Mine is Highfield OM540DL.
Transom and engine are XL.
Evinrude 115 HP is max possible for this boat according to boat plate.
Prop Steel 3 blades Viper 19p for lakes and Rebel 19p for offshore.
We are 5 people and I observe that Rebel which has bigger diameter than Viper is too big for 5 people family so bought used 17p Rebel from US.
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I hope that in Australia you can ask dealer to check for prop and maybe they have some DEMO props ? Not possible in Poland
Sjipyard who sell me Etec and install on Highfield made some tests after 1 y of the use and advice is that this flat end behave differently than deep V to the end and they suggest lower engine position