tdpb2008

I have a 30' cobra terminator cat I had just bought it has a hp500 500-540hp it has a bravo 1 1.36 ratio and a 26p bravo prop, at WOT I'm getting between 3500-3800 rpm max @ 55-58mph I'm not sure if I have a timing issue fuel issue or if it needs a 1.50 ratio drive it planes out strong then falls on it's face at 3k rpm

Looking for some help

I am going to swap the 1.36 drive out with a 1.50 this weekend to see what happens

Any help would be appreciated

Quick2500

Wouldn't it be easier to change the prop?

Griff

I would certainly check the timing before swapping drives.

With proper slip% and a 1.36 ratio drive and 26" prop it should run about 80mph at 5000rpms.
I don't think your issue is 1.36 ratio. You could drop down in prop pitch. It will have the same effect as swapping to a 1.50.

Tinkerer

You don't have enough HP or Torque to spin that prop to 5000 RPM. I have a 26 ( actually 27 ft ) Daytona with 650 HP ( 509 CUBES ) and the 1:34 ratio drive and a labbed 30 Bravo at 5400 RPM.

But saying that - I think there is something wrong with your engine. The fact that it comes out of the hole well and then falls flat tells me something is holding the RPM's down. How far below the lowest point on the bottom of the hull is your prop shaft. If your prop shaft is real deep you are going to have to trim way up to get the boat to fly. If your prop shaft is more than 2 inches below the hull and you still want to change the drive I would try a -2 shorty if you can get your hands on one.

JRider

iTrader: (1)

I'm not sure the boat will do 80 being a single 30 with HP500. 24 pitch is easier than changing drive

airjunky

iTrader: (2)

Dang . If your holeshot is good on a 30 cat with a 1.36 ,26 prop and what should be a combo that has more of a top end powerband flavor my vote goes to the fuel pressure gauge .or your tach is way off

tdpb2008

My prop shaft if level with the bottom of the sponsons, I do have a -1 imco that will go on it shortly it's a 1.50 ratio, it's had a 750hp blower engine before but not sure what he was running for a prop

tdpb2008

I have two 1.50 drives available to swap no problem and not many props that's why I was going to swap a drive

tdpb2008

Checked the tack to a timing light and it's within a 100rpm of each other

airjunky

iTrader: (2)

Hows fuel ? Secondaries opening on the new motor (if carb) sounds like your familiar with boat and wouid know if its a dog out of the hole ,pulling highway gears . If your leaning out its not good for the motor long term