Yamaha 242 limited

[Tom Denion]

OK thanks, my boat is in the water now I am going to make a video of my problem and post it, I am waiting on my neighbor to go out with me. I can't go out by myself because I am crippled with Multiple Sclerosis (35 yrs) and I need help getting on and off the boat. After making the video I will be driving back to Maryland for a couple of months. Depending what everyone thinks of the video, I will just replace everything impellers, housings, plug seals, and intake grate's. I just want to cover all my bases, if anyone knows of anything I should replace let me know, I will throw anything at this problem I can. I will be doing the work myself and I don't really care about the cost of the parts at this point, I just want my kids to be able to go skiing this summer. As always thanks to each and every one of you all of you.

 

[swatski]

OK thanks, my boat is in the water now I am going to make a video of my problem and post it, I am waiting on my neighbor to go out with me. I can't go out by myself because I am crippled with Multiple Sclerosis (35 yrs) and I need help getting on and off the boat. After making the video I will be driving back to Maryland for a couple of months. Depending what everyone thinks of the video, I will just replace everything impellers, housings, plug seals, and intake grate's. I just want to cover all my bases, if anyone knows of anything I should replace let me know, I will throw anything at this problem I can. I will be doing the work myself and I don't really care about the cost of the parts at this point, I just want my kids to be able to go skiing this summer. As always thanks to each and every one of you all of you.

Cool! I'm really curious what you find.
If you get a chance to have your neighbor look into the cleanout tunnel you will be able to see the "leading edge" of the impellers, that may help, too. The OEM has a long neck, like nothing else on the market.
Here is an OEM, Solas Concord, and Skat Trak (from L to R):




Solas or Skat can have a cone (the one on the left here):


If you have the boat on a trailer, please also shoot some pics through the nozzle in the back, as @haknslash showed above.

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[Tom Denion]

OK will do, I now have a video I will post, just got in.

 

[Tom Denion]

Hi everyone, I have uploaded a video to utube of my problem, note the port engine really has the worst problem, the SB engine too went through uncontrolled reving. Note throughout this video these engines are tacking 4K and the boat never goes over 10 mph. Please let me know what you think.

 

[swatski]

Hi everyone, I have uploaded a video to utube of my problem, note the port engine really has the worst problem, the SB engine too went through uncontrolled reving. Note throughout this video these engines are tacking 4K and the boat never goes over 10 mph. Please let me know what you think.

Yes - this is BAD! IDK. Terrible cavitation. We would need to see some pictures of the intake tunnels, impellers and wear rings!

Is there any way that you could pull the pumps? You will need to do that anyway.

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[Tom Denion]

I plan to replace impellers wear rings etc. on both engines, these drives were torn down by a mechanic who said everything look ok and he did not want to just start throwing parts at it.

 

[Tom Denion]

When your Yamaha engines 4K how fast is your boat going?

 

[swatski]

When your Yamaha engines 4K how fast is your boat going?

Maybe 20-25mph

Do your engines rev up all the way to 7,800rpm and hit the rev limiter?

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[swatski]

Hi everyone, I have uploaded a video to utube of my problem, note the port engine really has the worst problem, the SB engine too went through uncontrolled reving. Note throughout this video these engines are tacking 4K and the boat never goes over 10 mph. Please let me know what you think.

I can't tell if your speedometer is working, is it? Did your take any pictures when your mechanic had the pumps out?

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[ToddW850]

Thanks for the video. On top of what's been mentioned just now by @swatski , I'm curious what the water looked like behind your boat. Does it look like you are getting propulsion in the water flowing behind the boat? I'm curious if it's consistent with other boats at those speeds/rpms.

 

[ToddW850]

JUST HAD A THOUGHT! Do your buckets move up and down over the jets nozzles like they are supposed to? I believe this could be your cause. If the buckets don't move up all the way and clear the jet nozzle opening, then the boat won't go like it should. Have you checked this prior?

Could be easily checked. Have someone in the Captains Chair move the throttles forward and reverse, while you stand at the back of your boat looking for the buckets to move up and down. Make sure you are getting full upward and downward movement. Engines off obviously.

 

[ToddW850]

Here is a video I posted on YouTube. It's a different issue. I had an engine that wouldn't start (ended up being clogged fuel injector). I ran back on one engine. I've done it before without issue (had fishing line wrapped around impeller).

But in this video, I didn't think to at least put the throttle up on the nonrunning engine, to allow water to flow through. I THINK this may be why I could not get on plane and could not go more than 5-10 mph. Because the bucket being down would act more like a small parachute. I don't know, but that's what I'm thinking.

Again, different reason, but sounds like the same symptom as to not wanting to go.

 

[haknslash]

I could see how a reverse bucket not properly adjusted could cause an issue. But what is the likelihood that both are that bad out of adjustment? It could certainly happen though so I wouldn't rule it out of possible causes and it's something he can easily check. I would imagine he would be able to feel the vibration in the binnacles if the buckets were out of adjustment?

