Torque and horsepower will always cross at 5250. Hp is a multiplier of torque. Prop for peak hp. Then you can play with props for slip and handling characteristics. If you’re spinning a 26 to 5200 and peak at 5400 landing the 26 shoul get you there.

Based on those numbers you listed you’re at 8% slip. That’s phenomenal.

Oh. Sorry that wasn’t mentioned in first post. Raise the limiter so you can use the hp to 5400. Is your current prop sitting on the limiter?

Ok. Let’s go back to basics. Carb of fi? If you’re on the limiter you’ll hear it. If you’re on the limiter you need a larger pitch. If you’re not. You’re very close.

The prop will mess you up too. Always be careful of previous owner claims. Ideally you bump trim speed will increase. Keep bumping slowly until speed starts to decrease. Then bump back down. Lol. That’s the short version. I would stick with the 4blade. Again you’re showing 8% slip which is phenomenal. Maybe look for a new 28 hydro to test also. Thatll drop 400 rpm so you’ll know if it’s a limiter issue. Every inch of pitch I worth about 200rpm.

I personally wouldn’t worry. I mean if you already bought it you can try it. The 3 blade may be able to give you a tick more on top speed but overall characteristics most like the 4 blade. It doesn’t hurt to try. Then you get into a more round ear bow lifting prop like a bravo or a cleaver style stern lifter like a QIV hydro. Fountains do a great job carrying the bow in hull design and seem to really like the hydros. Plenty have had good luck with bravos also. To find the “perfect” prop requires a ton of testing and the perfect top speed prop won’t be the same as the perfect all around prop.

Try a Hydromotive P5X. That’s what Tom Bucknell, the owner , recommended, Generally, more blades have better hole shots and higher cruising speed. Your slip is real low and you may already have your best prop. You might try trimming the boat a little more. 690 HP should push your boat a little faster than 78.