If you want a professional set up I would speak to someone like Ben at Rutland pumps , he gives good honest advice won’t try and sell you something you don’t need or sell you high prices stuff unless that’s what you want . Honda are a reliable engine , we have had a couple over the years but now have Briggs and Stratton vanguard v twin , much better built ,quite, uses less fuel , and you don’t have to rev it hard for good power just over tickover will clean most things , 21 ltr per muinit and 250 bar will clean most things fast and one pass only with a fsc , if using a lance with turbo nozzle or vario nozzle again it’s very quick cleaning and rinsing , a wheely bin as a bouser would be needed.hose length depends what you will be doing but 50-100 meters should be fine . Smudger does a lot of pw ime sure he can give some advice
I would also suggest it’s not very likely you will get 25 lol from an 13 hp engine / pump as 13 hp wont run the bigger pumps , 21 lpm is the maximum from 13 hp on a good day .