Thermoelectric energy (TE) harvesting is a promising solution for waste heat recovery onboard ocean-going ships. Recent studies have been conducted on thermoelectric generator (TEG) optimization considering heat exchangers and thermoelectric module (TEM) improvements. However, they mainly concern separate optimization of system components. A test rig has been designed and built to test the performance of the TEG on engine operating points representative of marine application and quantify the impact of the clamping pressure on efficiency. An analytical study on the effect of applied pressure on heat transfer coefficient has been made for tendency prediction. In a first step, two types of commercial TEM have been studied separately on the test rig. The engine data were extracted from a Diesel engine that shares the same principles with marine Diesel engine in terms of engine efficiency and exhaust conditions. Results showed an optimum clamping pressure for the TEG device corresponding to a compressive stress of 0.35 MPa. These results were coherent with the predicted ones in the analytical study. The Bismuth-Telluride TEM showed a 70% higher power output compared to Silicon-Germanium TEM, but rapid deterioration of the TEM occurred when air inlet temperature in the TEG exceeded 300 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.