Originally Posted by JerseyOutlaw (Post 4473116)

05 25OL, roller cam 525sc, imco neutral box, imco steering, 280 k planes, 28p standard lower, 75.2mph gps

Originally Posted by IGetWet (Post 4475479)

Picked up a 26 LH bravo 1 the other day and got good results from that. But I think a lot of it came from sanding and sharpening the lower unit. I had chipped paint etc on the lower unit and was sanding and repainting too often so I decided to take it down to bare aluminum.

http://i1098.photobucket.com/albums/...4D06799506.jpg
So with same power but box/raised prop cl you haven't quite matched your best speed from before any mods? That was my experience too, I put my stellings box on after talking tp a guy who claimed he had built a roots blower 850 hp baja that picked up 5 mph top speed , I have a theory, only a theory though, IF you take to 6 inch straight edges and hold them on each side of the pad on vee to form a imaginary vee the stock prop center line (mine was 7.5") is really more like 5.5" in comparison to a vee, I strongly feel thats why no matter what prop i tried and even after spacing the drive down 1" with stellings box and when I tried imco 2" shorty my 272 slowed down, would not carry the bow, porpoised etc but this was in the 90+ mph range

After a couple short runs I calculated slip at 7.10 - 8.79% depending on exact rpm, pretty darn good for only 4.25 below the pad. My RPMs dropped because of the better grip, 67 @ 4550-4600. I did see 68 and 69 briefly on my gps but I'm using 67 and 67.5 for the prop slip calculator. The goal for now is to get setup dialed in and then add some HP next season.

Originally Posted by articfriends (Post 4476340)

So with same power but box/raised prop cl you haven't quite matched your best speed from before any mods? That was my experience too, I put my stellings box on after talking tp a guy who claimed he had built a roots blower 850 hp baja that picked up 5 mph top speed , I have a theory, only a theory though, IF you take to 6 inch straight edges and hold them on each side of the pad on vee to form a imaginary vee the stock prop center line (mine was 7.5") is really more like 5.5" in comparison to a vee, I strongly feel thats why no matter what prop i tried and even after spacing the drive down 1" with stellings box and when I tried imco 2" shorty my 272 slowed down, would not carry the bow, porpoised etc but this was in the 90+ mph range

Originally Posted by IGetWet (Post 4476354)

Not sure I follow the theory, the water is coming off the pad, it doesn't follow the imaginary V. My theory on why I haven't seen any speed increase is because I went from a perfectly labbed 3 blade to a stock 4 blade. A lot more drag, weight with the four blade. If I were to have the bravo 1 labbed I should be at or above my old top speed. If the slip numbers are good then I should be able to get the speed once HP is added. Wild Card has stated more than once that he achieved 84+mph with his 600sci and 81+mph with a 525efi, good numbers for any straight bottom V!

But another reason for these mods is a better rough water ride. Before the mods the boat felt like it sat more in the water at speed where now it really feels like the boat is up on top of the water riding across the tops of the waves.

Bblades got back to me today and told me that the 25 rev 4 I had bought was way out of balance, so that should answer why that specific prop did so poorly.

Originally Posted by IGetWet (Post 4473117)

I read your rebuild, looks like a nice setup. What HP do you figure with your motor? What's your propshaft height at 12" back? I imagine your prop slip numbers have to be way down

Originally Posted by Baja Rooster (Post 4478332)

Arcticfriends,

I assume that you had the 272 Performance hull? Did you re-plumb the fuel pick up with that kind of power? Are you completely friggin nuts? Lol

Originally Posted by JerseyOutlaw (Post 4478186)

The x was 7.25 before the box, it's a neutral box. The drive is still deep, so I got my hands on a 3blade 28p from a Warlock V bottom. It likes a lot of trim and some tab. A stock 525sc is 490hp at the prop. It's got a little head work on the intake runners and a custom grind roller cam. It looks overtrimmed, but it runs the fastest this way on a digital gps, pushing the bow up and tab for sternlift. I took the exact measurements for the k planes from my buddy's 25 AT Tantrum.
http://www.youtube.com/watch?v=1PU47GWhypA

http://www.youtube.com/watch?v=3eyVJRHRrDg

Originally Posted by articfriends (Post 4478796)

I modded everything on that 272 from one end to the other, including fuel pickup. Had wiring harness with like 20 extra feet of wire on every lead. redid all that, remounted gas tank where all the screws missed the stringers, bolted seats in correctly, sealed the holes in bilge where water drained thru stringers so they didn't rot out, reinforced gas tank cover in cockpit so it didnt feel like you were going to fall thru, put better motor mounts in and sealed the bolt holes where they bolted in again because no sealent from factory, mounted a second bilge pump where it would actually pump bilge dry instead of allowing water to splash around, Baja guys get really butt hurt when I says these 272's were built real junky when new but its the truth, a little more attention to detail would have went along ways!