Swatki's suggestion that it may be improperly pitched aftermarket impellers could also be likely cause but how many people with boats actually buy aftermarket impellers? Do the stock ones wear out that soon that a boat built in 2014 needs new impellers within 3 years? I would have to imagine that most owners of these boats aren't that willing to mod the boats for a certain impeller performance. If we were talking PWC's then sure I could see the owner ratio of those with aftermarket impellers higher than those still with stock ones.

I still keep trying to look at this from the most common ground issue of things we know in absolutes. What we know for certain is that he said he had issues with removing and installing the plugs when he bought the boat. So that's already an indicator of an issue. So much that he took the time to clean them prior to making this thread so that makes me think he also suspected something wasn't just right with how difficult his plugs are to operate.

That video he posted is looks like zero thrust. The speedo is hardly moving! When my cleanout plug wasn't sealed and I pulled away from the dock under power is was the same like in his video with zero thrust and wasn't the same kind of sound you have with cavitation where you can literally hear and sort of 'feel' the disrupted turbulence from the cavitation.

For trying to tackle this problem, if it were my boat I would not go and start buying new impellers, wear ring, etc. I would start looking at what is the most likely problem and cheapest solution first and then move from there. Throwing a bunch of darts at a problem board and hoping one of them fixes the issue isn't going to help you know just what went wrong. Take it in chunks and use the process of elimination before splurging on a bunch of parts. You already know your plugs are going to need to be rebuilt because they have swollen ....or something is causing them to be hard to use, so that's out of the way. I would start there along with ensuring your reverse buckets are within spec of adjustment. I would also inspect the wear ring gap and inspect to see what kind of impellers you have. If the wear ring gap is within spec then take the boat out to sea trial your new rebuilt cleanout plugs. If you still have an issue after that then you will know its not the plugs, the buckets or the wear ring. I'm just saying do the simple checks and fixes first before spending and possibly wasting $$$.

 

[swatski]

I would definitely not go and start buying parts, before getting to the bottom of it. What parts?
Maybe it is time to have a Yamaha boat dealer/mechanic look into this? I did take the side of the mechanic involved initially, but after seeing this - something is amiss here big time. I also am having hard time picturing this boat doing 50mph, aside from that I'm am not sure the speedo is actually working.

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[swatski]

Here is a video I posted on YouTube. It's a different issue. I had an engine that wouldn't start (ended up being clogged fuel injector). I ran back on one engine. I've done it before without issue (had fishing line wrapped around impeller).

But in this video, I didn't think to at least put the throttle up on the nonrunning engine, to allow water to flow through. I THINK this may be why I could not get on plane and could not go more than 5-10 mph. Because the bucket being down would act more like a small parachute. I don't know, but that's what I'm thinking.

Again, different reason, but sounds like the same symptom as to not wanting to go.

I think that is EXACTLY the problem the OP is experiencing - extreme impeller slippage.
However I do not think the buckets are involved. The video clip you show (running on one engine) provides a direct demonstration of the pump cavitation under excessive load - every Yamaha twin will behave like that, whether or not the "off" pump's bucket is lifted or not. (I agree that keeping the "off" engine bucket/throttle up/on is important, but that is primarily to prevent swamping the exhaust and possibly hydrolocking the engine). The only way to prevent or diminish that would be to use a massively overpitched impeller (which would lug and bog the engine down), or use anti-cavitation cones (such as L13) with an enlarged (bored out) venturi nozzle.

In other words, when running with an underpitched impeller, it will spin and slip with little thrust - just like in the clips - until the boat picks up speed forcing pump loading through the intakes.

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[Tom Denion]

Maybe 20-25mph

Do your engines rev up all the way to 7,800rpm and hit the rev limiter?

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Yes when the rev up all the way they do hit the rev limiter.

 

[swatski]

Yes when the rev up all the way they do hit the rev limiter.

That makes sense, and your engines sound fine so at least no worries there (I think).

This has got to be mismatched impellers. Or, something else - relatively simple.

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[Tom Denion]

I could see how a reverse bucket not properly adjusted could cause an issue. But what is the likelihood that both are that bad out of adjustment? It could certainly happen though so I wouldn't rule it out of possible causes and it's something he can easily check. I would imagine he would be able to feel the vibration in the binnacles if the buckets were out of adjustment?

Swatki's suggestion that it may be improperly pitched aftermarket impellers could also be likely cause but how many people with boats actually buy aftermarket impellers? Do the stock ones wear out that soon that a boat built in 2014 needs new impellers within 3 years? I would have to imagine that most owners of these boats aren't that willing to mod the boats for a certain impeller performance. If we were talking PWC's then sure I could see the owner ratio of those with aftermarket impellers higher than those still with stock ones.

I still keep trying to look at this from the most common ground issue or things we know in absolutes. What we know for certain is that he said he had issues with removing and installing the plugs when he bought the boat. So that's already an indicator of an issue. So much that he took the time to clean them prior to making this thread so that makes me think he also suspected something wasn't just right with how difficult his plugs are to operate.

