Prop Tests/Recommendations

Feel N Good

Cadet
Joined
Aug 5, 2009
Messages
8
1. 07 Ebbtide Extreme
2. boat length 20.10 w/ext platform 23.2 beam 8.6, weight 3475lbs
2a. 320 hp
3. 2 adults (combined wt 300 lbs) 1 child 45 lbs, avg 35 gallons
4. occasional tube, mostly riding wide open
5. Deep Vee 20 degree
6. 07 5.7GXI Volvo
7. 320 hp 1.51 gear
8. 5200 rpm
9. n/a
10. pad, hull has been true'd
11. n/a
12. Volvo 14.75 x 19 (prop shopped tweaked added a little cup) prior to hul being true'd
13. 5350 (on the rev limiter) 58.5 mph prop part # 3858027 (old part number for Volvo) tested the following props this week after hull being true'd
Mirage Plus 19P - 5000 rpm - 54 mph
Mirage Plus 21P - 4650 rpm - 53 mph
Prior to hull being true'd
Enertia 21P - 4900 rpm - 55 mph, (stuggled to lift boat)
14. sea level
15. good
16. two years, testing props for maximum speed and performance.
17. no
18
19. overall best performance at maximum speed.

I have had access to several mercury props through the local mercury dealer, so I tested a few and the results are posted above. I was just wondering what could I expect if I put a Rev 4 on there? Any results on similiar boats??
Which pitch to start with??? The dealer here doesn't have any I can test so if he orders it, it is mine.
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Prop Tests/Recommendations

Feel, thank you very much for supplying all of the information I need to do an analysis. I show part number 3858027 to be an OMC Stainless Steel prop with a 14 3/4 x 19" pitch, please verify this is either right or wrong. When I did a normal analysis without considering you had a pad bottom on this hull I found you should be able to get about 51 MPH, but when I considered the boat is more like a bass boat with a pad bottom I was able to obtain your speeds.
The Revolution 4 is a superb 4 blade SS prop, but it is designed to run very high in the water column and that is where it is at it's best, and on a stern drive it will not be running at its best, in my opinion. The OMC SS 19" prop you are running now, in my opinion, if you have them add another theoretical 1 1/2" pitch by cupping the prop to drop another 300 RPM I think would be your best bet.
Please run the boat with the original 19" pitch SS and see what the speed is now that you have the bottom blueprinted, and lets see how that prop does now.

Prop Slip

FeelNGoodPropSlip.jpg



H
 

Feel N Good

Cadet
Joined
Aug 5, 2009
Messages
8
Re: Prop Tests/Recommendations

HWSII,
Thank you, That is correct on the prop (verified) by OMC/BRP. All the results I posted were after the bottom was blueprinted, with exception of the Enertia which was done prior to blueprinting. After blueprinting I picked up 300RPM's with the OMC prop. The OMC prop was worked on to increase bite while cornering prior to me testing. Sorry I did not mention that earlier.
I agree, the OMC prop is about as good as it is going to get.
I'm just curious to what a 4 blade would do, not neccesarily REV 4.
If I ever get a chance to test a 4 blade, I'll let you know.
What would be the difference if I had a 21P in the same prop since we are adding 1 1/2 of pitch and the current prop has bite added to it??? I need another prop as a spare anyways.
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Prop Tests/Recommendations

Anything that I would say would be of no use without knowing what they actually changed on the prop and how much they changed it and where they made the changes to the prop. Normally they just cup the trailing edge to lower the RPM and to help decrease prop slip and add theoretical pitch, but there are other things they can do as well. If you can find out from the prop shop exactly what they did to the prop and how many RPM it lost after their changes I would have a better guess, but it would still be a guess, because one persons light cup is another one's heavy cup, and they actually could have cupped the blade tips and not the trailing edge, which would have added more bow lift and theoretical pitch, instead of stern lift and theoretical pitch.



H
 

Feel N Good

Cadet
Joined
Aug 5, 2009
Messages
8
Re: Prop Tests/Recommendations

I really appreciate the slip graph. Prop guy here keeps good records of every prop he touches. I'll find out over the next few days just for our info. Thanks again.
 
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