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Just had Port engine begin Cavitation

rkluck

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We were running along nicely on this beautiful afternoon when all of a sudden the port engine started cavitation. We didn't hit anything or see anything, just running along about 30 MPH around 6K RPM. The port side would start the cavitation around 3300. I just brought the boat back to the dock and will look at her next weekend. I plan to get the boat out of the water and check the plug (pain in the ass) and see if I can tell what happened. I figure if I have her out then if I need to anything else I don't have to fight to get the plug back in. Hopefully I can get her back running pretty easily next weekend. This is just so very odd, must have sucked something up!
 

Bruce

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You very likely have something, perhaps a twig, piece of algae or plastic stuck in the jet. This is a common experience early in the year on the lake I live on.

Why is it difficult to remove the clean out plugs? If they are swollen you can rebuild them easily and cheaply with this part Rebuilding Yamaha Jet Boat Clean Out Plugs. It costs about $35 a plug and I believe requires removing and installing 8 screws. It is an easy job. After rebuilding Yamaha suggests removing the plugs after every outing.

#StuckPlugs
 

Big Shasta

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Definitely remove your cleanout plugs after every outing. Mine were swollen when I got the boat but they go in and out easily now that I remove them every time. Imagine you had sucked something up that prevented the engines from running at all, like a fishing net maybe (I know, dual engines disabled isn't real likely, but...). You would want access to those cleanout ports on the water.
 

Ronnie

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I've had a piece of wood the size of a pencil's eraser head cause cavitation like you described and it didn't just fall out after I turned off the engine since it floated in the intake instead. It may fall out once you get the boat on the trailer though.

Fishing line will also cause cavitation and if you have any in the pump or on the impeller shaft you are sure to find it still there. Having working cleanouts comes in handy in both situations.

If neither of these things or something similar is causing your cavitation try looking for missing silicone where the pump and hull meet. Some people have said that their boats don't have any such silicone but having had two yamaha jet boats since 2008 I can say that both pumps in both of my boats had silicone at these locations an on one occasion I had to reinstall it to eliminate cavitation in that pump. I suspect that the silicone either wore out after years of use or that debris damaged it.

Good luck finding and solving the source of your cavitation. It doesn't sound like it is going to be hard or expensive to fix. Regardless, $70 to $80 to refurbish your plugs is an inexpensive way to better assure that they work when you need them to so I highly recommend restoring the plugs if you haven't done so yet. I leave my plugs in most of the time, except when I store the boat in the off season, but I just accept the idea that I will have to refurb them every 2 to 3 years.
 

rkluck

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I may need to silicone. I know I saw some small sections missing before. Is there a recommended type? I may get the rebuild kit. I don't ever need to take the plugs out and since whenever I did (even when new and taking them out every time) it was such a pain to out and back in I stopped doing that. I knew eventually I would have to do this! :) I just need to get my tools and see what I can figure out next weekend. The boat is up at the lake house. I will get it out of the water first just in case there is an issue with plug.
 

Bruce

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I don't ever need to take the plugs out and since whenever I did (even when new and taking them out every time) it was such a pain to out and back in I stopped doing that.
After rebuilding the plugs should be easy to install and remove. When I bought my SX230 I had to use two pieces of 2x4 as a lever with a strap to pull the plugs. I placed a short one on the clean out port cover to spread the load then placed a 3' to 4' 2x4 on top with a strap attached between the 2x4 and clean out plug. Then lifted the other end of the longer 2x4 using it as a lever to pull the stuck plug. I hammered the plug back in with the 2x4 to reinstall. I had to do this for a month or so until I could get rebuild kits which were backordered at the time.
 

rkluck

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Thanks for the feedback. I will see if I can get the rebuild kit this week. Any recommendations on the silicon type for around the grates?
 

Bruce

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Any recommendations on the silicon type for around the grates?
I would pull the plugs, clean out whatever is likely stuck in there and rebuild both long before thinking about recaulking the jets which is a much more difficult process.
 

Ronnie

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@rkluck , I agree with Bruce. That is see if its a plug problem before considering rechalk . If you do need to rechalk I recommend either 3m 4200 or life chalk. Regular rtv silicone failed on me a week or so sfter I installed it and 3m 5200 is so strong it took me hours to remove and redo a single pump.
 

HidnNOS

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Ronnie knows what he is talking about. Re'calk the pumps as a last resort. On the boat I bought from Ronnie we had this issue. It made NO SENSE to me one side had edges and yet Ronnie wanted to calk the other like crazy. I let him do what he felt right and years later I'm enjoying the hell out of the boat cavitation free! Thanks again @Ronnie
 

rkluck

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Thanks for all the feedback. I will pick up the plug re-builds (just in case) and silicon Friday from the dealer. I plan to get the boat out and give it a good visual first and then get the plug out. Hopefully I will be able to see what is going on.
 

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If it happened that quickly my bet is that you have something in the pump, even some weeds will cause that to happen.
I have sucked up sun glasses, a cast net someone threw in the water under a bridge, toys , plastic bags just about anything imaginable even a dead fish during a red tide outbreak.
 

rkluck

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You have been able to clear those items out through the plug hole?
 

Cobra Jet Steering LLC

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First you need to see it, in some cases you have to look up from underneath the boat inside the intake grate using a good flashlight, other times you can locate the item through the clean out plug. On my skies I have to remove the intake grate if the item is stuck. Since they do not have a clean out plug. However cavitation is usually caused by some trash in the pump .
 

rkluck

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Well the weather finally gave me a break and I got the boat out so I can check this out. I hope to be able to give an update next weekend.
 

rkluck

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I got the plug out without much trouble (maybe because it is a little cool). I did not see anything along shaft. I went under the boat and looked up into the grate and on the port side I see some scratches where the impeller blades are but I did not see anything that is caught up. I looked at the other side and the housing did not have any scratches. I couldn't turn the shaft so I use the engines. I had to get the water out anyway. I marked the blade on the top and even though the impeller turned it always stopped at the same position every time (about 5 runs). I looked at it as the impeller turned but I couldn't see anything, not a big surprise. Looks of noise but both sides were exactly the same. So I am confused now. Maybe there is something small under the one blade I can't see. I tried to run my hands around them but I can't reach all the way around. I also didn't feel anything where I could reach. So either the problem was pushed out when loading the boat or there is something else going on. I thought I may have to take the housing off to make sure but I am not sure there is anything caught in the impeller now. What else may cause this problem? If I need to take the housing off should I take the 4 inside bolts off or the 4 big bolts near the outside. I don't have my book with me today. Next weekend I will work on it more. I was hoping to get her running next weekend for the kids but that may not happen at this rate. I really thought I was going to find some rope or line wrapped up in there. Thanks in advance for any thoughts.
 

Ronnie

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There is a chance that whatever was in there simply fell out the last time you put the boat on the trailer. Did you take the boat back out again or just inspect and turn the engine over on the trailer?
 

Bruce

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I believe that it is more likely that whatever was causing your cavitation has fallen out than that you will find something by pulling the jet. I would put her back in the water and go for a test run before pulling the jet.
 

rkluck

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We had a lot of people over at the lake house so I did not take her out. I plan to be there next week and I will put her back in the water first and see how she runs. If there is still a problem does it make more sense to pull the grate or pull the pump? If the pump is the best choice which set of bolts should I remove the larger outside bolts or the smaller set on the back plate? I plan to see if I have any indication from the book but I know lots of you have done this before so any advice is helpful. Thanks!
 
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