Mirage vs Revolution 4 test results - thoughts?

[thunder550]

I have a demo 23" pitch Revolution 4 from bblades that I tested back-to-back with my original 23" pitch Mirage (plain Mirage, not Mirage Plus) yesterday. This is in a 1995 Cobalt 252 25' bowrider, 502 Mag, Bravo 1, 1.5 ratio. Both props are 23" pitch. Bblades is closed until Monday, planning to call and discuss results then but in the meantime I thought I'd get some input form the forum. I love the Rev4, it has a great hole shot, gets on plane quicker, seems more stable at tow sport speeds. The only question in my mind is whether I should keep the 23p demo unit or swap it for a 21p. I lost 400 RPM off the top end but still pulled the same top speed. This was with me alone in the boat, so running probably 400-500 pounds lighter than a typical trip with extra people, coolers, bags, etc.

[FONT=&quot]RPM - Trim - Mirage MPH - Rev4 MPH[/FONT]
[FONT=&quot]2000 - full down - 9 - 12[/FONT]
[FONT=&quot]2500 - full down - 22 - 26[/FONT]
[FONT=&quot]3000 - 1/2 - 32 - 35[/FONT]
[FONT=&quot]3500 - 1/2 - 38 - 42[/FONT]
[FONT=&quot]4000 - full up - 46 - 49[/FONT]
[FONT=&quot]4500 - full up - 51 - 56[/FONT]
[FONT=&quot]WOT - full up - 60@5150 - 60@4750[/FONT]


[FONT=&quot]Mercury prop slip calculator shows me at 20% slip with the Mirage and 13% slip with the Rev4 running wide open. [/FONT]With the Mirage, my previous best was 57mph at 4900 RPM, so running light gained 250 RPM and another 3mph. If those same results translate to the Rev4, my top speed loaded will be around 57mph at 4500 RPM, which is below the 4600-5000 max RPM range recommended for my year 502.

Thoughts?

 

[porscheguy]

I own a rev4and a mirage+ in 21P. In my case, I can hit redline with both. Ive also got a 23p mirage+. Both mirage+ props of mine have made a trip to the prop shop for extra cup.

As for the rev4, you can read about my experience with it in the thread I started titled 1990 wellcraft performance.

In your case, you should probably drop down to a 21p rev4. Props are more efficient as their rotating speed increases. In many instances the lower pitch can result in a higher top speed with reduced slip.

Another suggestion is to see if theres a prop repair place near you and send your mirage in for extra cup and refinishing. If youre happy with it as is, you can always search on Craigslist for a used mirage+. They turn up all the time.

 

[thunder550]

So going down in pitch usually results in less slip? I'm at 13% with the 23p Rev4. I'll check out your thread.

I pulled the 23" Rev4 off today to send back. The advice I've gotten on the few boards that I'm on has been unanimous to go to the 21". The load that we had on the boat yesterday was probably low/mid-range with 3 adults and 1 kid. Being on the bottom end of the WOT range with that load I definitely agree with going to 21".

 

[porscheguy]

Pitch has no bearing on slip. Its merely a factor used in calculating slip.

Slip is the difference between the theoretical performance of a given prop pitch, and the actual performance of the prop.

If you were to screw the prop (your 23p rev4 for example) into a solid material, it should move forward 23 inches for each 360 degrees of rotation. When the prop is on your boat and in the water you see the real time performance of the prop. Slip is the difference in percent between the theoretical and the reality.

Weight, cup, hull shape, x dimension, etc can all have an impact on slip.

 

[QBhoy]

Pitch has no bearing on slip. It’s merely a factor used in calculating slip.

Slip is the difference between the theoretical performance of a given prop pitch, and the actual performance of the prop.

If you were to screw the prop (your 23p rev4 for example) into a solid material, it should move forward 23 inches for each 360 degrees of rotation. When the prop is on your boat and in the water you see the real time performance of the prop. Slip is the difference in percent between the theoretical and the reality.

Weight, cup, hull shape, x dimension, etc can all have an impact on slip.

Hands down, The best abrieviated, to the point and right on the money explanation I?ve seen on this. Well done that man !

 

[thunder550]

Pitch has no bearing on slip. It?s merely a factor used in calculating slip.

Slip is the difference between the theoretical performance of a given prop pitch, and the actual performance of the prop.

If you were to screw the prop (your 23p rev4 for example) into a solid material, it should move forward 23 inches for each 360 degrees of rotation. When the prop is on your boat and in the water you see the real time performance of the prop. Slip is the difference in percent between the theoretical and the reality.

Weight, cup, hull shape, x dimension, etc can all have an impact on slip.

Thanks for the explanation, I understand the concept of slip, just looking to see if there's any correlation between pitch and slip. Sounds like it just depends. I shipped the 23" Rev4 back to bblades this morning and ordered a 21" from them. On backorder for now, probably end of December before it arrives. Guess it's back to the Mirage for now

 

[porscheguy]

If you like doing business with bblades see how much theyll charge to add some cup to your mirage or to bring it up to mirage+ specs. Youre overreving a bit with it now, but you probably wouldnt see any gains from upping pitch. If you add some cup to the mirage and bring it up to mirage+ specs you may be making enough power to keep your rpm the same and pick up some speed. I know youre more focused on the rev4 but I think the mirage is a good prop and potentially faster.

 

[thunder550]

I'll ask next time I talk to him. There's a prop shop here in Phoenix that can do it too, probably check with them as well.

I want to see how my numbers stack up from the Mirage to the 21" Rev4 before I do too much though.