So this year a repowered my 10 meter fountain..So About three years ago I put bravo's on it set the drive height at 21 inches and put the motors 32 inches apart. I had 454's making about 450 hp. I would spin a 26 bravo one non labbed. It would run high -mid 70's. At 4000 rpm would run 58-61 0n gps depending on the load . 79 at 5200 ..76 at 5000.. Now I have 540 tall decks mild hp 575hp.. I put a brand new set of 30's untouched just like the 26 bravo's and I can't even get it on plane. They blowout bad at 2800. I did get it on plane once and the slip numbers were 23% ... 3500 rpm 50mph and at 5200 rpm 76mph .. I didn't even try to trim it more. It also rode very flat felt like a turd. Why don't the four blades work now???? The power is the only thing I changed?? Are the higher pitch props less efficient ?

Try a 1" spacer, I believe I read that anything over a 28 bravo is pretty inefficient

Time for five blades?

That's what I'm thinking but why do the 26's work and not 30's

I'm spinning 30' on a Regal Velocity to 4800, and they don't blow out at all. You have a lot more power then me, and were only 5 mph slower with 90 hp per engine shy of what I'm running now, previous (when you were running the 26's). I'm leaning towards the combination of the bigger pitch and the extra 200+ ft/lbs on each motor, it's enough that the props can't get enough water to hook up anymore.

If it's running very flat, it isn't getting the lift required from the props to carry the bow. I'd look for a set of 5 blade Maximus props, or even the 6 or 7 blade herrings to try. End of the day Brett at Bblades will have your answer, he currently has a set of 30's of mine.

Sounds like you have a very aggressive X dimension and now that your putting a good portion of power to it, the props won't hook up. As lil red said, dropping the props in the water will help them hook up, but I'm going to go on a whim and say so will extra blades. If your photo is any indication of throwing a rooster tail while running, your X dimension has got to be at least two inches higher then mine, as I barely get prop spray when WOT from my 30's.

Did you try your old 26's before you went to the 30's? I would try them first to get a base line to compare to the old power. 4 steps up is a big jump. It's been my exp that Bravo 4 blades are ok up thru 32's but the geometry gets a little wonky with the 34's and 36's. I'm not sure what you mean by 21"? What is the depth of your props center line below the hull? Thats the critical measurement. You might not be deep enough and Bravo props are not good surface drive props. Blade style might be an issue but probly not if both 26's and 30's are both Bravos. My boat did not respond well going to 5 blades, its not as simple as thinking by adding another blade will help blow out.

I sold the 26 four blades I use to have on the boat but I have a set of 28's that a tried once and they were juat alittle too big at the time but they got up on plane fine. So I am going to try them this weekend..

Hello Excalibur82,

The explanation is not that complicated. You added a huge amount of torque, and also went up to 30" pitch. The 30's are trying to hold the rpm down, which allows the engine torque to climb. The torque goes down as the rpm increases, and goes up as the rpm decreases. Take a look at a dyno sheet on your engine, or any engine for that matter.

The 28's will do better, but with the 21" "X" dimension, and the torque of your engine, we definitely recommend the P-5 X five blades. The Maximus is too large in diameter, and the cost to cut it down and tune for your application will be cost prohibitive. The P-5 X is ready to go box stock, with a 1 year warranty and a 30 day return/exchange program.

Thanks,

Thom

Excalibur82,

Are you sure the 30's were untouched? I hear that all the time only to find out they were repaired once. Repairing without knowing the exact geometry of a propeller is a quick rout to poor performance.
The 30 Bravo 1's should have worked fine with the power modifications you performed.
a 21 inch X dimension won't be affected worse by 30 pitch props in most situations. The 2 inch difference in the Bravo family shouldn't play a part in the depth you are running. Torque of blower motors is different from NA so it would have been nice to have tried the old 26's.

P5X's are a option but so are true Bravo 1's that haven't been touched as well as stock Maximus props. Maximus props most likely will be the ultimate propeller but "might" be the best with some type of adjustment. I'm not sure I would state the cost to adjust the Maximus props is prohibitive when Thom doesn't know what might or might not need to be done to them. Also, we let the customer determine what he or she thinks is cost prohibitive.

Also, we have a test program that allows you to test without buying. Both the P5X and Maximus props are in that program. With the other program mentioned above, you must purchase props first.
Let us know if we can answer any other questions.

Brett

I just bought the 30's they are brand new . I have not tried the 26's but I think I might