What Should I Try
 

Wondered if the prop gurus might be able to offer me some insight as to what else i can try. Running a 31 Cig Bullet notched transom, bravos bout 650 hp per side. currently running 30p bravo1's and they seem to work ok. i am turning them in. at 4000rpm i am at 60-62mph and have seen 85 top speed. here is the issue, at 65+ in calm water the boat wants to porpoise unless i tab it down and then i scrub the speed. 85 was seen in calm water but it was trimmed wayyy up and turning 5500rpm.. my impression from this is that the boat w/ those props likes alot of trim but is there a better option out there? should i lab these to carry the bow better or try a different type prop?? Thanks for any insight

Re: What Should I Try
 

Your slip is a little high. It is lessening as the speed increases. This is good. Do you know where your prop shaft centerline is in relationship to the keel?

The prop can be worked to help decrease slip and help with the porpoise. However, it mat not completely fix the issue. We like that prop on your boat as the best all around performer.

Boat bottom, drive height,and CG can also contribute to the overall slip and attitude of the boat.

Re: What Should I Try
 

I could use a few more details Bulletproof. Do you have Dyno sheets on your motors? When you are trimmed for speed what is your WOT RPM and speed via GPS? What is your gear Ratio? It sounds as if your boat is not carrying itself consistantly. The Bravo I propellers typically are a good choice for the Bullets.

Julie

Re: What Should I Try
 

I ran 28s turrning in...similar power & speeds {1.5} ratio. Tried turning in once & I hated the way the boat felt !.. Never had a porpoise problem But,
at speed i always ran the tabs level.allowed more trim without chinewalk or porpoise

Re: What Should I Try
 

Thanks for the input. I will make a measurement from drive to keel tomorrow to see where that is. As far as dyno on the motors, i dont have that but i know that 650 is pretty close from past engine builds. Ratio is 1.5 and 85mph was on gps at 5500 rpm and the trim was maxed out on the indicators w/ no tab at all. I have the bottom being blueprinted to see if there is a problem there as well and i am thinking that a little cup may help carry the bow better. BirdDog, what rotation did you prefer? I have tried both and prefer turning out. i noticed that turning in, the whole boat seemed to lift more than just the bow.

Re: What Should I Try
 

Yep...I HATED them turning in.Like you said, It lifted the whole boat..

Re: What Should I Try
 

I have calculated 16% with the Bravo I 30P propellers. I would really like to see you around 10-12%. If you trim the drive down a bit what happens ...do you loose a lot of speed? The measurement from drive to keel may be of help. Or if you could post a picture we can take a look. Additionally would you say that your propeller has much cup in it? Is your 30P Bravo I Stock or Lab Finished? This could make a difference as well.

Julie

Re: What Should I Try
 

team skull ) I have an 88 31 bullet bravos what year is yours. I have been trying to dial this boat in for months bought this boat from the midwest boys. now in palm beach area of florida. boat has 509 merlins 600hp per. runs 73 5200 on gps 26 bravo1 props out . i hear these numbers you guys are reaching what am i missing. any help would be appreciated

Re: What Should I Try
 

Team skull...Mine was an 89. It had 871 blowers & cams to make big torgue. I could run a bigger prop & had the power to turn it. With N/A 600
If the mid-range isnt there you might not.with 28s it had unreal midrange.
with 30s it kinda fell on it's face. With labbed 30s it did everything well.
All Bravo 1s....

Re: What Should I Try
 

Thanks birddog for the reply . My bullet out of the hole is powerful mid range is very strong. according to my engine guys laptop dyno 2000 my peak torque is at 5000 586tq 596hp at5500 torque drops 569 hp takes over to 611hp. at 3000 my hp is300 my torque523 .was your torque much higher.