Re: Volvo Penta Dual Prop size ?
What year is your boat? I am thinking it has a DP-A or similar (white) drive? Are you sure it is a B5 set? What altitude do you run at?
My gut feel is to not go lower than the B5 set. Most boats this size came with the B7's I think.
Your numbers sound pretty close to ideal actually when considering that the tach accuracy may be off some. If you go to a B4 set the holeshot may be better and your top rpm's about 200 higher but you would not gain any top speed in my estimation.
What are you wanting to accomplish? Stay on plane at lower speeds? Pull towables better when loaded down? Or are you just worried about lugging the engine? Is the boat loaded down when you get those numbers?
My 22 foot Cuddy gets 46mph with 4400-4500 rpms with B5's. It is a VP 570 which is fundamentally the same as AQ271C, a 5.7 4bbl with 275hp at the crank, not sure what it converts to at the prop shaft but I guess 230-240. It will hit 45 even if loaded up.
By the way, the reason I asked if you are sure you have a B5 set is because when I compare your numbers to mine yours shows that a slightly higher pitch is in play, like a B6. B5's are about a 23 pitch, B6's a 25, B7's a 27.
Mine came with B7's but the B5's work much better for us as we frequented a small lake and use it primarily for tubing, not much day trip cruising as it only took 5 minutes to get across the lake!
