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Topic: Gas motor mount for the AI  (Read 13095 times)

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lucky13

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Thanks. I'll keep an eye on that on.


LapuLapu

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Great work Ernie!  You have good design skills! 


lucky13

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Rey! Are the yellowtails biting yet?


lucky13

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I would like to update this thread to show the design changes I ended up making. My original design was rock solid. However, it sits too low and the motor had a problem with cavitation when going full throttle. In fact, I could only go half throttle. Any higher would cause cavitation.

So my second design was to elevate the motor mount by adding another piece of 1.5"x4" block to raise the motor. This works fine and got rid of the cavitation issue.



The second design was fine, but it began to feel a little heavy. A new design was desired to reduce weight. Here's what a came up with. I switched from the 1.5"x4" to 1.5"x3" aluminum tube with no lost of rigidity. All the green parts were 3D printed with a rubber-like TPU material. All the black parts that latch on to the Scotty mounts were 3D printed with PLA material.











And here's a video showing how I install and remove the mount and the motor.


Thanks for watching.
ernest
« Last Edit: October 05, 2021, 10:48:43 AM by lucky13 »


E Kayaker

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Nice job. Why is the cavitation caused by the motor being too low? I have a similar mount for an electric trolling motor. If I push it to full throttle it seems to suck air and jump and slam. What does your do? It seems to run fine at below 75% or so although it rocks back and forth as though the motor is surging. I assumed my high speed problem was caused by the motor being too close to the surface.
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NowhereMan

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Outstanding!

I use a couple of those orange knobs to mount a continuous furler on my DIY mini-bowsprit (for a spinnaker on my AI). Those things work great. Your 3d printed things are really impressive.
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lucky13

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Ken, I wish I understand it more to be able to explain what's going on. It doesn't make sense to me. I tried a bunch of stuff and finally noticed that most people mount their motor a bit higher than mine, so I tried it and the problem went away.
When I had the cavitation problem, if I give it 75% throttle, the kayak would not propel. It's like putting the motor in neutral and then gas it. I checked everything and no part of the mount was moving. I thought my motor popped out of gear at high speed or something. Took apart the lower unit and everything was solid, which made me check the motor height. Glad I was able to resolve the problem by raising the mount a few inches. With the raised mount, the motor's factory cavitation plate is only an inch below the surface. I thought it might cause ventilation (suck in air) problem but it didn't.

One of the things that can cause your motor rocking back and forth at high speed may be due to flex in your mount. If not, you can try to adjust the depth of the motor. Have you tried adjusting it?
"If I push it to full throttle it seems to suck air and jump and slam." This sounds like your motor is angled incorrectly. The direction of thrust should be parallel with the surface.
My electric trolling motor is situated right below the bottom of my kayak. I have no problem with it at any speed, but my electric motor has only 24lb thrust.

ernest


FishingAddict

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Very impressive  :smt006. Excellent building skills.
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Bushy

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Great craft my man.  Just a suggestion, but maybe install a vinyl coated braided wire leash from boat to the motor.  if things go all murphy on you, at least you can retrieve the motor....

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NowhereMan

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... maybe install a vinyl coated braided wire leash from boat to the motor. 

Word!
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lucky13

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Just a suggestion, but maybe install a vinyl coated braided wire leash from boat to the motor.
Roger that.

And thanks for the kind words everyone. Unfortunately, the latest design was not stiff enough. Oscillation became very noticeable when throttle above 50%. Back to the drawing board.


NowhereMan

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Unfortunately, the latest design was not stiff enough. Oscillation became very noticeable when throttle above 50%. Back to the drawing board.

Bummer, but I'm sure you'll soon work out the bugs.
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nudling

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Looks pretty!

From the 2nd pic in your latest post, if you're able extend the lowest red screw handle and increase the surface area, it'll prevent the rotation and use the bottom of the rear deck as a stationary point. The other points that you can use is the rod holders to prevent the oscillation.

I think I've spent 1000s of hours w/my motor on the AI and just kept adding stainless steel screws after the first trial in order to make it bullet proof. Still going strong for about 5 years but hasn't been used recently.

GL and keep us posted.
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lucky13

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Just want to provide an update. I made a version 2 of my motor mount which I just posted on YouTube. The new version does not flex under load.



tehpenguins

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Wow that looks Beefy!

super cool, I love seeing these at Rockaway when salmon come in.
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