These are all 30hp though. I don't have a cav plate, I'm satisfied with current performance with the 3 blade power tech prop, wouldn't want to potentially sacrifice any speed. Ankledeep runs a 4 blade he likes it. Any aftermarket with cup will be better than the stock without question, the stock prop will be as close to unusable as you can get. Mel ran his test boat with a 20 I think, Erin could probably give you the skinny on the prop they used. Congrats on your upcoming build.
Great, yeah I did a little search as best I could and couldnt find a 25 thread... Ive got a stainless 3 blade with a little cup on it just coming back from being rehubbed from my duck boat, and wanted to see how everyone was set up. When I was at the factory, they said i didnt need a cav plate, but I wanted a few more opinions. Thanks for helping me save a few $$$! Hopefully when i finally get to run it, I wont have to add it later.
Took me quite a while to get dialed in but what I ended up with is a solas new saturn SS 12P with a Bob's machine shop true tracker cav plate. I cruise at around 22 with that setup and WOT @ 24-25 with two anglers and 6 gallons of fuel (no battery, coffin box, console, etc on mine). With three anglers and 6 gal I am very close the same perf numbers. probably going to get a 13p new saturn before too long as well because I am running 5500+ rpm's with the 12P.
The Bob's true tracker makes a huge difference in cavitation issues, especially in aerated water. Also holds the boat at a nice angle. My motor is set at second hole and plate is same angle as boat bottom; sits dead level with water when boat is empty). Before the cav plate I would blow out in turns and any kind of rippling current with my SS three blade. I rarely have blow out issues now. With my four blade solas amita 12p I can run without the cav plate and not blow out often, but that prop is slow giving me a cruising speed of 19-20 and not much more WOT. The performance with the 3 blade stock aluminum isn't worth writing about...
You can get the solas props at iBoats for good prices. http://boatpropellers.iboats.com/propeller-showcase/solas/
I love my shadowcast 18 and the ability to run shallow is definitely one of the things that drew me to it, but it was a PITA to dial in and I don't think the factory has quite got everything fully figured out just yet prop wise, but I recommend 3 blade solas new saturn with anti cav plate, 12P if you have it fully rigged out, 13P if you are keeping the lay out simple like mine. The new saturn also has a little cup to it so chances are a cav plate and your current prop will be a good match.