Trouble: I've seen this posted by you on some other sites as well. #1 4000 rpm's at WOT would indicate wrong pitch prop of which makes the engine work harder. IE. more fuel consumption. Engine should turn 42 to 44 hundred wide open or up to 45 or so with one person and full fuel. Not sure, but I'll look in to what capacity tank is in that particular boat as well. #2 The replies you got over there are valid for the most part. There are a lot of variables such as choke, carb, state of tune, compression and general cond. the engine is in. Hope that helps. Any questions or help you need let me know. 165, 170's or 470's basically the same motor they are usually pretty good on fuel consumption if all is well. All tho they did have there problem's as any other engine does.