yamaha 242 Limited S 2014

[Tom Denion]

Hello all, about 5 months ago I posted a YouTube video of my boat cavitating really bad especially the port engine, I finally got my boat out of the water, if you search [img 0529] on utube you can see it again too large of a file for here. After viewing the video there were some that mentioned that the port bucket may not be adjusted properly. Some history, the boat is kept at a marina and the shop at the marina pulled apart the port jet pump and said the impeller and wear ring looked good and the clearance was proper. When I got my boat back to my house I moved both of the throttle handles and the reverse buckets are both being actuated properly with the exact same positioning in the forward and reverse direction. Prior to having this problem, I did put on some jet fins which should not have anything to do with the problem I am having. Earlier today I pulled the clean out plugs which I had to tie a rope to and use a board to get the leverage I needed to pull the plugs, I had rebuild kits for each which I am going to fix tomorrow morning. As some of you may remember I live in a community that does not allow boats to sit out for an extended time so whatever I need to do I may have to move the boat to a storage facility to work on. I was an auto mechanic for many of my younger years so I can do the stuff myself if I could just diagnose. The shop at the marina charged me 250$ for checking out the boat for which they could not determine the problem. I could have replaced one impeller and housing for that price. I am not against changing everything impellers, housings etc. if I know the problem would be taken care of. My plugs definitely needed rebuilding, I should have done that when the boat was in the marina. Could bad clean out plugs have caused the cavitation you can see on the video. Note in the video the engines were running at about 4K RPM and the boat was moving 15 MPH through the water. I have about 5 days max I can keep the boat here otherwise I will need to get it out of here to a storage facility. I have all my tools here so I am hoping someone has seen this before and can advise.

 

[subysti]

Have you checked the intake grates? If they aren't sealed properly or are loose they will cause cavitation. Just small dings and cracks on the impellers can cause it. I'm not sure about your but I know on the new boats the impellers are the same for each side. May be a pain but try swapping them and see if the problem moves to the starboard side. Couldn't find the video on YouTube.

 

[swatski]

@Tom Denion Did you ever post pics of your impellers (taken inside the venturi nozzles - through the steering nozzle opening, or pics shot through cleanout ports, or through intakes at the bottom)?
If I remember correctly you sea trialed the boat with the PO and he was able to get to 40+mph (after a while) albeit accelerating very slowly? wasn't that the story?
I agree with @subysti - this sounds like massive cavitation and could be due to worn out or out of specs wear rings/missing sealant etc. But it could also be aftermarket impellers that were pitched wrong (underpitched, which I think I brought up before) - I had seen amazing amounts of cavitation in pumps with under-pitched impellers first hand, so I would not be surprised.
The cleanout plug rebuilt is a good idea, but I doubt you would be able to reach 40+ if those were shot.

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[Ilmmct]

@Tom Denion sorry you are having these problems. They guys that have responded so far, are higher skilled and can help you trace the cause.

To answer one of your questions, I don't think the cleanout plugs are causing the cavitation. The rebuild kit is maintenance you should do, but it does not expain the high RPMs your Port engine is shooting up to, while the starboard stays consistent, about 29 seconds into your video:

 

[Tom Denion]

Thanks to all I am going to replace the pump impellers and housings and reseal the input grates. I did not post pics of the impeller and wear rings, I am going to pull them apart today and I will post pics when i get it apart, Does anyone have a link to the disassembly of the pumps, I saw one on you tube some time ago but cant find it now?

 

[Tom Denion]

The video is available at IMG 0529 I just checked it, it is on utube.

 

[Julian]

FYI....should you ever want to include a video in the future....just click on the "Film Strip" icon on the tool bar and when the window pops up, paste in the URL for your Youtube (or other) video and voila...it will appear in your post.

The video is available at IMG 0529 I just checked it, it is on utube.

llmct already embedded it above.

Here is the FAQ on pulling a pump:
https://jetboaters.net/faq/how-to-pull-your-jet-pump-something-stuck-in-my-pump-engines-dont-get-to-full-rpm.61/

 

[Tom Denion]

I got the port impeller out today however one of the wear ring bolts had such a thin head I could not get a socket on it so I put it all back together. I went to the shop that put that thin head bolt, he told me to grind off the washer and I should be able to get a socket on it. I asked him why they use a bolt with such a thin head he said that was all they have around, he was a real jerk to put it mildly. One thing I noticed when I removed the intake grates, the space between the hull and the end of the grates was about a 1/4 inch which had no seal whatsoever, I am going to reseal the grates does anyone know what type of sealant should I use, I looked through the service manual and did not see the recommended sealant. Additionally, the gap between fiberglass hull and the end of the grate is quite large 1/8 to 1/4 of an inch, would high quality silicone be sufficient to fill that gap?

 

[subysti]

That is almost certainly your issue. It should be sealed tight, its causing bubbles by being loose. My shop manual just says silicone sealant.

 

[bronze_10]

How does the grate look on the starboard side?

 

[Tom Denion]

I pulled both grates they both had a large gap where the fiberglass hull meets the edge of the grate. Are you sure on the silicon? the sealant that was on there was black and did not look like silicon.

 

[Gary Traina]

If your going to do all that work I would check with dealer for correct sealant so you don't have to do it again, just saying!

 

[Tom Denion]

I agree the repair manual says use silicon, however, there are many different silicon sealants. I will check before I actually pull things apart.