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05 VLX with small vibrations, varies a bit with the prop. What is the list of things to check?


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2005 VLX with Monsoon 340 near sea level. 1520 hours, I have owned it for 500 of that. We wake, Surf, Zup, Tube about in that order. Large crew and little ballast for wake but 3500lb+ ballast for surf. I have 3 props with two mains. I have some varying issues (vibrations) with each and I want to troubleshoot and see if any maintenance is warranted. I list my props at the bottom.

My torque prop (acme 2419) has been rebuilt after running aground on a sandbar in about 14 inches of water. My speed prop (1939) has a small nick right now but very tiny. 2419 now vibrates throughout the range most of the time but sometimes it decides to be smooth for some RPMs. It didn't do this post rebuild and has not been injured since. When the vibrations began I switched to my speed prop and it's butter smooth except for when you really put the hammer down out of the hole, or accelerate from low speed pulling a bunch of tubes for instance. I am weirded out by the fact that the 1939 is smooth almost all the time though. I will rebuild both props this fall, but what should I look into first considering this is intermittent? I haven't replaced the prop strut/sleeve or ever aligned the driveline.

My thoughts would be:

  1. Needs new Strut sleeve/bearing or whatever it's called
  2. Driveshaft slightly bent after running aground.
  3. Props just need repair or rebuild, 1939 vibrating from cavitation, slip, or some small ding.
  4. Driveline Needs Alignment (which I haven't ever done and lines at the mechanic are long)
  5. ???

I can do a lot of DIY and happy to spend a few hundred troubleshooting instead of pulling it out and waiting for a dealer or mechanic.

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If anyone is interested the performance of these props for a 2005 VLX:

  • ACME 2419 15x12 - Freight train, but it runs high RPMs and wants to cruise at 22mph. 25+ gets more "revvy" than I want and so running for ice cream 3 miles away really sucks. Now that we surf less and board more I tend towards my 1939 just for grins. We have lots of guests and the kids love to "go fast".
  • OJ 14.5x14.25 - Very underwhelmed by this prop. It feels like a crappy compromise all around. I bought it super cheap and freshly repaired. Maybe the repair job went wrong but I just keep it around as a "spare spare"
  • ACME 1939 14x15.5Speed demon (GPS high 40s) and pretty good all round. I bought it as a pull off from a dealer when I ran aground on a sandbar in their lake. I took what they had just to get back on the water. Would never have chosen this on spec but it's my favorite prop now that we are surfing less. Only struggles with 4 tubes on it while getting the hammer down or really loaded up for wakeboarding.
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6 hours ago, 95echelon said:

When the vibrations began I switched to my speed prop and it's butter smooth except for when you really put the hammer down out of the hole, or accelerate from low speed pulling a bunch of tubes for instance.

My hunch is this is due to cavitation due to the higher pitch and high power settings.

 

6 hours ago, 95echelon said:

My thoughts would be:

  1. Needs new Strut sleeve/bearing or whatever it's called
  2. Driveshaft slightly bent after running aground.

Yes and yes.  Definitely worth checking both given it's basically free.

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It is more likely that the strut bent.  The shaft will follow the bend in the strut, but it is hard to get the shaft to take a set and stay bent.  The continuous flexing will work harden the shaft eventually, which could cause it to break.  The strut bushing will wear out quicker with a bent strut also.

Point the rudder straight ahead, then look from behind and in front of the boat.  The strut and shaft should be in line with the rudder and tracking fins.  If the strut curves to the side, it is bent.

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15 hours ago, formulaben said:

My hunch is this is due to cavitation due to the higher pitch and high power settings.

 

Yes and yes.  Definitely worth checking both given it's basically free.

I think you may be right on cavitation. I am asking a lot of that prop with 4 tubes on the back or 3-4 tons of weight to push while surfing. Shoot even teaching kids to Zup at WTW on Monday I could feel a small vibration with no ballast other than 5 kids and my wife.

I have cranked on the strut bearing and seems there is no (or very little) play. I am likely to replace just because of the age of all of this stuff. It doesn't seem unreasonable to do 200 bucks of potentially unneeded maintenance after 500 hours of fun.

