OK guys, I am so glad you all have more time in front of the computer than me. I have a few more answers from some folks that think they know. I still have some questions though, but first YOUR answers. The plan from G/L shows room for a total of 23" with no rake. My best information is that you need 1" for clearance, any more and you develop increased loss of thrust, etc. The goal is to keep the screw speed way down, like the "big boys" do. The hull is most efficient with a large slow turning screw, ... and that is what we need to tow large, multi-slip docks around the lake(s). If I follow most of the prop sizing programs, it is as though they are gaging for an outboard or stern drive. They suggest a 14" pitch and a 10-12" prop! I have priced props for the "trial & error" method. At $899.00-1,700. per "trial, I don't think I want to do as much "trial" as some would suggest. I did find a site that will rent a prop for a given short period (30 days or less fron out-the-door till returned). Most of the calc programs want a reduction rate and an "engine" RPM. I think that is where I make the program puke. Generally, these motors are wired for 1750 or 3400 for AC, and 1200, 3600, 8,000 (and even 10K) for DC. Granted they are using a variable controller, but if you are wanting to get the most out of the battery, you should consider the "sweet spot" designed into each motor. Most do not even know about this electrical phenomenon. I discovered it when I had wind turbines at my old home. DC is more forgiving, but this is where I am at. I would be willing to settle for an 18", 4 blade screw, that would turn a max of 1125 RPM, push the hull of 4800-5,000 lbs, at the advertised calculated speed of 6+ kts. Reduction rate is variable, and proper use of the battery bank will determine the duration. The 18'-6" could get pushed to 19' if I get a wild hair on the jigging table, and the beam will not exceed the designed 8'-2".
I also read in one of the other posts where somone had a bow thruster in their Titan. It would be great to find out more on that, so I did not have to reinvent it. This would greatly enhance the dock management mission I am building this for. Again, thank you for the responses, and don't be afraid to tell me I am beached. Better to be beached here than on the lake. (and far cheaper)
I have contacted 3 of the larger prop makers with on repies in weeks. I think they thought I was pulling their legs. Ine place said if I sent them $100, they would "engineer" a screw option, and guarantee the report, for my application. Is that normal?
Better, faster, cheaper. Only ever found 2 of the 3! (But still lookin.)
Built 4, repaired 30+, ...So many boats, ...so little time.