schools > School of Engineering Systems
Department: Faculty of Built Environment and Engineering
Institution: Queensland University of Technology
Copyright Owner: Copyright Charles Kelly
Deposited On: 03 Dec 2008 04:03
Last Modified: 28 Oct 2011 19:48

Export: EndNote | Dublin Core | BibTeX

Repository Staff Only: item control page