DuoProp Align / Clocking
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DuoProp Align / Clocking
Hi Everyone,
I have a DuoProp on my 220 and just saw a mention online about aligning or clocking the props. Had never given this any thought but I did notice last year that after painting the outdrive and changing the drive oil that my top speed was down about 5 MPH. Obviously new oil and fresh paint wouldnt cause the lower speeds and the only other "change" was the props were removed and replaced without any regard to orientation. After looking at some pictures when I purchased the boat, I noticed the props were set in an alignment that could create a water Flow or maybe better bite.
Below is a picture.
I did some searching here and other sources and there wasnt a consensus for either the DuoProp or Bravo to align in any manner for better performance. VP or Merc didnt have any recommendations per the other sources about aligning though some did mention several times about blades meeting at the cavitation plate.
My initial thought was relating this to aerodynamics on a race car and managing air flow, though in that case you are trying to move or direct air to create downforce while lowering drag. Hydrodynamics would need to work with similar principles to grab/direct the water while also limiting drag. The action of water shear, flow, drag and air bubbles entering the equation would need to be managed in some manner, so I figured would at least start a winter conversation.
I have a DuoProp on my 220 and just saw a mention online about aligning or clocking the props. Had never given this any thought but I did notice last year that after painting the outdrive and changing the drive oil that my top speed was down about 5 MPH. Obviously new oil and fresh paint wouldnt cause the lower speeds and the only other "change" was the props were removed and replaced without any regard to orientation. After looking at some pictures when I purchased the boat, I noticed the props were set in an alignment that could create a water Flow or maybe better bite.
Below is a picture.
I did some searching here and other sources and there wasnt a consensus for either the DuoProp or Bravo to align in any manner for better performance. VP or Merc didnt have any recommendations per the other sources about aligning though some did mention several times about blades meeting at the cavitation plate.
My initial thought was relating this to aerodynamics on a race car and managing air flow, though in that case you are trying to move or direct air to create downforce while lowering drag. Hydrodynamics would need to work with similar principles to grab/direct the water while also limiting drag. The action of water shear, flow, drag and air bubbles entering the equation would need to be managed in some manner, so I figured would at least start a winter conversation.
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- jhnmdahl
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Re: DuoProp Align / Clocking
I've heard of clocking so that the blades aren't at 12:00 at the same time, but I've never heard of anyone observing a difference with a Volvo Penta outdrive. I guess some older Mercury Bravo 3 outdrives could have more cavitation if they weren't clocked, but I've only heard anecdotal rumors of such things happening. I clocked mine anyway, despite not believing it really makes any difference.
Administrator of the www.cobaltchat.com Cobalt boats community forum
2015 210 (Volvo Penta 5.7L V8-225)
2015 210 (Volvo Penta 5.7L V8-225)
Re: DuoProp Align / Clocking
I also have heard of this, but never any real world experience. I have had Bravo III's and now a VP Duoprop. My props get removed every year for service, sometimes by me, other times by the dealer. If they get "clocked" it's by accident and I have never noticed anything abnormal. But, there is no downside to doing it, so might as well align them if you think about it when installing.
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2014 Cobalt R5 - Current
1999 SeaRay 185 Bowrider -Previous
2000 SeaRay 290 SunDancer - Previous
1979 Correct Craft Ski-Tique - Previous
1948 Chris Craft Custom Runabout - Oh man to have that one back!
Re: DuoProp Align / Clocking
I used to try to clock my props on my Volvo and then one time I forgot....there was no difference that I observed.
BTW, you try to clock them so that the props aren't at 12:00. What that really means is anyone's guess. Does it mean both blades at 12:00 or just the trailing edges at 12:00.
BTW, you try to clock them so that the props aren't at 12:00. What that really means is anyone's guess. Does it mean both blades at 12:00 or just the trailing edges at 12:00.
2017 R5 350HP Mercruiser Bravo III
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
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Re: DuoProp Align / Clocking
I would tell you mine look like this....on my old merc and current volvo, not 100% but this is what I pictured.
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Re: DuoProp Align / Clocking
On my R5 with a Mercruiser, It has a rear 4 blade...pretty much impossible to clock that.
2017 R5 350HP Mercruiser Bravo III
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
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Re: DuoProp Align / Clocking
Maybe a silly question, but wouldn't they all look like the pic above if you rotate the counter rotating props and just stop when they line up??
2003 Cobalt 293
Twin 5.0 GXi Volvo Penta 270 Hp
With Volvo DPSM Drives
Southern Lake Huron
Twin 5.0 GXi Volvo Penta 270 Hp
With Volvo DPSM Drives
Southern Lake Huron
Re: DuoProp Align / Clocking
The theory is, you don't want them to line up at 12:00.Jimmy Buoy wrote: ↑Fri Jan 05, 2024 6:15 pm Maybe a silly question, but wouldn't they all look like the pic above if you rotate the counter rotating props and just stop when they line up??
2017 R5 350HP Mercruiser Bravo III
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
Northridge, CA
Big Bear Lake, CA
South Lake Tahoe, CA
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Re: DuoProp Align / Clocking
Ok. I think I get it. Will play with mine come spring and see at what hr they do line up!bruceb58 wrote: ↑Sat Jan 06, 2024 12:53 amThe theory is, you don't want them to line up at 12:00.Jimmy Buoy wrote: ↑Fri Jan 05, 2024 6:15 pm Maybe a silly question, but wouldn't they all look like the pic above if you rotate the counter rotating props and just stop when they line up??
2003 Cobalt 293
Twin 5.0 GXi Volvo Penta 270 Hp
With Volvo DPSM Drives
Southern Lake Huron
Twin 5.0 GXi Volvo Penta 270 Hp
With Volvo DPSM Drives
Southern Lake Huron
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Re: DuoProp Align / Clocking
Thanks for all of the feedback. I know most of us have already put away their Cobalt's in storage so no way to get real world data until things warm up quite a bit, especially here in the Northeast. A little boat talk, even if limited, is always a good thing to keep us engaged until the first spring startup video from BBP and the burbly Bib Block.
I will be conducting some back to back tests to give my results come spring.
I will be conducting some back to back tests to give my results come spring.
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Re: DuoProp Align / Clocking
I actually made a quick video on this subject at the end of last season.
In the end, I do not believe it is required or necessary for a VP drive. But see no reason not to do it when you put your props back on.
Just one more week till I fetch the boat from storage......
In the end, I do not believe it is required or necessary for a VP drive. But see no reason not to do it when you put your props back on.
Just one more week till I fetch the boat from storage......
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