Questions regarding possible cavitation

[RXBoost]

I bought my 212x used last October. This is the first time I have really started messing with taking things apart and learning about the boat, mostly thanks to @buckbuck .

So I pulled out the pumps just to learn how to do it last night and noticed some very slight damage to the port side blades. Is what seems like slight wear, actually more than that?

Also, on the underside - 2 questions:

1. Is having that black plastic piece broken going to cause any problems?
2. Do I need to remove all the silicone and re-do it? The other side is actually worse.

Supposedly the previous owner only used the boat in a lake in Oklahoma - I dont know why the underside looks so nasty.... Is that a result of them beaching it all the time?

So in regards to the cavitation question - I have another thread asking about why I am not able to go even 10mph with the transom bag and stock bags filled up. If I go half capacity on the transom bag I can do just fine.

So I changed the plugs last night and went to the lake today - no change.

I dont REALLY know what cavitation is, I just wonder if it is happening (and is it because of anything in my pictures?) and that's why I am having so much trouble with the ballast being full and going nowhere.

 

[VitaminSea]

In the photo of your intake, are the “fins” parallel or is one twisted? Also, I would look at cleaning that tunnel. Any dirt will lead to friction, and could cause some cavitation.

Can’t comment to your impellers.

Not the official definition, but in my words...cavitation is when air get into the “jet stream”, and causes the system to operate less efficiently. The boats thrust is a result of moving as much water through the intake tunnel and out the jet. When air is introduced, there is a reduction in efficiency.

 

[RXBoost]

In the photo of your intake, are the “fins” parallel or is one twisted? Also, I would look at cleaning that tunnel. Any dirt will lead to friction, and could cause some cavitation.

Can’t comment to your impellers.

Not the official definition, but in my words...cavitation is when air get into the “jet stream”, and causes the system to operate less efficiently. The boats thrust is a result of moving as much water through the intake tunnel and out the jet. When air is introduced, there is a reduction in efficiency.

None of the fins appear twisted.

I am not sure how to clean that tunnel - I would love to - but that crap is on there good!

 

[VitaminSea]

1. Is having that black plastic piece broken going to cause any problems?

I didn’t see/notice what you were referring to here.

I am not sure how to clean that tunnel - I would love to - but that crap is on there good!

Have you tried a cleaner wax, or maybe a “hull wash” product?

Sorry I am not more of a help.

 

[RXBoost]

I didn’t see/notice what you were referring to here.



Have you tried a cleaner wax, or maybe a “hull wash” product?

Sorry I am not more of a help.

In the photo that shows the underside of the intake, there are 2 plastic 'bars' for lack of a better term - I assume to try to keep large things out - one of them is completely broken on one end (the left one in relation to the picture's orientation).

I havent tried a wax or a hull wash product. The dirt is actually protruding from the surface like sand.

 

[buckbuck]

@RXBoost
Those bars are the cast aluminum grate that you definitely want to change. I don't know if that would cause cavitation but feel it would disrupt the flow.
What kind of RPM are you getting at WOT?

I was hoping some of you guys would comment on the condition of the impellers. Is that 'burning' look evidence of cavitation? @Bruce, @Gym, @J-RAD, @Scottintexas, others?

 

[Scottintexas]

I would guess whatever broke that intake grate jammed in the impeller and made those marks, I'd check the impeller clearance gap and then pull impeller/shaft to clean the jet area with something attached to a drill

 

[RXBoost]

I would guess whatever broke that intake grate jammed in the impeller and made those marks, I'd check the impeller clearance gap and then pull impeller/shaft to clean the jet area with something attached to a drill

What do you mean 'impeller clearance gap'? I have pulled the pump/impeller out of the boat and there were no foreign objects.

 

[Scottintexas]

What do you mean 'impeller clearance gap'? I have pulled the pump/impeller out of the boat and there were no foreign objects.

see the instructions above for measuring the gap between the outside of the impeller blades and the wall,

I was thinking that whatever was able to break that intake grate tang may have bounced around on your impeller causing those marks,

we have seen pictures of air induced cavitation making "burn" marks on impellers also,

also, if you have all your ballast in the back it could make it difficult for you boat to plane out, we're you able to experiment with moving people of ballast forward to help the boat plane, I experienced this last time out, I would turn 10k rpm just trying to get to 10.5mph, once I had 3 people move to the bow I could plane out and go 10.5mph at only 8500 rpm.


.

Have you ever sucked anything up or ran anything over or did you inspect the intake grate when you bought the boat ??

 

[Scottintexas]

if you not comfortable with something let me know, maybe we can meet at ray Roberts or wherever, I'm no mechanic but I'm not afraid to take things apart!

