29' Fountain prop slip
 

Hi guys I wanna hear some others prop slip stories. I have a bravo 1 prop labbed by Brett at BBlades great job. Its a 28 1.5 XR. I took it out today and was cruising at 50MPH and spinning 4000RPM. calculators say this is 29% slippage. thanks in advance......

What speed were you using? GPS or speedometer? If GPS speed that slip% is less than ideal. If that speed was off the speedometer I'd get a more accurate source, either radar or GPS for steady state measurements.

Gps

That's really high. I would contact bblades if they did the work.

What power/HP and what speeds and rpm are you getting at WOT???

77 mph 5350 rpm
525EFI
just me 1/4 tank
gps

That's great speed leave it how does it come out of the hole??

it comes out fine total rebuilt engine 20 hours ago.
if i have lots of fuel and people I’ll throw the 26p on mid summer when the humidity is high.

i wanted to hear from other 29’ fountain guys what they are getting. If it’s normal to have high slip that’s fine.

I would be more concerned with seeing 1/4 tank on a fountain fuel gage-lucky if you have fumes left at that point.

That gets it to 18.5% which is still on the higher side, but your top speed seems about normal. People sometimes get too hung up on slip%. My 28 Pantera had similar slip % numbers. The higher slip will help keep the drive alive too. I would bet a 1/2-1 inch drive spacer would help you also. I increased my drive spacer on my Pantera by and inch and slip numbers dropped some. I picked up about 3-4mph at cruise speed and 1-2mph on the top end and it carried the bow better.

So you increased your drive in the water instead of raised it? I thought for more speed you needed to raise the drive for less drag. I will try props first. The Bravo 1 is 15 1/4" I would like to try one with 15 1/2" diameter and see what that does to the slip numbers.

Think a hydro motive Q-IV is 15 1/2”

I’d like to try the props Brett has made from BBlades
they are also 15.5” i think they were made for sterndrive applications.

The 28 Bravo 1 is only 27 pitch. This makes the slip % at 15.5%. Not a great number but certainly acceptable.
I would consider the 1/2" spacer.
Our 4-SPEED props are very efficient and reduce slip numbers. With a decrease in slip comes the consumption of more HP and a decrease in WOT rpm.
Mid to upper 20's for slip % at cruise with your hull is not uncommon. Slip is always higher at cruise as the boat is more wetted. There is give and take with Labbing. Top speed Labbing does not help cruise. We Lab each propeller specific to goals. We do not do one size recipe fits all.
Many shops do and many do not understand the adjustments to create the determine outcome.

Brett

Thanks Brett,
I’m going to give you a call regarding some 4-speed and 5-speed testers.
i think i want to focus on cruise more than top speed.
Id like to cruise at less RPM and greater speed if I could

I understand 5 blade is better for this option. I could be wrong.....