Wonderful Cavitation Issue

[Kalock]

Well I knew it would finally happen someday. My 08 SX230 has developed one hell of a cavitation issue on the starboard jet (Why do people seem to always have issues on the SB engine????) Needless to say a whole day was ruined by an engine that feels like its getting zero bits into the water even at red line. I didn't want to pull the plug while out on the lake so I limped home on the port engine with the SB in no wake (It was a no wake zone anyways so it wasn't a big deal).

I'm heading over to the marina now to troubleshoot. Can anyone make sure I've got the basics down? I've been doing a LOT of research but a double check never hurts...

1. Check the intake for anything obvious or otherwise. Check seals on intake (I have no idea honestly what a good silicone seal will look like here)
2. Open the cleanout and look for stuff to pull out. Check plug for good seal (This is one I am worried about)
3. Look through gate and see if there's anything visible
4. Pull the pump and check the impeller, shaft, and bearings
5. Reseal the pump with fresh RTV while putting back together

Any other bright ideas?

 

[Scottintexas]

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

The attached is a link about my problems with pictures of the missing silicone, if it looks good also gently pull on it to make sure it's stuck and not on loose,

Don't worry to much about a good seal on the cleanout plug, your problems probably aren't there,
resealing really is only if you take the grate or intake off, if you just pull the pump you don't have to reseal,
there is a link in the FAQ about pulling the pumps that has a video also,

it stinks it ruined your day but at this point I'm not to worried your problem won't be easily solved,

 

[Kalock]

Yea I saw your thread while researching. It's a main reason I'm checking the silicone. Honestly my thoughts on the cleanout plug are just based on teh feel. It "feels" like there's very little water and a LOT of air going into the pump. To the level that I'm wondering if it would even be possible to get that much air when the boat is below planing speeds and the intake is deep in the water. What I'm feeling is of course assumption. It's just odd that at 10K RPM I'm doing 6MPH (This was only done to see if there was something in the tube to blow out using the forward, reverse, forward). My other concern is that the splines have stripped and I've just got a shaft getting no bite.

Reason says it will be something simple.

 

[dan144k]

Did you try the reverse move to remove debris in the impeller area. River by me is very high with a lot of debris. We were out yesterday and had more cavitation issues then usual. Most of the time it cleared itself out.

 

[txav8r]

No need to feel you can't pull the clean out plug on the water...that is why you have them! My guess is that you picked up a piece of driftwood or similar. It may be hard to see, but get used to looking in the intakes and in the rear of the pumps, as well as pulling the plugs. loose silicone can cause it, but some little piece of trash can easily cause it.

 

[Port0222]

Is there a reason you did not want to remove the plugs in the lake? That is what they are there for. Could be as simple as you sucked up a plastic bag to weeds to any number of your issues stated above. I personally would have started with taking out the plugs and checking for any debri.

 

[Scottintexas]

Do you have any unusual sound or vibrations or do you just hear the motor revving up? I didn't think about your shaft coming loose at this point of the process but usually with cavitation comes noise and vibration,

 

[Kalock]

Thanks for the help folks. Pretty sure the issue was a piece of rope that had been sucked in. Got under and gave it a huge tug and its out. I'm still going to pull the pump to see how things look.

As for the plug. The thing has a tendency to not want to go back in when there's any pressure in the jet channel which water causes. On land it's a phenomenal effort to get it in. I've never gotten it to seat in the water. So rather than chance having a dead engine while trolling back in I left it alone. as it is I couldn't get enough leverage on land to pull it out via the clean out port. I had to go in through the intake for a straighter line. I certainly wouldn't have wanted to do that on the lake. It was rough and someone else would be writing this

Thanks for all the suggestions. I won't know for sure it's fixed until I drop the boat back in but I'm feeling confident.

PS. The reverse then forward move didn't clear it on the water.

 

[Kalock]

And can I say WOW. This forum is so much better than The other one was.

 

[Bruce]

As for the plug. The thing has a tendency to not want to go back in when there's any pressure in the jet channel which water causes. On land it's a phenomenal effort to get it in.

Sounds like you need to rebuild the clean out plugs. $80 and 20 minutes will make your life much easier....
https://jetboaters.net/threads/rebuilding-yamaha-jet-boat-clean-out-plugs.46/

 

[Kalock]

I ordered a couple kits. I couldn't even get the plug to seat again. Will be a bit more forceful with it tomorrow to use the boat while I'm waiting.

The sucky thing is my dealer told be a rebuild kit doesn't exist. But they offered me a new manhole cover for the low low price of $279.

 

[GTBRMC]

The sucky thing is my dealer told be a rebuild kit doesn't exist. But they offered me a new manhole cover for the low low price of $279.

I frequently wonder if many of Yamaha's jetboat dealers are badly misinformed or crooks - it could be either. It is a problem for Yamaha, either way.

RU taking note, Ma Yamaha?

 

[Kalock]

Our local dealer here in Seattle is a "White Diamond Dealer". The sales folks know enough to get the boats out the door. It's when something deeper happens that it goes to poop. I asked what the plastic covered hole in the firewall was for just after getting my boat and was told it was for a subwoofer. Now I have a subwoofer there only to find out I've made getting to my computer connections VERY fun.

The parts department is relatively clueless about anything that's not got two wheels and a modified fart can...

 

[davel501]

I would not pull apart the pump for a piece of rope. Feel around the impeller and forward to the intake grate with your fingers through the cleanout to make sure it is clear and call it good. The pumps don't always come apart easily. Better to be boating than doing work you probably do not need.

 

[Kalock]

Yea I opted out. I felt up the impeller through the channel and from the outlet. There are some minor dings but nothing to warrant it yet. I'll pull both apart in October and put in new bearings and impellers. That may sound extreme but I'm planning two to three more years on this boat before getting a new 242

 

[davel501]

Yea I opted out. I felt up the impeller through the channel and from the outlet. There are some minor dings but nothing to warrant it yet. I'll pull both apart in October and put in new bearings and impellers. That may sound extreme but I'm planning two to three more years on this boat before getting a new 242

I am actually planning the same on mine. My top speed is down to about 47mph so I figure it is time.

 

[Kalock]

Haha same symptoms . Then again on Lake Washington I rarely go above 30. There's enough chop it gets bone jarring.

 

[dan144k]

@Kalock
if you have the impeller out. Minor dings can straightened at home with a large crescent wrench (just open it slightly to slide over blade and bent) or they can be sanded with a file.

 

[Julian]

Sounds like you got plenty of help on this one....main problem...you need get the manhole repair kits (the ones that your dealer didn't know about....sigh!!!). Glad you feel this site is much more responsive....the people and technology are awesome!