Prop for 272 Baja Islander 502/500hp
 

I'm looking for a new prop for my repowered Islander, but also a bit of an education on prop setup as I'm new to the offshore scene.

The boat currently has the Bravo Mirage 23p that worked with the stock 454 Magnum that was not running when I purchased the boat. A 502/500hp motor is going in its place. From what I've seen on comparable boats is a Bravo 1 24p is a common choice for this setup. What are the advantages/disadvantages of a 3 blade prop to a 4 blade unit?

1996 Baja Islander w/Bravo 1 drive, weighs 4400lbs, and occasionally used as a tow boat for wake boards/tubes but a fair amount of open bay ocean as well.

Thanks in advance!

That weight is real dry I believe...

Yep, I got that from the factory spec sheet. They probably even wiped the dew off the boat before hitting the scales. ;)

Took it out this weekend with the new 502/502hp 23p Mirage Plus prop, and got 48mph on iPhone GPS at an indicated 4800rpm. Does that sound about right?

I need to check the carb linkage to make show the secondaries are opening completely as that seems a bit meek to me.

But one issue seemed to be the prop tends to suck a lot of air. Normal? Can that be tuned out?

Sounds like excessive slip to me.... I cruise at 50MPH @ 3,500rpm in my 26ZX Donzi with a 26P Bravo 1 prop...... My 502 is not stock but I would try a 24P Bravo 1 with your setup...... Make sure you are trimmed properly but it sure sounds like that prop is not working at all for you......

Yea, I thought of stepping up to a 24p as this is the stock prop on the 454mag that came out of the boat. I was surprised to see only 4800rpm on the tach, but as I was writing the previous post I remembered that this is a new setup and I better check that I'm getting full throttle.

Would a lower pitch prop tend to slip more? It blows out on any turn sharper than 50 yards regardless of the trim position.

you are getting very high slip around 31% you should be around 15%. I am surprised that your rpms were not higher, or even hitting the limiter it you had one. I dont know your speed before but you should conservatively add 6mph with the 500hp. i would try a 4 blade 26P bravo 1, it will hook up alot better.

Wow - 31%!

I did check the throttle throw and the secondaries are opening, and it has a Holley red fuel pump at 67gph at 5psi or 97gph free flow so that should be enough.

I was expecting to jump up to at least a 24 or 25p. It's weird that it won't swing a 23p beyond an indicated 4800.

rev limiter set low? tach not showing true reading? how did it run with the 454? speed, rpm? any other changes to boat?

I never ran the boat with the 454 as it came from the previous owner with a limping 496 truck motor. No rev limiter that I know of on the HEI ignition. The gauges do act kinda funny as if the dash panel isn't grounded well as the some of the switches "pop" through the stereo system, and if I turn the blower switch on it turns off the stereo all together so I know that I have to straighten out some of the previous monkey's work. What is the best way to verify the tach is working correctly? I don't mean to turn this tread into a troubleshoot thread as I do have one already going here.

What does 31% slip indicate? Not enough pitch?

31% slip indicates a bad prop or prop breaking loose and not hooking up.

http://pages.suddenlink.net/kmielen/C320Docs/Tach.htm
http://www.amazon.com/Digital-Laser-.../dp/B007KGHD3O

Im sure there are more ways, i just did a quick search.

That method of checking the tach is pretty interesting. Thanks, Sabo, for your legwork and help.

Spoke with Brad at BBlades, and he's hooking me up with a Revolution4 21p after I play with some tuning this weekend. I'll let you know how it all works out.

21p? seems like going the wrong direction in pitch, but hopefully motor runs good and you can get some decent numbers to go off, good luck!
My predictions are if motor running good, you'll hit 60 at max rpm.

21p does seem backwards, but it is a 4 blade vs the current 3 blade. I'd be totally stoked with 60mph. From what I've seen on the internets these open bows tend to lose ~5 mph compared to the cuddly cabin bretheren.

Open bow! didn't realize that, but with the right prop i think you should still run around 65 with 500hp...

just keep in mind, weight makes a big difference, so if you have a full load with 4 people and 3/4 tank fuel your going to run slower

So I put a dial indicator on the prop blades, and with the first blade set to zero the next blade was .03 out and the next was .05 out. Is this significant?

http://i622.photobucket.com/albums/t...8064663108.jpg

http://i622.photobucket.com/albums/t...67E171B70E.jpg

Prop looks decent to me, i don't think this measurement is relative to the issue, but im no prop expert.

My 272 ran 62 stock with a 23 mirage plus at 5050 or so *, would hit 63-64 completely empty no fuel, no passengers empty banging rev limiter (502 mag)

Thanks for the input! Cuddy or open bow?

Yea, I'm getting almost 32% prop slip for some reason. 50mph @ 5k with the same B1 Mirage Plus 23p.

Its a cuddy cabin boat but there isnt that much difference. I tried a 23 pitch hydro once that banged rev limiter at 53-55mph too, try a diff prop so you can see wtf is going on, Smitty

I chimed in on your other thread. These numbers (MPH, RPM, slip) are all over the place/don't make sense and need to be baselined. But that prop must have issues. Is it a solid hub? M+ 23 slips/blows out bad in stock configuration, but 31% is insane. I will also step out on a limb and say you DONT want a 21 pitch wheel behind 500HP in your 272. I'm running 20 MPH faster than you with similar power.

Smitty has more seat time testing everything possible in a 272 than the rest of us combined. When he's typing, I'd pay attention. Good Luck.

Exactly, Hook'em. This mirage keeps blowing out, so I can't trim up enough to get things up and loose. Looking at the prop I can see scuff marks where it hit some mud, and feeling the lips of the blades one feels straight, one feels slightly cupped in the outside half inch, and the last blade even more so. After feeling the bends I can see them now. Maybe it's enough to cavitate the prop to where I can't trim up without it blowing out. That's the current theory. A 23p 4 blade dhod be right on the money if not small.

This may not be the issue, but i see you have a long pickup tube for the drive shower and the bolt and nut hanging down in the water steam. I would trim tube to around 1/2-3/4" below cav plate and flip and counter sink the bolt. this may help keep some aeration out of the prop.

Yep, the prop needs attention ASAP. That IS the right prop for the boat when tuned properly. Is yours a solid hub?

Good eye Sabo. I didn't even notice that pick up. Thats a problem Rooster, actually that could be lots of the problem with reguard to cavitation.

Will do, and good call. Baja Dan called that out in my other thread as well, but I figured that it's not a big deal being after the prop and such.

*Copy/pasted from my other thread in Baja*

So...tested the new prop over the weekend.

23p 4 blade Revolution 4.
~60g of fuel on board.
Fresh drive fluid
Drive shower trimmed up
3 adults and an ice chest
Bimini top folded up on the front windshield
Huge tube tied to the back sun deck
80* weather on a slightly choppy lake

Top speed squeezed out was 54mph at an indicated 4800rpm
No blowout to speak of!


The new prop felt great - nice shot out of the hole, handles way better, much more responsive to speed adjustments, and even docked/loaded up easier as well. It achieved the 50 mph mark much much easier than it did with the M+. I was pretty stoked with the performance of the prop, but was hoping for just a bit more top speed. ;)

It looks like that may be all this boat has got. The motor is an Eagle 502, so that should be a reliable part of the equation. I had a few toys on board, from the reviews that I've seen have shown this boat to go 60-65mph with the stock 454. I otherwise love the boat.