Prop Selection
 

The boat is a 25 outlaw 7.4 mpi 310 hp Bravo 1 1.50 ratio. running a 21p mirage plus (Wot 4600-4700)
I am adding a procharger 5psi bringing the crankshaft hp from 340 to 500... I was told by procharger that the kit will not add any rpms I dont no if thats true or not, however I am looking find a good place to start prop wise. A procharger tech said that you would typicaly go up 4 sizes after adding a procharger and another company said No way go up two sizes. So at this point I have no idea what to do, should I wait until I install the procharger and run the 21p and see what I get for rpm then adjust or should I just start with a bigger prop? Does anyone have any ideas as to what I should run?
Thanks,
Derek

Try a 25 Mirage

We have a Hammer with a 454mag mpi and run a 25 mirage up to 4900rpm at 72mph, best conditions. Un labbed it did 70 at 4700rpm. What is your best speed stock?

3 people and a full tank 55-56 ......4600rpm

I would check the internals of that engine before putting a Procharger on it......also I would take anything a "tech" at Procharger says with a grain of salt....just saying...:coolcowboy:

My 25 Ol just last week with a carb 7.4 480 hp 64.1 gps still tuning the engine. With 25p Ballistic prop. Will try the B1 24p next week.

I understand what you are saying about the internals being cast and all but the procharger is getting bolted on next week and when the motor pop's which it will, the question is when???? At that point I will do a total repower.
I was told similar things about the procharger people so I figured I would to turn to the oso members for advice. Surely someone out there has the similar set up.

When they say it will not add RPM, they are referring to the operating RPM range. If you do not change the prop when you supercharge it, the engine will undoubtedly increase the RPM it reaches.

26p bravo 1. Maybe a 24. Good handling and will give u great acceleration. Call blades and rent one get a baseline.

I agree, 25 mirage +. General rule, if you boat can get out of the water with a 3 blade it will be faster than a 4 blade 9 times out of 10.

The bravo 1 will handle better for sure.

Ok so I think its safe to say that everyone agrees that I should be running between a 24p and 26p. I would love to get the most topend but, im not sure its worth getting proped for topend because where I go boating I cant keep it wide open too long unless the conditions are perfect. Up here around cape cod we usually get heavy surff. On average how much speed do you loose going from a 3 blade to a 4 blade? And a 4blade would be better for what......low end...mid range? And lastly after the procharger installation should I be running a solid hub?

Our Hammer is 2mph slower with the Bravo 1. The Mirage + is more stable on top end but does not stay hooked up in tight corners like the Bravo 1. They have the same slip numbers all the way through the rpm range. Both are labbed.

How do you know which prop to run if you do not how how many rpms you will turn the current prop with your power adder? A lot of theory but IMO I would buy a prop after I upgraded and get some information from what you have now. I had a problem as well selecting the right prop but went with the theoretical propeller guides online after gathering my data and backing it up with recommendations posted in the forum thereafter...

Jctexas07...Sounds logical, But I was just looking to save time and see if any one out there had this setup so I could see what worked and didn't work for them. So far I have not bought or decided on a prop and the procharger is getting installed in a few day's. I might just wait and run the 21p that I have now and check the speed and rpm then bring the results back to the forum.

I have a Bravo One stamped as a 25P. PM me if your interested.

I know when I was selecting a prop, I wanted to make sure I was getting exactly what I needed. The numbers I got from my initial run with the advice here paid off bigtime. I researched and called and thought it through logically...if you are anything like I am, I wanted the first upgrade to be the right one. I will be excited to see what you get with your power upgrade.

ProCharger is in, took it for a test ride, needs minor tweeking.... still running the 21p mirage + getting 50.5 mph half throttle and hitting the rev limiter at 4650. How much should I go up on the prop?

what Rpms are you callings 1/2 throttle. I pushed my 21p m+ to 50 mph at arount 4100 rpms! How hard are you hitting rev? with drive still neutral or raised or even tucked??

I was hitting rev with my mag 385hp and moved up to 23p m+.. I would say 23p m+ and it will give you good indication whether 24p b1 or 22p b1

if hitting rev hard.. would go straight to 24p b1 or 25p m+

loaded, I can only push 24p to 4700

hope this helps based on my trials with 454 mag

Nailit,
I was at 4650rpm at half throttle with the drive in the neutral position and got the gps reading of 50.5. As soon as the rev limiter kicked in I pulled back on the stick. Before I added the procharger I could be at wot with the drive high enough to start seeing a rooster tail before I hit the rev limiter with a top speed of 56. My engine's operating range is 4200-4600rpm. On the factory gage im at 4650 when the limiter kicks in.

sounds like you have some juice in that thing! I would say the 26 b1 would be a good place to start! a 24 will not be enough so if the 26 is too much or not enough then you can lab either way up or down a little!