More Data
 

1.5 Ratio

78 MPH, GPS

4650 RPM WOT

4500# Boat, fuel and me

24' Pantera V bottom

1' Chop, 10 - 15 Passes

Engine specs are above. I should be able to turn this prop easily.

the number you are using for your x is a number that the factory uses...tell us the measurement from the bottom of the boat to prop shaft centerline (like 3 1/2")....with the shaft parallel to the running surface. the other measurement requires me to use transom angle to calculate.

you can toss HP all day long at an ill set-up boat and never go faster. I think the problem is much deeper than the prop...hummm a pun perhaps :D

Man that is only 5% slip!!! Are you sure you aren't at a 1.36 ratio? If so you would be running around 15% slip and that would be much more realistic and may explain why you are having problems turning that 28.
Good luck!
Craig

XZ 1.5 Drive on the way!!
 

I believe its a 1.5 ratio, thats what I was told by the factory and previous owner. Wouldn't it be on the serial number tag? I can verify.

I will be receiving an XZ drive next week, 1.5 ratio for sure.

If mine is a 1.5 what else could be the cause? The X dimension measured is stated above, I will measure bottom of boat to shaft this weekend.

Your Drive can not be a 1.5...
You would need a 30pitch prop to go that fast at your RPM.

My 24' Pantera only had a 305HP/454 and would spin a 24 at 4600 and go 63gps.

My 24' Superboat has a 310HP/454 and spins a 26 at 4400 and runs 66gps.

Try a 26 and you will crack 5000rpm and be going over 80mph.

What else are you dragging in the water? Trim tabs, offshore water pickup, speedo pickup? Do you have a nosecone?

Do you have any good data from before the engine was redone? That may lead you to where the problem is. Double check the tach with another shop tach or known calibrated tach. The best slip numbers I can get are about 10% with a bravo1. Good Luck

Only have trim tabs. Speedo pick up in the drive. No nose cone.

I'm going out today to verify gear ratio, I'm positive its 1.5. I have another tach, I'll try it, but the one in the boat seems right as the engine is definately not up in RPMs at WOT with the 28P

Definately a 1.5 ratio. I can't get a good measurement on the drive, looks like 5-3/4" - 6".

Any other ideas?

If your propshaft is that deep, its WAY TOO DEEP. You sould be in the 3"-4" range. If the X is really at 17 1/4 then it should be in that range. My X on my notched transom 28 is set at 20 1/2. I have a 3" drive spacer that lowers the propshaft 3" and does the same thing as changing the X to 17 1/2. My propshaft is 4" above the bottom.