HELP!! prop for a 28 scarab with a blown 525sc????
 

Hey my buddy just got his 28 scarab that had a 454 in it and he has now just put a 525sc motor with a teague superchiller and blower on it running 7lbs of boost and has a bravoI drive with 1.36 ratio in it. He currently had a 4 blade 20pitch prop but theres no way that'll work now. and suggestions will help I'm thinking a 3 blade 24 or 25? possibly a 5 blade?? thanks!

i have a 24baja 540dart with 622 hp 136bravo drive i was runnig a 23mirage prop at 5600rpm runnig over 80mph. i just had the motor redone bigger cam and head work i am going to try a 25mirage prop .they work the best for me . i try 4blades do not like them on my boat hope that help you

Ok thanks for the input.

anyone else have anything close to this setup??

I have a 28' scarab with a 540 making around 645hp. It has an XR outdrive with a 1:50 ratio. I am currently running a labbed 28 Bravo and getting about 80 out of it. I know your ratio is different but the boat and power is similar. You can do the math and figure about what prop would work best for you with the 1:36 outdrive. Hope this helps some. p.s. with that power be careful with that Bravo.

Only one thing to do...........bolt on what you can and get a base line. Post that, we will have the answers to do exactly what is needed. Let's not guess. Let us know if you want to test any of our propellers.

Brett

I would start with a 24 or 26 Bravo 1. Those should be about 72-80mph props with proper slip and a 1.36 at 5200rpms.

I have a similar set up in mine.
28 Active Thunder with a 502, dart heads, cam and Procharger @ 7#
XR with 1.5 ratio Max 5 blade 28P untouched
The boat so far runs 87 GPS.
The ratio is the factor for your set up. It will require a special set up.

My buddy tried my 26p 4 blade bravo prop and said at full throttle it was at 3100 rpms? He put his 20p 4 blade prop bak on and ran 5100 rpms at around 60mph? Something isn't making sense. Can anyone help?

are you useing a gps for speed???????the other thing i would use is 3blade prop . wt is your red line on that motor if it 5200?i try 21mirage .now if its 5400rpm i try a 19mirage . with i 136 drive you have to you a small prop . like i said i run a 23mirage at 5600rpm and i am runnig over 80mph all the time i ran a 21mirage at 77mph i ran a 24pitch only got 4900 rpm 72 to 75 tops no good .i put that 23on my rpm went to 5600 and the motor runs the best . so the only thing i can tell you is look what your red line is on your motor prop it at that rpm and use a gps for your speed if that dont work then you got maybe fuel promblem ??

Red line is 6000 on the motor.

try a 19 pitch mirage not a plus .and what about your speed are you useing a gps or reg speedo?????

He's using his gps on his iphone he dont have a gps speedo and the speedo in boat. A buddy of mine seems to think a 23p 3blade bravo or something along those lines.

if you are runnig a20pitch 4 blade thats the same as a 21pitch 3blade so you will trun 5100to 5200rps with that 21. 1 pitch is 200rpm to 300rpm depening on the make of prop so if you go to a 19 you will trun 5500rpm . if you put a 23 your rpm will 4700.now you going the wrong way with your rpm .. . go with the smaller prop you will see more speed your rpms have to be higher !!!! so the motor is in its power band .. if you had 150 gears in your drive you would be puting bigger prop on like the other guys but you have 136 you have to use a smaller prop . i had a 454 with 450hp i was runnig a 150drive with a 25pitch mirage i switch to a 136drive i had to go down to 21 plus pitch doing 66.5mph then i put a 540dart now i am runnig a 23pitch and runnig over 80mph . i hope this help you out ??? good luck

Again, if you need to obtain some test propellers, let us know and we can offer some asistance.

Brett

6000rpms????????? Why???

If its just a 525SC with a chiller and pulley upgrade, then max rpm should be about 5300rpms. The stock rev limiter comes in at 5350rpms.

Something really does not make sense. How much HP was his last engine and what rpm/speed did it spin at???

I had almost the same engine in my 28 Pantera, just no chiller, but I had a roller cam. With a 1.5 drive I could spin a 26 Bravo prop to 5300rpms. With a 1.36 that would equal a 22-23 pitch prop.

I'm not sure why the red line is 6000 bu that's what he told me. The guy ho installed the motor art te timing at 8degrees when he installed I for my buddy. My buddy has now talked to the guy who sold him he motor said it should be at 34 degrees total timing at 4500rpms. Sound right??

Brett my buddy ben tried to get in touch with you several times and brad was suppost to get you to call him back. If you can call him anytime he needs to get with you about a prop. Ben 770)294-8072

Please try us tomorrow.
I just spoke to Brad and he was waiating for more performance information from you.......per your last connversation with him.

Let us know what you found out.

Brett

Does anyone know more info on these motors? As far as what the timing should be? What rpm range it should be at?(my buddy was told by the guy who sold it to him thAt the rev limit was 6000. He's hitting 5200 with the 4 blade 20p at 58-60 mph sounds right to me but just needs to change to a 3 blade not a 4 blade. Any help is greatly appreciated.

525sci's were rated at 4800-5200 with a 5400 rev limiter.

The boat is currently running 60 mph with 20" pitch propeller at 5200 with 1.36:1 gears. This comes out to 17.14% slip.

Even with a gear change and the correct propeller, the boat will only run a mile or two faster with the engine in the current condition.

Brett