I have a 22 foot Hydroswift cuddy, fairly heavy boat and I am at altitude in Denver area. 290 DP 1.95 ratio. The original 5.7 with aluminum B5 props which are 21 pitch it would top out around 4600 rpm and 43 mph loaded with people and gear. Built a non vortech 383 with camel hump heads, pretty close matching roller cam, original Holley 625 vacuum secondary carb, 9.5 pistons. It now will easily blow past 5000 rpms. I backed off at 5300 and 48 mph GPS. I put on the Stainless F6 props which i understand are 23 pitch. It went past 5000 and I again backed off at 5300. 53 mph GPS. The last time that boat saw 50 was when I first bought it and I took it out by myself, 1/4 tank and nothing in the boat. Lake Powell at 3700 feet the stainless props were obviously too low in pitch and made great ski props. I need a set of F7s but I don't think they'll be enough to limit the rpms. At least not at lower altitudes.
This coming winter the engine is coming out and vortec heads and intake along with proper cam will all go on. Compression should go to 10.5. I will have to manually limit top rpms. Duo props aren't cheap. Top speed is fun but feeling that acceleration no matter where I punch the throttle always brings a smile.
Total cost for me was around 4K which includes new stock Volvo exhaust manifolds and risers. Stock Volvos too. I may or may not buy a set of performance exhaust manifolds but I refuse to install through hull exhaust so I am limiting total performance. I had to pay a shop to remove and install the engine total cost was 350.00. I had everything disconnected, drive off,motor ready to be yanked.
Why do I do this? Because I can.
