Hello, I'm using a Yamaha 13x19 on my TLDI, top speed is 39 knots @ 5750 rpm whereas the Standard Tohatsu 13.75x17 kept me under 5250 rpm. Yes, I know, it's weird to get more rpm with more pitch but Tohatsu may have its own way to calculate props.
Since my boat is 5.8mtrs long, you can probably expect more speed than your 38 knots with a Yamaha prop, better yield.
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