Question: What is the best way to check for a bent shaft? I can buy a dial caliper, but I am unsure how to attach it. Some guys say "take it out and roll it" and that is fine but I thought I needed a special tool to remove it from the coupler (more $$$). It seems like there are a lot of specialized tools involved in all of this and it may be best to just pay the Stealership to do it. As someone who has self maintained my boats all of my life, it takes a lot to trust a shop to have the level of detail and concern that I have when going through things. However, they have done all this 100s of times and have the tool box to prove it as well.

2 hours ago, justgary said:

It is more likely that the strut bent.  The shaft will follow the bend in the strut, but it is hard to get the shaft to take a set and stay bent.  The continuous flexing will work harden the shaft eventually, which could cause it to break.  The strut bushing will wear out quicker with a bent strut also.

Point the rudder straight ahead, then look from behind and in front of the boat.  The strut and shaft should be in line with the rudder and tracking fins.  If the strut curves to the side, it is bent.

I was told by wakegirl when I first bought my boat that it was normal in those years to cant the rudder slightly to the side. This was supposedly to  help with counteracting prop rotation and also to allow for removing the driveshaft without removing the rudder. Mine seems to be like this. I'll try to nab some pictures tonight.

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My first order of business will be to align the coupler and then wet test. I looked into how to do this a lot last night and I feel it's straightforward. I have a nice set of gauges and various pry bars. The previous owner serviced the boat completely from a reputable dealer (AWS) and did everything recommended. Heck he even had the damper plate replaced (thank goodness). 

During covid my boat went from a cheap and cheerful 20-25k boat (but well maintained), to a 40-45k boat (per the dealer sales guy who came to WTW this week). It just makes me think I should be more proactive on Maintenance since the values are higher now. My buddy also just bought his first wakeboat - a 2003 23 XTi - and I can split the tool costs with him and take care of both.

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14 minutes ago, 95echelon said:

I was told by wakegirl when I first bought my boat that it was normal in those years to cant the rudder slightly to the side.

I'm not talking about the rudder.  I'm just saying you can use it to visualize a line between it and the fins.  If the strut is bent, no need to do an alignment until you fix that.  You can see mine in this photo.  The head and tail of the shaft tube in the strut are not in the same line as the rudder and fins.

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13 minutes ago, justgary said:

I'm not talking about the rudder.  I'm just saying you can use it to visualize a line between it and the fins.  If the strut is bent, no need to do an alignment until you fix that.  You can see mine in this photo.  The head and tail of the shaft tube in the strut are not in the same line as the rudder and fins.

 

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WOWZA, that's a bend. I'm assuming you replaced that.

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1 minute ago, 95echelon said:

WOWZA, that's a bend. I'm assuming you replaced that.

I straightened it on a press stand.  It wasn't that hard to do after I figured out how to set everything up to get the force where I needed it.  This is the type of bend you can get by running the prop into the dirt.

 

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1 hour ago, 95echelon said:

Question: What is the best way to check for a bent shaft?

A proper runout dial indicator should be used, but someone here once posted a picture of a coat hanger taped to the bottom of the hull to check for runout.  Yes, it's not super accurate, but if it bent a decent amount you'll definitely see some movement on the shaft. 

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1 minute ago, formulaben said:

A proper runout dial indicator should be used, but someone here once posted a picture of a coat hanger taped to the bottom of the hull to check for runout.  Yes, it's not super accurate, but if it bent a decent amount you'll definitely see some movement on the shaft. 

The wire method can be as accurate as you want it to be.  Any stiff wire will do.  Anchor it firmly somewhere (vise grip on the trailer, duct tape on the hull, etc.) and bend the free end so that it *almost* touches the shaft (perpendicular to the shaft).  Gently turn the shaft by hand and note whether the gap changes.  You should be able to test a shaft down to a few thousandths with this method by making the gap very small.  It might be good to test near the end of the shaft and again halfway from the hull to the strut.

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Follow up: It was the prop. Tossed my 2419 on there and it was butter smooth again. Tested driveshaft runout with the wire method and could not discern anything out of whack there. Just going to have my 1939 redone and then check alignment when I swap it.

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