Changing prop pitch

S

Shadowcruzr

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I have been running 24 pitch props on my Bravo 3 since I bought the boat new in 2000. The boat has run fine all these years, just has a very slow hole shot and doesnt reach full WOT.

I am finally in a position to afford new props and was wondering if switch to the recommended 20 pitch would cause any problems?
 
Contact a local prop shop with DP experience. They will need to know what your current WOT is in order to make any recommendations. A good prop shop will allow you to borrow props to dial in the correct RPM.
 
A 4" drop sounds like a lot. I have inboards and I know it's different but I dropped 1" of pitch and it made a big difference for me.
 
My current WOT is 4200 and it should be 5000.

I'm wondering if the switch will cause any engine problems.
 
I dropped from a 28" on my Bravo III to a 26", and I gained about 400RPM. I was at 4200, and now I'm at 4600, right in the middle of the recommended 4400-4800.
 
Based on Bob's results, the DP seems to have roughly the same range of drop as a single prop. WRT your damage quesion; the answer is no. What model engine do you have?
 
Paul,
David is right, going down in pitch on your props won't cause any engine problems. However, running props that don't let the engine reach the recommended rpm range COULD damage your engine. You mention 5000 is where it should be, but what is the rpm RANGE(ex 4800-5200, 5000-5400, etc)? I's important to be propped correctly.
 
Sounds like you have a 5.7L B3...with a boat that heavy you will never get a great hole shot with a small block. I had 22P on my 'built' big block and went to 24P props...dropped 400 rpm.

Sounds like you may need 20's, and I'd do this soon - your lugging your engine.
 
I have a 300 hp 5.7 MPI engine. WOT range is 4600 to 5000. I got screwed by the dealer when I first bought the boat. COuldnt afford a replacement set of props before. I tried to see if there was anyone wanting to swap.
 
Look used and sell yours - should be an even swap.

You have been VERY hard on your engine all these years.
 
quote:
Originally posted by Shadowcruzr

Anyone heard anything on the new 4 blade dual props?

Click to expand...


Not made for your setup. They are recommended for very high HP and heavy boats.

Check Mercury Racing for details.
 
".... wondering if switch to the recommended 20 pitch would cause any problems? "

No, it won't cause any problems & the 4" pitch drop sounds about right to attain top of the WOT spec. if same dia., cup, rake style, # blades ,etc of prop replaces the original.
Your engine will thank you for it, it will plane much faster and the prop slip and any cavitation will be diminished and engine load will be less at all previous rpms so it will be better able to maintain RPMs into big seas. More gear & POB's will affect it less. You ...might... even have a faster cruise at 75% or so of the the new higher WOT and at approx. the same NMPG as at the old slower cruise RPM .
 
RIght now I cruise at 3200 RPM and 28-29 MPH (GPS) and burn 12.5 GPH
 
BTDT. You should be cruising at ~3800 RPM's. On my Regal, I went from 3900 WOT to 5100 WOT with a prop change. My cruise went from 22 knots to 27 knots. My GPH went from 11 to 6. I suspect you will be very pleased with the change. The only downside is you may have to put more insulation in the engine room. Higher revving engines produce more noise.
 
3800 should be around the max cruise for that engine not necessarily ideal. Also agree that with the amount of fuel that engine is designed to push at full throttle, only achieving 4200 is a big deal. You have never really seen what that engine is capable of! I'm also surprised you did not go into an rpm limiting mode.

I think 4 inches is too much, but do whatever it takes to reach a solid 5K. These engines really love to breathe.

Personally I'd still target a more reasonable cruise of around 3400 rpm, kind of a sweet spot on the curve.

bp
 
I wish we had a good prop shop around here that would work with me on getting things right. I'd like to try this in steps.

My cruise now at 3200 feels good, but I want the pitch to be right.
 
Paul,

I have a set of 22's you can play with if you can't find a prop shop that will work with you there. Let me know as they are in the boat as a back up set. We’ll be going to the lake this weekend.

I really don't know if carrying around a back up set of B3's makes much sense as I think that if I strike something hard enough to screw them up, I'll probably have more damage than a prop change can help…..

Anyone ever use a spare set of B3 props after a strike to return to home port?

My e-mail and all are current...

Stan
 
Estimator, Stand by for an email. I just might take you up on that offer soon.
 
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