Volvo Penta Aquamatic Duoprop vs Outboard 4-stroke December 13, 2021February 4, 2023 Karel Overlaet, RIB Advocate Performance test comparing two Rupert R8s equipped with Volvo Penta V6 280hp vs Outboard 4-stroke 300hp. The test was executed on the Swedish west coast outside of Gothenburg on August 14th 2018.