Hello, We have a 2004 Sea Ray 340 with 8.1lt V-drives. We purchased it last summer and besides replacing a few bad sensors, it has been rock solid in reliability. We take it out every weekend and have ventured down to key largo and Islamorada multiple times from Fort Lauderdale. I've been doing all kinds of research to increase performance and efficiency for those longer trips. Those test results on boattest.com were from a sea ray 340 with Bravo III sterndrives. On the V-drive setup, factory propellers are 18" x 4 blade with a 21 pitch and my experience is a top speed of 38 mph at 4700 rpms and a good cruise speed of 28 mph at 3600 rpm with this factory setup. The boat always felt like it had a lot more potential. Mercruiser's recommended WOT RPM on the 8.1's is 4600. I was over revving a bit and the boat felt like I could get a better plane at a lower rpm, almost like driving an old muscle car down the highway with 4.11 gears. A ton of acceleration, but revving too high when cruising and top speed. At 28 mph, it felt like the bow was still riding a little high and it was still climbing up hill like it wasn't completely on plane. I like to bring the trim tabs all the way up during cruise for less drag. I notice a speed difference if the trim tabs are down. If I brought the RPM's up to 3900 or 4000, the boat would flatten right out and really feel like it was skipping across the water but cruising at 4000 sucks fuel and I feel is extra wear on the engines. I'm sure when Sea Ray decided to use this prop setup, they factored in the boat being fully loaded with 12 people and gear, etc and they needed a safe prop to run for the masses. They run these same engines in the 380 and bigger I believe and I feel there is a lot more potential to be explored with this boat and I think it's just finding the right prop setup. If I could go back I probably would have looked more for an outdrive setup and getting a boat lift as you do gain a lot more speed and better GPH due to the lower resistance of the stern setup plus having the added comfort of being able to trim the drives up when it gets shallow. I've stirred up a bit of sand a few times cruising the keys trying to explore some of the natural islands. Here is an article I found wile doing my research and it is a very good read if you are on the market for a boat like this.
http://www.searay.com/boat_graphics/electronic_brochure/company22491/TST_9.pdf
I started to experiment with the props when I had the boat hauled a couple of months ago for bottom paint. I decided to have the propellers pitched to 22 vs the factory 21. For some reason my mechanic strongly recommended against this along with the propeller shop. I had a bit of an argument with the guy at the propeller shop because they told me according to their calculations, I would loose 200 rpms at WOT and I would be putting to much load on the engines, however, I had this very strong gut feeling that re-pitching would be a benefit. After launching the boat with the newly re-pitched props and fresh bottom paint, I was more than happy with the results. The boat still jumps on plane as it always had and when I bring the RPM"s to 3600, the boat flattens right out and skips across the water at a very comfortable and efficient 32 mph. Top speed breaks 40 mph and I'm still revving 4600 to 4700 RPMs. I'm assuming a fresh bottom paint job helped a bit but I still feel there is a lot more room for improvement. When I open it up to WOT from cruise speed, the the engines thrust the boat forward without any struggle. These really are big engines for this size boat. I will be purchasing a set of ACME propellers soon and with their precision manufacturing process, I'm going to step it up to a 24 pitch and see what happens keeping the ones I have now as spares. My goal is to have a comfortable 3600 RPM cruise speed at 36 mph or higher. It seems the boat really starts to suck fuel over 3600 rpm. I'm not too concerned about top speed but it would be nice to see the boat crack 45 mph which I feel very confident it will. I'll keep you posted when I do this with results.
