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30 Spectre 300x O/B very slow to plane

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Old 09-28-2017, 04:36 PM
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Default 30 Spectre 300x O/B very slow to plane

I recently purchased some 32" Bravo 4 blades which have been worked for an outboard application. The issue I have is that when I try to get on plane, it takes a really long time. I can push the throttles all the way down and the RPM's wont climb over 2500 or so. After 10-15 seconds the props will start to slip, motors will rev up to 5000 RPM and the boat jumps up on plane. Once on plane the props seem to perform well. Good top speed, cruise speed, less hop than the 3 blade cleavers had. The props have the PVS holes completely open. I have tried positive trim, neutral and negative trim. Seems like negative trim is the best option but it still takes a long time to get on plane. Has anyone else experienced this issue? I really dont feel like it's an issue with the motors since they both do the same thing. When I switch back to the cleavers with exhaust over the hubs the boat planes quickly.
Any advise would be appreciated.
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Old 09-28-2017, 06:50 PM
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I recently purchased some 32" Bravo 4 blades which have been worked for an outboard application. The issue I have is that when I try to get on plane, it takes a really long time. I can push the throttles all the way down and the RPM's wont climb over 2500 or so. After 10-15 seconds the props will start to slip, motors will rev up to 5000 RPM and the boat jumps up on plane. Once on plane the props seem to perform well. Good top speed, cruise speed, less hop than the 3 blade cleavers had. The props have the PVS holes completely open. I have tried positive trim, neutral and negative trim. Seems like negative trim is the best option but it still takes a long time to get on plane. Has anyone else experienced this issue? I really dont feel like it's an issue with the motors since they both do the same thing. When I switch back to the cleavers with exhaust over the hubs the boat planes quickly.
Any advise would be appreciated.
I'm running box stock 32 Bravo 1's on a 28 Skater with 300 XS's I have 1 3/8 vent holes in my hubs. On the hit, the motors pull kinda lazy (15/20 feet) then break loose and boat leaves pretty good (motors go to 5000 rpm)
You could try drilling a second set of holes next to the PVS holes (probably same size, doubling the vent area)
The other fix is some high dollar 5 blade, over hub props.
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Old 09-28-2017, 07:54 PM
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I'm running box stock 32 Bravo 1's on a 28 Skater with 300 XS's I have 1 3/8 vent holes in my hubs. On the hit, the motors pull kinda lazy (15/20 feet) then break loose and boat leaves pretty good (motors go to 5000 rpm)
You could try drilling a second set of holes next to the PVS holes (probably same size, doubling the vent area)
The other fix is some high dollar 5 blade, over hub props.
I would drill second holes one at a time until you see what it likes.
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Old 09-30-2017, 09:29 AM
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Default prop vents

This is Mercury's answer on their newest outboard props

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Old 09-30-2017, 10:33 AM
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I think that is what I am going to have done. I'm a little disappointed since I was told that the props I was buying would work great on my application, and they do aside from getting on plane. I was just curious if others had experienced the same issue.
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Old 09-30-2017, 04:26 PM
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I think that is what I am going to have done. I'm a little disappointed since I was told that the props I was buying would work great on my application, and they do aside from getting on plane. I was just curious if others had experienced the same issue.
The Bravo's have such a large ear that they are hard to break loose. More or bigger holes will help, but there will still be a little lag time, then they will snap loose. The over hub props will come loose earlier and seem smoother, but probably will not maintain the cruise speed you're getting with the Bravo's unless you step up to higher $$ props.
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Old 10-02-2017, 07:26 AM
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I will try adding more holes and report back. I appreciate all the help!
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Old 10-02-2017, 07:49 AM
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so they need exhaust to cause slip so they can over-rev (at least for the current speed) to get going. kinda like a nascar racer. you let clutch out without smoking tires, it is gonna bog and stall cuz gearing is so high.
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Old 10-03-2017, 11:48 AM
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If BBLADES did the work for you on these props, I believe you might have purchased Bravo OB/F's. This is a BBLADES design we often use on this exact set up with great success.
The vent holes we put into this prop is our 7/8" CAP system. They are larger than the Merc PVS system which is only 5/8". This is a additional 1" more venting on the OB/F than the standard PVS. That amount of venting is typically plenty or even too much.
However, each application can and is different. Whether we built the props or not we can open up the vent holes to 1.125" or put in a 2nd hole.

FYI. The photo above of the Bravo 1 FS is the same bravo 1 casting from forever. It simply has the exhaust tube and cups trimmed with 2 vent holes installed and a new marketing name. These are all modifications we have been doing to the Bravo family for 2 decades. Very similar to the OB/F we do with the Merc casting or our new BBLADES 4-SPEED OB/FX. But the 4-SPEED OB/FX has a true 15.25" diameter where the Mercury castings vary from 14 7/8" to 15" although advertised at 15.25".
I'm not discounting potential performance of the XS, FS or any of the other Bravo 1 "new" props, I am just explaining the prop is not new nor are the adjustments made to them. The only thing new is the suffixes.

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