Things That Cause Cavitation and How to Avoid Them

[djtech2k]

I know this is a discussed subject here but I have a different question/thought about it.

I have a 2012 210SX that I bought in the fall and had it in the water like 3x. I noticed that the port engine RPM's would shoot up if I hit the throttle aggressively and after posting here, I learned it was cavitation. I read a lot here and asked a lot of questions trying to resolve it. In the end, I ended up driving it 2 hours to a recommended boat mechanic at a nearby lake. He took the pump out and told me that I needed a wear ring and a prop. He said that the prop was "burnt" from running it with the cavitation. Its going to end up costing in excess of $1200.

Now I am worried that the other engine is going to do the same or even worse. So my question/topic here is how can you avoid the things that cause this kind of issue? I mean I understand that something can get stuck in the prop and affect the gap between the prop and the wear ring, which I guess causes cavitation. How do you avoid something like that? I mean water has debris in it. There is no way to avoid it. The mechanic said that if you feel cavitation, you should stop running that engine immediately and not use it again until its resolved, otherwise cavitation will cause all sorts of issues/expenses.

So for me, I am worried that it will happen on my 2nd engine or even happen again in the one I just had fixed. What can you do to avoid this? How often is this expected to happen on a jet boat (cavitation, wear ring/prop replacement, etc)? My boat has about 150 hours on it total. So its not like it has a ton of hours for a 2012.

Any ideas/experience you guys have with preventing, detection, protecting, and so on, let me know. At this point I am worried about these engines/jets getting messed up all the time or having to stop running it while out on the water or whatever.

The mechanic did tell me to run the boat and that I did not have to baby it or anything. He only looked at the port engine that he fixed so he did not comment on the starboard. He also said that docking the boat and pulling it on the trailer would be MUCH easier after these repairs. He said it will drive like a new boat in those situations now. I did buy the Cobrajet fins but planned to install them myself to save $$ because low speed steering was so difficult before. Now I wonder if I even need them since he said it will steer so much better. Oh well, I guess its just another $400 and time to install them lol. #BoatLIfe

 

[Matt Phillips]

With a used boat, it's hard to tell what may have happened with it's past owner. they may have run it with something in the tunnel on that side to cause this issue.

Basically anything that disrupt the flow of water up into the tunnels and to the impellers can cause cavitation. Probably the most common is something wound around the drive shaft in front of the impeller (weeds, lines, fishing line, etc). The other thing to do when the boat is on the trailer is get down and inspect the debris grates on the bottom of the boat: Are they smooth or have any dings that could disrupt the water flow? Check where the grates meet the hull...sometimes the silicone comes loose in that area and can cause issues. Make sure and check both sides.

Another thing that can cause cavitation is if the impeller itself is all marred up and out of balance.

Those are what I'd say are the largest and most common issues to be aware of.

 

[sunbyrned]

I collect debris usually at slow or idle speeds, so I’ve learned to just never idle. For example, after leaving the doc and I want to pull my bumpers in, I just turn the engines off. Also (although this isn’t preventative), when going slow and I hear or feel that I’ve sucked something in, I immediately try to spit it back out by throwing it in reverse. Others have different strategies. Doing these two things have made my boating days less frustrating.

 

[djtech2k]

So is cavitation something that happens because of debris or something like that or does it happen because of come kind of wear and tear? I mean I do not know how you avoid debris in the water as it will always be there. In my case, the mechanic said mine was wear ring and prop, so I'd like to avoid that in the future if there is anything I can do.

Just trying to get a handle on when this is more likely to happen and how to avoid it.

 

[Julian]

I know this is a discussed subject here but I have a different question/thought about it.

I have a 2012 210SX that I bought in the fall and had it in the water like 3x. I noticed that the port engine RPM's would shoot up if I hit the throttle aggressively and after posting here, I learned it was cavitation. I read a lot here and asked a lot of questions trying to resolve it. In the end, I ended up driving it 2 hours to a recommended boat mechanic at a nearby lake. He took the pump out and told me that I needed a wear ring and a prop. He said that the prop was "burnt" from running it with the cavitation. Its going to end up costing in excess of $1200.

