In depth - Prop depth question? (punn intended)
10-03-2008, 07:06 AM
#22
Registered
5 blade props
Guys,
Just an FYI on the 5 blades I've run.
All the Hydromotive P5-Xs, regardless of pitch or modification level have been fast and stable.
All the Maximus I've run have been very efficient in the midrange, but due to their large diameter are hard to turn on top end and take some driving, because they are trying to twist the boat around.
The new Precision that I tried (a 30") showed very good midrange speed, and was also stable. Since my motor is tired, I really couldn't turn it (88 @ 5300), but It did show a lot of promise. A fresh motor and some minor tweaks would make this one work.
My conclusion is to take the P5-X out of the box and go to the lake.
Regards,
Steve
Just an FYI on the 5 blades I've run.
All the Hydromotive P5-Xs, regardless of pitch or modification level have been fast and stable.
All the Maximus I've run have been very efficient in the midrange, but due to their large diameter are hard to turn on top end and take some driving, because they are trying to twist the boat around.
The new Precision that I tried (a 30") showed very good midrange speed, and was also stable. Since my motor is tired, I really couldn't turn it (88 @ 5300), but It did show a lot of promise. A fresh motor and some minor tweaks would make this one work.
My conclusion is to take the P5-X out of the box and go to the lake.
Regards,
Steve
10-27-2008, 03:15 PM
#24
Chris
Gold MemberThread Starter
Re-post of response in prop slip thread:
I spent all day Friday and Saturday doing back to back prop testing. Things were facilitated by Tim of OCM. We tested props at 4.5" depth (1 inch spacer) and then re-tested with prop depth of 5" (1.5" spacer). I have always felt that my boat (an open bow) didn't carry the nose high enough. Testing has now confirmed this, as going to a 1.5" spacer brought my speed up between 1.5 and 2 mph across the board. I was afraid that lowering the outdrive would drop my rpm's because of more prop bite and outdrive drag. Instead, the outdrive lifted the boat up more, thus reducing boat drag more than the lowered outdrive increased drag. The result is that I gained aproximately 100rpm on top end while reducing slip. At this point, the bravo 28 and the 30 bravo are both running 81.5 mph +/-. The 28 is just kissing the rev limiter at 5400, and the 30 is a little lazy getting to full speed. The 27 P5x is also just barely hitting the rev limiter, but is about 1 mph down across the board. Prop slip on the 28 Bravo is the most efficient of the bunch at 11.6%. My boat now has a more "nose up attitude" running across the water, and just plain feels better! At this prop depth (5" from keel to propshaft centerline), the 4 blade props are beating out the 5 blade props in both cruise speed and top end. The increased outdrive depth, decreased slip on the 4 blade props, but did not really affect slip on the 5 blades. The exception to this was when I tried Tim's 29 pitch, 5 blade, round earred, Herring. This prop was a little too big for my horsepower, but exhibited 9.8% slip. My cruise speed at 3000 and 4000 rpm went up 7 mph effortlessly. Top speed was 79.5 mph at 4800 rpm. This prop was extremely smooth in every way but the pricetag. My summation of this test is that open bow boats probably need more outdrive depth than the closed bow boats, in order to better carry the bow.
Special thanks to Nordic and Tim of OCM for making this testing possible by supplying props, outdrive spacers, and time.
NORDIC ROCKS!!
I will continue testing,
Thanks,
Chris
P.S. Steve, My son inadvertantly left the 28P5x Labbed prop at home and I was really bummed. I will be testing this prop, the next chance I get.
--------------------------------------------------------------------------------
I spent all day Friday and Saturday doing back to back prop testing. Things were facilitated by Tim of OCM. We tested props at 4.5" depth (1 inch spacer) and then re-tested with prop depth of 5" (1.5" spacer). I have always felt that my boat (an open bow) didn't carry the nose high enough. Testing has now confirmed this, as going to a 1.5" spacer brought my speed up between 1.5 and 2 mph across the board. I was afraid that lowering the outdrive would drop my rpm's because of more prop bite and outdrive drag. Instead, the outdrive lifted the boat up more, thus reducing boat drag more than the lowered outdrive increased drag. The result is that I gained aproximately 100rpm on top end while reducing slip. At this point, the bravo 28 and the 30 bravo are both running 81.5 mph +/-. The 28 is just kissing the rev limiter at 5400, and the 30 is a little lazy getting to full speed. The 27 P5x is also just barely hitting the rev limiter, but is about 1 mph down across the board. Prop slip on the 28 Bravo is the most efficient of the bunch at 11.6%. My boat now has a more "nose up attitude" running across the water, and just plain feels better! At this prop depth (5" from keel to propshaft centerline), the 4 blade props are beating out the 5 blade props in both cruise speed and top end. The increased outdrive depth, decreased slip on the 4 blade props, but did not really affect slip on the 5 blades. The exception to this was when I tried Tim's 29 pitch, 5 blade, round earred, Herring. This prop was a little too big for my horsepower, but exhibited 9.8% slip. My cruise speed at 3000 and 4000 rpm went up 7 mph effortlessly. Top speed was 79.5 mph at 4800 rpm. This prop was extremely smooth in every way but the pricetag. My summation of this test is that open bow boats probably need more outdrive depth than the closed bow boats, in order to better carry the bow.
Special thanks to Nordic and Tim of OCM for making this testing possible by supplying props, outdrive spacers, and time.
NORDIC ROCKS!!
I will continue testing,
Thanks,
Chris
P.S. Steve, My son inadvertantly left the 28P5x Labbed prop at home and I was really bummed. I will be testing this prop, the next chance I get.
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