Griff

You're using the wrong prop. Try a 24 Bravo 1 4 blade prop or maybe a labbed 26.
My guess is it should run upper 60's when dialed in correctly with an HP500.

jens henrik

This summer i have testet a 25` Revolution 4. Is that prop not very similar to the Bravo?? Why do you think that the Bravo is a better choice??

MichiMike

Mercury says the Rev 4 is recommended CC outboard boats.

Mercury also states the Bravo 1 is for high powered sterndrive boats........ FWIW

Baja Rooster

iTrader: (1)

I *think* the Bravo 1 has more stern lift as to where the Rev 4 has more bow lift.

jens henrik

Thanks for the info guys.... I appreciate it..

Griff

The Bravo 1 has more bow lift than a REV4. It will carry the bow more with less trim. Slip should go down.

Gun Slinger

Im running a 29 with twin custom 427 big power small blocks, pushing way into the upper 90's low low hundreds with 32's It's not so much just power that you need with this boat, its matching Torque. Seems like you have a good motor to start with, needs big heads, big cam, maybe a huffer on top if you want to get into the high 70's-80's. Keep in mind it would be wise to forge out the bottom end as well for extra security.

Another option per Larry Smith is to change the X dimension with a box and play with the length of your bottom end of the drive. What people are saying is correct, its a heavy boat for a single, you need to get the ass end up out and on top of the water.

jbdykes

iTrader: (1)

I had the same issue on my 27 Donzi 27 ZR. Believe it or not, a spacer solved the problem. Installed a new 525 and the boat ran 73 (about 26% prop slip). I added a one inch spacer and got no real difference in performance. After the 1 in spacer and 28 p four blade, I tried a 5 blade. Because of hitting the rev limiter, I went with a 29p which should have and did knock the rpm's down 500. That solved the rpm problem, but the performance was the same. I only got 73 on gps. Hole shot wasn't any better and cruise about 42 mph on gps.
Next step was to change the spacer to a two inch. That solved a lot of problems for me. I started with the 28p, 4 blade and got to 75 mph before running out of lake. Water was very choppy and it was a very windy day. Higher speeds were definately obtainable if I had had more room to run. Notably, the hole shot was great and cruise improved to 45.6 mph.
Next, I tried the 29p 5 blade. It was a pig getting out of the hole and still only ran about 73. A lot of that was due to the prop finally being fully submerged. I'm either going to sell it or have it worked to a 27p and use it for a back up prop.
I also ran a 27p 3 blade just to see what the extra bow lift would do. Again, only got 73 mph, but that was in part because I was too busy holding on to the boat! It was a wild ride, and I don't recommend it.
I'm very happy with the 2 inch spacer/ 28p b1 4 blade. All my test runs were in fresh water and I believe that when I get it back in the Gulf, I'll see 80 mph.
And as an added note, I had 4 adults and a child with a full tank of gas, on yet another windy, choppy day and still had good performance. Good hole shot, 45 cruise, and hit 73 mph.
All in all, a vast performance over the 496 ho where I only got to 64 at WOT with a ton of prop slip.

MDonziM

One thing no one has mentioned yet is your nose cone. A standard bravo 1 lower is hydrodynamic to 80mph as many high perf boat guys will tell you. This can throw off all of your current prop testing results. I don't know the scarab 29 but if you take a light 22 donzi classic with a 415hp 502/ bravo 1.5 and a mirage plus 25" it will do 70-72mph at 5000 rpm. Put a nose cone on and it will probably slow down. I have nose cones on my 27 magnum but that is because it is rigged with a high x dim and it has twin 550hp big blocks. At 82-84 mph maybe my cones add 1-2mph, but they also increase stern lift as do my bravo 1 32" props which my boat/setup needs. Most people looking for stern lift have twins, but again it depends on the hull.

It might see m counter intuitive but I bet you should remove your nosecone unless you want to change other variables on your setup.

Griff

On my 28 Pantera that I used to have, it had a nose cone when I bought it. I thought it might be contributing to high slip numbers.
Swapped to a new standard case and might have gained 1mph at best.