That video he posted is looks like zero thrust. The speedo is hardly moving! When my cleanout plug wasn't sealed and I pulled away from the dock under power is was the same like in his video with zero thrust and wasn't the same kind of sound you have with cavitation where you can literally hear and sort of 'feel' the disrupted turbulence from the cavitation.

For trying to tackle this problem, if it were my boat I would not go and start buying new impellers, wear ring, etc. I would start looking at what is the most likely problem and cheapest solution first and then move from there. Throwing a bunch of darts at a problem board and hoping one of them fixes the issue isn't going to help you know just what went wrong. Take it in chunks and use the process of elimination before splurging on a bunch of parts. You already know your plugs are going to need to be rebuilt because they have swollen ....or something is causing them to be hard to use, so that's out of the way. I would start there along with ensuring your reverse buckets are within spec of adjustment. I would also inspect the wear ring gap and inspect to see what kind of impellers you have. If the wear ring gap is within spec then take the boat out to sea trial your new rebuilt cleanout plugs. If you still have an issue after that then you will know its not the plugs, the buckets or the wear ring. I'm just saying do the simple checks and fixes first before spending and possibly wasting $$$.

I can't tell if your speedometer is working, is it? Did your take any pictures when your mechanic had the pumps out?

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Yes the speedometer is working, the test drive of the boat it got up to 50 MPH

 

[swatski]

Yes the speedometer is working, the test drive of the boat it got up to 50 MPH

Well then it has got to be underpitched impellers. I think. I can not imagine you would be doing 50mph if it is a cleanout plugs' issue, as in not-set or w/blown seals.
Basically, just like underpitched propellers in a prop boat, those will slip during hard acceleration/hole shot, but can give better top speed. It's just your case seems pretty extreme.

Those are all just my personal opinions, I am not a mechanic or a Yamaha expert.

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[Tom Denion]

I could see how a reverse bucket not properly adjusted could cause an issue. But what is the likelihood that both are that bad out of adjustment? It could certainly happen though so I wouldn't rule it out of possible causes and it's something he can easily check. I would imagine he would be able to feel the vibration in the binnacles if the buckets were out of adjustment?

Swatki's suggestion that it may be improperly pitched aftermarket impellers could also be likely cause but how many people with boats actually buy aftermarket impellers? Do the stock ones wear out that soon that a boat built in 2014 needs new impellers within 3 years? I would have to imagine that most owners of these boats aren't that willing to mod the boats for a certain impeller performance. If we were talking PWC's then sure I could see the owner ratio of those with aftermarket impellers higher than those still with stock ones.

I still keep trying to look at this from the most common ground issue or things we know in absolutes. What we know for certain is that he said he had issues with removing and installing the plugs when he bought the boat. So that's already an indicator of an issue. So much that he took the time to clean them prior to making this thread so that makes me think he also suspected something wasn't just right with how difficult his plugs are to operate.

That video he posted is looks like zero thrust. The speedo is hardly moving! When my cleanout plug wasn't sealed and I pulled away from the dock under power is was the same like in his video with zero thrust and wasn't the same kind of sound you have with cavitation where you can literally hear and sort of 'feel' the disrupted turbulence from the cavitation.

For trying to tackle this problem, if it were my boat I would not go and start buying new impellers, wear ring, etc. I would start looking at what is the most likely problem and cheapest solution first and then move from there. Throwing a bunch of darts at a problem board and hoping one of them fixes the issue isn't going to help you know just what went wrong. Take it in chunks and use the process of elimination before splurging on a bunch of parts. You already know your plugs are going to need to be rebuilt because they have swollen ....or something is causing them to be hard to use, so that's out of the way. I would start there along with ensuring your reverse buckets are within spec of adjustment. I would also inspect the wear ring gap and inspect to see what kind of impellers you have. If the wear ring gap is within spec then take the boat out to sea trial your new rebuilt cleanout plugs. If you still have an issue after that then you will know its not the plugs, the buckets or the wear ring. I'm just saying do the simple checks and fixes first before spending and possibly wasting $$$.

Thank you for your in-depth analysis of my problem. You are the first to mention the adjustment of the reverse buckets, I will look that up in my service manual. I agree with you fully about throwing darts and trying to find the problem that way. I am definitely going to rebuild my plugs. The boat is at a marina and I will bring the plugs to my house to be rebuilt and then I will make a sea trial, that is very good advice thanks. If that doesn't solve it I will tear down the thrust units. If this not solve the problem I will go ahead and replace impellers/wear ring etc. If I were younger and didn't have MS, I would be working on it like you suggest isolating the problem, however, I am 61 and can barely walk that couple with my HOA allows boats in driveways for a maximum of 2 days so I need to make a full assult by changing everything. One thing that concerns me is that yesterday (when the impellers were not cavitating) the engines were tacking 4K and the boat would only go 10 MPH. It seemed that we were dragging an anchor. Thanks again, I will be leaving TX for about 2 months so I will get back on this when I return in late May, Thanks again