Bravo3 Prop Pitch

[agallant80]

So I will admit it. I bought an underpowered boat. I currently have a Bravo3 outdrive. Will messing with the pitch help keep it on plain? That is my biggest complaint. Currently I have to be running at abou 3600 RPM to keep her on plain, it takes a long time to get on plain and she will fall off plain real easy. I understand how prop pitch works on an alpha but I have never considered how it works with two props and if pitch can help you stay on plain.

With that said I am not sure I have the right props on her. At WOT (the lever mashed to the firewall) she will over rev pretty easy.

EDIT:

I just want to give some more details. When the boat is stopped and I mash the throttle down she will struggle, the RPMs don't climb fast. Once she is crusing along on plain (say 3600 RPM) and I gun her the RPM can shoot over 5000 pretty easy.

Its a 2013 5.0 MPI

So what I am really wondering is it just as simple as the 260HP are not enough and just live with it or is there somthing that can be done with the prop pitch that will improve her. With that said I cruse about 3700-4000 RPM at around 24-27MPH

Also I just read something about timing the props? Does anyone know about that? Could they just have been put on wrong?

 

[anzomcik]

Re: Bravo3 Prop Pitch

I have little experience with the two prop outdrives, but Do you use your trim when getting on plane? Also do you have trim tabs? I assume this drive is on a bayliner 255cr?

 

[Fun Times]

Re: Bravo3 Prop Pitch

Also I just read something about timing the props? Does anyone know about that? Could they just have been put on wrong?

Are your propellers 4 X 3 blade or 3 X 3 blade? as they now offer both.

Have the part numbers and pitch size handy? Is there an (L) in the part number? L stands for cupped propeller.

There are lots of yes and no theories about timing bravo 3 props as it started with the black hawk surface-piercing drive as it's in the service manual to do so to help with cavitation burns on the propellers, better overall performance, less vibration, less water "splat, splat" type sounds hitting the cavitation plate where the main problem seems to lie, better handling, and the list goes on and on for hours when searching Timing Bravo 3 Props online.

I myself am in the yes it helps theory as I've seen it first hand and shown by our local Mercruiser propeller representative in our area that it works and should be done. Since then, I've been timing them for years with no complaints afterwards.

Also, what is your gear ratio?

And just to confirm, you are hitting the rev limiter right now at WOT?

 

[tpenfield]

Re: Bravo3 Prop Pitch

What you describe sounds fairly typical of a small block that has a fair amount of overall horsepower (the 5.0). So, at the top end it is sufficient for the boat, but in the low to mid-range it does not have enough torque to bring the boat up on plane quickly, etc.

Since you are hitting the top of the RPM range at WOT, you could not really go down in pitch to gain a better hole shot. So, maybe the thing to do is to go to a 4 x 3 or a 4 x 4 blade combo. More blades will tend to improve low-mid range performance. Although on a B3, it already has a pretty good 'bite' on the water. Stainless Steel Propellers, Boat Props, Marine Accessories | Hill Marine

The only problem, is that with the duo props, 'playing around' with blades and pitch is wicked expensive (especially if you get it wrong), so most folks don't really do much of it.

As far as timing the props . . . you can Google "bravo 3 propeller timing" and bring up some articles and forum posts on the subject. Supposedly, if the propellers are just put on in a random location on the shafts, relative to each other, the boat will loose top speed and RPM.

Of course, I neglected to do this last season, so I will have to be sure to do it this season.

 

[agallant80]

Re: Bravo3 Prop Pitch

Yes I am hitting the rev limmiter at WOT. The guardian system will start beeping, I have never pushed until the system lowers the RPM on its own but I can get it up to about 5100/5200RPM and it will start beeping. I never run it that fast anyways. I was under the impression that if the prop selection is proper than it will run in the WOT range with the throttle fully down.

tpenfield best described the issue. There is not enough low end power. Last summer I had 4 adults and 2 kids on the boat and it was a dog. It took forever to get on plain. I had the throttle all of the way down and the RPM was climbing so slow.

As for blades, pitch and gear ratio I will have to go look. I think I have 4 blads in the back and 3 in the front but I am not sure.

 

[Slip Away]

Re: Bravo3 Prop Pitch

In reality, you can do little with your boat to change it's ability to stay on plane without sacrificing some other performance. Basically, live with it.
Deploy more tabs at planning speed, back of the throttle, and you will be able to maintain plane at a slightly slower speed.
I have some engineer friends that work at the Fond du Lac plant, and I asked them about the timing of props, since I had twin BIII's on our 30ft. cruiser.
There exact words were " We get that question from time to time, and there is no truth to it"

 

[agallant80]

Re: Bravo3 Prop Pitch

There is a part of me that is waiting for the day the engine goes so I can replace it with a 5.7....... I guess that is why I don't worry too much about running her at 3800-4200RPM. When she goes its a great time to put in the 5.7 she should have been ordered with.

 

[agallant80]

Re: Bravo3 Prop Pitch

Perhaps adding a Bennett auto tab controller may help my stay on plain issue. I tend to lose interest in chasing the tabs.

 

[Slip Away]

Re: Bravo3 Prop Pitch

Perhaps adding a Bennett auto tab controller may help my stay on plain issue. I tend to lose interest in chasing the tabs.

Maybe. The Auto Tab Control is sort of like a Showtime Rotisserie "Set it and Forget it":lol:

 

[agallant80]

Re: Bravo3 Prop Pitch

Maybe. The Auto Tab Control is sort of like a Showtime Rotisserie "Set it and Forget it":lol:

Good old Ronco