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GoFastRacer
HDF Supporter
V-Driver For Life!
    
Big River, Ca
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Spectra20
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Posted: July 20 2010,5:45 am |
Post # 2 |
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Sounds like it's an old prop?????, ears will flex especially aluminum. Did this started right after the last repair or just lately???, if it started right after the repair it's possible they decreased the size a bit repairing it instead of building it up, you would never see it but it's noticeable when used. If it just started lately odds are it's getting tired and should be replaced???...
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| Member # 101 | Joined: 3-03-2003 | |
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WATERDOG
Gemini
HDF Silver Supporter
Don't Bother Me, I'm in Havi
MENIFEE, CA
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ELIMINATOR EAGLE
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Posted: July 20 2010,4:20 pm |
Post # 6 |
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| Quote (Hockey Family @ July 20 2010,3:02 pm) | I don't know what ratio I'm running. Think I have that written down at home somewhere.
The numbers I gave in the first post may not be exact. I typically run a few high RPMs to MPH.
I believe at about 60 hrs of use, Â I hit WOT at about 5300 or 5400 RPM at about 49/50 MPH.
Now that I think of it, Â it has seemed like I've been running a little higher RPM with less MPH lately. |
Assuming you have a 1:50, At 5350 rpm @ 49.5 mph, you're still at 23%. This along with your 24% at 3500 tells me that the prop has "flexed" to somthing less than a 19 pitch. With even a 10% slippage, your prop is now a 16 pitch. The Prop is history. I run a SS Mirage, 19 pitch, your welcome to try it in Havi if you want.
BTW, if your running 1.38 gears, your slippage will be much worse. Numbers should be printed on your drive.
Edited by WATERDOG on July 20 2010,4:22 pm
"Damn you sure know how to fock things up."-GFR
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GoFastRacer
HDF Supporter
V-Driver For Life!
Big River, Ca
Posts: 62,729
APPD 7.90
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Spectra20
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Posted: July 21 2010,6:13 am |
Post # 8 |
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| Quote (Hockey Family @ July 20 2010,4:02 pm) | I don't know what ratio I'm running. Think I have that written down at home somewhere.
The numbers I gave in the first post may not be exact. I typically run a few high RPMs to MPH.
I believe at about 60 hrs of use, Â I hit WOT at about 5300 or 5400 RPM at about 49/50 MPH.
Now that I think of it, Â it has seemed like I've been running a little higher RPM with less MPH lately. |
I'd say it's definitely getting tired, best to replace it before an ear brakes off, that plays hell on the equipment, an SS is the way to go!.. 
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WATERDOG
Gemini
HDF Silver Supporter
Don't Bother Me, I'm in Havi
MENIFEE, CA
Posts: 10,292
APPD 1.60
Post Rank: 8
ELIMINATOR EAGLE
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Posted: July 21 2010,12:27 pm |
Post # 12 |
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| Quote (Hockey Family @ July 21 2010,11:48 am) | | Quote (WATERDOG @ July 21 2010,11:21 am) | | Quote (Hockey Family @ July 21 2010,10:42 am) | Thanks all...
I didn't know prop fins get weak over time. That's what it seemed to me, but I wanted to hear from other "knowledgeable" boaters that this could be the case. Wasn't sure if it might be something else.
I did switch it out to my backup prop, which only has a few hours use on it. So that should be good for now until I can afford a SS.
I'm still a little worried about going with SS because I tend to find shallow rocks when they're in the area. Â 
All the numbers about pitch and rpms and ratios hurt my head. Anyway I found some info last night.
I run Volvo Penta 5.0L GXI SX and I'm pretty sure the gear ratio is 1.60:1
Not 100 % sure. The boat is in AZ so I can't look at the drive. |
Basic metal fatigue. Those props have 1000 of pounds of pressure on them and they get hot even in the water.
Rocks are a lot worse on alum than steel as alum is weaker and softer.
If the drive is a 1.6, that would knock your slip to 18%, that's still high. |
As far as Rocks and SS.... my concern is the impact on the drive.
Doesn't the weaker alum take away from the force that would be put on the drive gears?
I know hubs are also designed to be sacraficed in a strong impact.
Mostly I'm thinking of low speed hits.
Should I worry about the impact on the drive? |
Both the Alum and SS blades have same rubber hub to help with the impacts. Alum would absorb more as it is softer but I don't think your hitting rocks as hard as you might think or your prop would be bent big time already. Just an idea, wouldn't be better to stay away from rocks.
"Damn you sure know how to fock things up."-GFR
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11-23-2024 Not boat related (Rep.#41) from: GoFastRacer
