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Old 08-14-2022, 08:34 AM   #1
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Nimble Vagabond Prop Cavitation Issue - Help please!

Good Morning,
We have owned this boat for a long time and only had it in the water once.
It didnít have a motor when we got it.
It now has a used 50 hp bigfoot Mercury on it.
The prop that was on it seems to cavitate and is not pushing it correctly. To much boiling etc.
Can anyone take look at the photos and offer suggestions on solving.
I have seen a youtube video of how this boat handles with a 50 honda on it and it does much better than what we have going on.
Thanks for suggestions.
Tammy
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Old 08-14-2022, 10:23 AM   #2
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IMHO the outboard is a bit too high. If you can lower it a few inches.......

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Old 08-14-2022, 11:06 AM   #3
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The cavitation plate should be below the boat bottom. Hold a strait piece of wood against the boat bottom and extend to the motor and take a picture to share. The motor could could be too high as suggested earlier. Also the prop hub rubber bushing could be slipping when under load. Try a different prop
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Old 08-14-2022, 11:25 AM   #4
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Tilt seems to be up too high. There should be an adjustment where you pull a long pin out and return it to a different set of holes.
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Old 08-14-2022, 01:27 PM   #5
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Run the prop through the Merc online prop calculator and compare what it says to what you have now.
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Old 08-14-2022, 02:52 PM   #6
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Thank you for your suggestions everyone.
We will take a look at all of them and see what we can figure out.
Tammy
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Old 08-14-2022, 02:53 PM   #7
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My understanding is that your boat is a displacement hull, not a planning hull. As a result, you have too much horsepower and too course a propeller. If you want to use that motor, a very flat pitched propeller will work much better. Flatter pitch means a lower pitch number. A pitch of 10" would be half the pitch if 20".

From what I've read on the internet, 10 horsepower would be enough to push it nicely. Over 20 horsepower is probably of little gain.

Ted
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Old 08-14-2022, 06:06 PM   #8
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What is the hull speed your trying to attain?
Is your hull a sail boat hull? In your second pic it appears to be.
Does your hull have a short 2x4 keel on it? If so does it hang down in front of the prop?
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Old 08-14-2022, 07:12 PM   #9
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That flat bottom planing hull should move very nicely with a 50 horse outboard. It is hard to judge from those pictures but is the motor tilted all the way down to the operating position? The way it sits right now it appears it is at the wrong angle when the boat would be in the water. Because of the angle it almost looks like the leg isnít quite long enough. Despite that, directly in front of the propeller is the square end of the small Keel. That blunt end of the keel makes very disturbed water approaching the propeller, that disturbed water will have air pockets that are being introduced to the propeller. The propeller needs smooth water flowing into it, otherwise it cavitates. Also the bent leading edges of the propeller arenít doing you any favours. As mentioned, too steep of a pitch might not get the boat moving forward fast enough before the power starts it just spinning (cavitation) instead of grabbing the water and screwing itís way through it.
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