We went 72.5 today with the 25P M+. I really think we need more prop before we'll see some real numbers. It hits the rpm quick. We did get over 5K today also. I think I need to trim more to get the rpm and speed where it needs to be. We'll see the numbers we want for sure with the right prop. I don't think there is any way we'd see them with this 25P.

We did smoke a Sunsation today though!:D That made it worthwhile right there. It looked like a 28. I couldn't tell if it was a single or a twin cause I never saw the back end!:cool-smiley-011:

where do you want rpms at top end?

Storm, I think he said 5300.

J., were you able to go WOT?
Is the handling with the 3 blade too crazy?
From what Dave M. has said, those step pad 24's don't like the 3 blade.
I'll send you that Mach 4 blade tomorrow. I still think you need to find someone local to let you try a 26p and or a 28p Bravo 1.

Storm, our peak HP is 501.3 at 5200 rpm. I think shooting for 5300 would be right on.

We did go WOT for quite a ways. With the 3-blade, she was steady as a rock at speed. In fact, the only time I've ever tried a 4 blade, the boat handled terribly. Early this season, before the full hydraulic steering and with the worn gimbal ring, we tried a 24P Bravo one. The boat pulled HARD right when coming back down from speed, and pulled right at speed as well. I'm hoping that was solely because of the steering issues and a 4 blade will work well for me.

The boat feels like it is moving faster than the GPS is reading. With the scream of the engine and the seat of the pants feel, it feels much faster than it did with the old engine. That being said, I think with enough prop, we're going to see the speed.

Sounds good so far.
I think you'd be shooting for 5100-5200 though.
Why try to go over where peak HP is?

Pat, if he's just over 5k w/a 25p, you think he'd clip 5200 w/ a 27p or 28p?
But imo, its all worth trying... its the only way to find the right one.

Jay, i know what you need...
to take the boat to lake-x for a weeks vaca of testing. :D

Jay,

With your HP and being a step hull I think a 28 B1 is your best bet. I turned a labbed 28 right at the rev limiter (4900) with less HP.

Do they do things like that at Lake X? Can you call up and schedule test time as a person in the general public? I can't even imagine what that would cost!

T, I think the 28 B1 will be where we wind up also. It seems that everyone with these boats and good power wind up with good numbers in that range.

Yea, I think 5200±100rpm.

Some times boats will run faster with a bigger prop. It depends were the engine hits the wall.
When I had a 310HP/7.4MPI in my boat, it ran faster with a 26p B1 then with a 24p B1. With the 24p, it would not pull past 4600 and with a 26p it would pull 4400 and go faster.
My 502Mag MPI seems to make its best power above 4800rpm even though the WOT range is supposed to be 4600-5000. With a stock 28p B1, it will spin 4700-4800 but it takes a long time to get there. With a 26p it pulls like mad all the way to the limiter. The labbed 28p pulls great and goes the fastest.
Test, Test, Test, is what you have to do.

Lake-X ???

Prop testing tomorrow. We'll be trying a 28 Mach, a 29 Hydromotive 4 blade, and a 26P Bravo 1 labbed. I also believe I've figured out that I am not trimming near enough to get the speeds. Last week at 72.5, the boat was rock solid. Everyone says that I need to trim until the boat gets a little loose and fine tune from there. I didn't want to push it as 1) my trim indicator still needs adjusted and I didn't have a real good idea where we were, and 2) I'm a little over protective of my drive! My big thing is that this boat has zero bow lift. At 72.5, it looked to me that the bow was pointing almost downward. That can't be helping speed any. Is more trim the solution to that one? What else can be done for bow lift?

We're going to give her a sound thrashing tomorrow as the engine builder is going to ride along and check fuel pressure under load, and also compare my tach to a second tach to verify rpms. I'll let you know how it works out.

You must have not trimmed up nearly enough during your last tests ride. A 3 blade mirage plus has about as much bow lift as any prop there is. The Mach 4 blade is a vary neutral lifting prop; just trim until you go the fastest. A Bravo 1 is also pretty neutral and may have a little more over all lift depending how it was labbed. If the Hydro you are going to run is a QIV, don't bother, it's a stern lifting prop.
What I find to be about the best trim is just before you start to shoot a rooster tail. Another way to find max trim is to run at about 60mph and trim until you start to loose speed and then trim back down a bit. Don't go by the gauge, go by how the boat feels, then look were the gauge is for future reference.
As for your drive, it's not going to break unless you mash it out of the hole or don't throttle back when you fly the boat.
Have fun and be safe...