Now I am worried that the other engine is going to do the same or even worse. So my question/topic here is how can you avoid the things that cause this kind of issue? I mean I understand that something can get stuck in the prop and affect the gap between the prop and the wear ring, which I guess causes cavitation. How do you avoid something like that? I mean water has debris in it. There is no way to avoid it. The mechanic said that if you feel cavitation, you should stop running that engine immediately and not use it again until its resolved, otherwise cavitation will cause all sorts of issues/expenses.

So for me, I am worried that it will happen on my 2nd engine or even happen again in the one I just had fixed. What can you do to avoid this? How often is this expected to happen on a jet boat (cavitation, wear ring/prop replacement, etc)? My boat has about 150 hours on it total. So its not like it has a ton of hours for a 2012.

Any ideas/experience you guys have with preventing, detection, protecting, and so on, let me know. At this point I am worried about these engines/jets getting messed up all the time or having to stop running it while out on the water or whatever.

The mechanic did tell me to run the boat and that I did not have to baby it or anything. He only looked at the port engine that he fixed so he did not comment on the starboard. He also said that docking the boat and pulling it on the trailer would be MUCH easier after these repairs. He said it will drive like a new boat in those situations now. I did buy the Cobrajet fins but planned to install them myself to save $$ because low speed steering was so difficult before. Now I wonder if I even need them since he said it will steer so much better. Oh well, I guess its just another $400 and time to install them lol. #BoatLIfe

Interesting question, and one that it never occurred to me that someone might not recognize what cavitation is - but dumb of me to assume everyone would know. If you buy a used boat that is damaged in some way and cavitating routinely you wouldn't know what the boat SHOULD sound like.

During one of the bimini trips I rescued a boat that ran out of gas - it was cavitating badly (which is why it ran out of gas). The owner didn't know what cavitation was. He had weeds wrapped around the shafts - and one of his clean out ports was stuck in place, while the other was very hard to remove and replace. Clearing the weeds eliminated the cavitation issue. Learn the reverse clean out maneuver.

Cavitation Described
Thread with a photo of impellers with Cavitation damage

Here is an impeller with cavitation damage:


Ways to avoid cavitation:

1. ensure your intake is smooth, no missing caulk and no growth/damage
2. Make sure you clear any debris in the pump
3. Make sure if you damage an impeller you keep an ear out to ensure it hasn't introduced cavitation

Most important is to listen for it and know it when you hear it. It is hard to describe, but its like the props are slipping....reving high with little/less thrust.

 

[djtech2k]

That's great info, thanks.

In my case, I noticed the "slipping" where the RPM's would go up and then fall back down. The intake area on mine does not looks smooth but I cannot fit my hand inside the grates that far. Around the outside of the grates I had put silicone before I took it to the mechanic.



The mechanic said it needed wear ring and prop because it was run with cavitation. Well I did run it 2 times or so after I noticed it because I did not think it was that bad or know what it was at the time. The mechanic told me to immediately stop running if I feel that again because it will make it much worse and cost more to fix.

Now that I am learning/hearing all of this, of course I worry about the other engine and/or this issue repeating itself. With all the talk of debris causing it, it makes me wonder how you keep this from happening all the time. So my reason for this thread was to discuss the reality of how often this kind of things is expected to happen and if there is anything that can be done to avoid. I will certainly pay attention to how the boat feels and sounds but not sure how to avoid the issue or what to do about it if I think its there. I have read the post about using reverse to try and clear it out and I will try it.

 

[TheShreve]

Out for the first time over the weekend and I notice my new to me SX195 has what I would call a slipping issue?? I did not notice any performance issues or top end (was only able to get to 40 due to conditions on the water). From idle to around 5 mph and then hard acceleration it feel like a slipping transmission. If i ease into it and let it plane I fell nothing and it is smooth and seems to accelerate normally, to me anyway. It is a 2017 with 48 hours on it. Should I be looking for damage or wear or both? TIA ..