 

[RXBoost]

View attachment 122904



see the instructions above for measuring the gap between the outside of the impeller blades and the wall,

I was thinking that whatever was able to break that intake grate tang may have bounced around on your impeller causing those marks,

we have seen pictures of air induced cavitation making "burn" marks on impellers also,

also, if you have all your ballast in the back it could make it difficult for you boat to plane out, we're you able to experiment with moving people of ballast forward to help the boat plane, I experienced this last time out, I would turn 10k rpm just trying to get to 10.5mph, once I had 3 people move to the bow I could plane out and go 10.5mph at only 8500 rpm.


.

Have you ever sucked anything up or ran anything over or did you inspect the intake grate when you bought the boat ??

Scott,

I haven't been able to mess with human ballast because it's always just my wife and myself going out and just moving her forward won't do anything.

I don't have a feeler gauge - I'll have to get one and take the measurements.

I suspect what you are saying will be the case for me as well - getting weight in the front will make a difference. I probably need to get a ballast bag to put up there, I'm just not sure where to put it as I would rather not put it on the floor and potentially in the way. I imagine I wouldn't be able to get much weight in the in-floor cooler area either.

I haven't run into anything since I have had the boat, and I never beach it either. I'm almost always in 40' water with the exception of the loading ramp.

I didn't realize you were in Corinth. We go to Ray Roberts whenever we go to the lake - the lake where we live is way too small and they don't allow ballast. I'd definitely be down for meeting up some time.

 

[Scottintexas]

I don't know how often your this way but I've got two spare 400# fat sacs sitting in my garage you could borrow,

I would bet just one on your bow floor would help a lot, it stinks having stuff all over but it's the price of surfing a Yamaha,

I would also consider do something with that broken tang
1. replacing the whole part (not sure if jet skis use the same part #, you could maybe cross reference at partspak or yamahasportsplaza) you might could find a used one online
2. taking it off and having someone weld it back or jb weld ( I don't know I'm just guessing, welding aluminum is different than steel)
3. cutting the tang completely off, you'd loose that protection but I don't think it's that needed


.

 

[RXBoost]

I don't know how often your this way but I've got two spare 400# fat sacs sitting in my garage you could borrow,

I would bet just one on your bow floor would help a lot, it stinks having stuff all over but it's the price of surfing a Yamaha,

I would also consider do something with that broken tang
1. replacing the whole part (not sure if jet skis use the same part #, you could maybe cross reference at partspak or yamahasportsplaza) you might could find a used one online
2. taking it off and having someone weld it back or jb weld ( I don't know I'm just guessing, welding aluminum is different than steel)
3. cutting the tang completely off, you'd loose that protection but I don't think it's that needed


.

Scott,

I will probably take you up on borrowing that fat sac. I happen to be in Lewisville this morning taking an exam off of fox Ave. You don't just happen to be home do you? I'm about to enter the exam so I won't respond for a little while now.

 

[Scottintexas]

sending you a private message (top right of the page) in a few minutes,

 

[Gym]

@RXBoost
Those bars are the cast aluminum grate that you definitely want to change. I don't know if that would cause cavitation but feel it would disrupt the flow.
What kind of RPM are you getting at WOT?

I was hoping some of you guys would comment on the condition of the impellers. Is that 'burning' look evidence of cavitation? @Bruce, @Gym, @J-RAD, @Scottintexas, others?

Thanks for the wakeup call @buckbuck. To be honest I can't determine from the pics whether that is cavitation ot sand abrasion. Does @RXBoost operate in the shallows very often?

 

[J-RAD]

I'd recommend fixing one thing at a time. The intake grate being the way it is could definitely cause cavitation. I don't see any signs of damage to the ware ring, just some extra abrasion on the impeller blade. Replace the grate and see what happens...

 

[RXBoost]

@Gym I operate in mostly 40'+ water other than when loading/unloading the boat.

@J-RAD what about just removing that one bar that is loose? Just since I really dont know anything about cavitation - why would the grate being the way that it is cause cavitation?

@Scottintexas Thanks for letting me borrow those Fatsacs, Im hopefully going to try one or both of them tomorrow evening!

 

[Gym]

@RXBoost. Cavitation is created when anything interrupts the smooth laminar flow of water through the pumps. When water doesn't flow smoothly air bubbles are created causing cavitation which causes lack of thrust. It's usually caused by foreign material stuck in the pump but can also be caused by loss of sealant or deformation of the intake grate.

 

[RXBoost]

@RXBoost. Cavitation is created when anything interrupts the smooth laminar flow of water through the pumps. When water doesn't flow smoothly air bubbles are created causing cavitation which causes lack of thrust. It's usually caused by foreign material stuck in the pump but can also be caused by loss of sealant or deformation of the intake grate.

Thanks for the explanation. So would you say that silicone being so poorly done/missing in places would be a potential cause?

 

[Scottintexas]

Definitely

https://jetboaters.net/threads/cavitation-missing-sealant-in-pump-grate.884/