Yamaha 242 limited

[Tom Denion]

My yamaha 242 is cavatating real bad, the boat is unuseable, the impellers and wear ring are in good shape the mechanic says. There is no blockage or plug problems. Will the intake grate not being sealed properly cause this problem? The mechanic does not know what the problem is. Both engines have the same problem, can someone give me an idea to suggest to the mechanic. He asked me to post the problem to see what comes up.

 

[robert843]

My yamaha 242 is cavatating real bad, the boat is unuseable, the impellers and wear ring are in good shape the mechanic says. There is no blockage or plug problems. Will the intake grate not being sealed properly cause this problem? The mechanic does not know what the problem is. Both engines have the same problem, can someone give me an idea to suggest to the mechanic. He asked me to post the problem to see what comes up.

Is this mechanic at a dealer? If so pick a new dealer lol. Your grates being unsealed would not make the boat unusable unless they were basically coming off. I would reinspect the wear rings and impeller your self and make sure they look good it doesn't take much to cause the boat to cavatate in that department. Check the pump cones make sure they look alright and stick your hand up in the intake grate and make sure there is nothing in there on the inside. Pictures always help if you can get us some pics of the grate and impeller it would help us diagnose. Also check that your reverse gates appear to be lined up correctly and the pump nozzles at the end. Last one is make sure your hull is free and clear of debris if you leave your boat in the water long periods growth can cause this as well.

 

[Mainah]

I agree with @robert843. If your hull is clean, engines running properly, impellers/wear rings/shafts/tunnels all in good shape and free from debris then you should be fine. Boat not being overloaded, tied to the dock, or anchored down helps too but I figured you have that covered. It does not take much damage at all to the impellers to cause cavitation. Pull the pumps, take photos, and let the experts here give their opinion.

Good luck!

 

[OperationROL]

My yamaha 242 is cavatating real bad, the boat is unuseable, the impellers and wear ring are in good shape the mechanic says. There is no blockage or plug problems. Will the intake grate not being sealed properly cause this problem? The mechanic does not know what the problem is. Both engines have the same problem, can someone give me an idea to suggest to the mechanic. He asked me to post the problem to see what comes up.

Where are you located. Someone on the site may be willing to help you out in person.

 

[Scottintexas]

Welcome to the forum, we're glad to you found us,

I couldn't vote on your poll as I'm not sure what you were asking,

I echo what the others have said above with a double helping of "you should find a new mechanic".

A few more questions that will help us diagnose your problem and hopefully help your mechanic fix it,

1. Have you owned your boat since new, if not how long
2. How many hours are on your engines
3.Do you boat in fresh or salt water
4.Does your boat get yearly maintenance, if so, what
5.When was the last time your boat was running correctly
6.what makes you think you have cavitation, what symptoms are you having
7.did the problem happen all at once or has it gotten worse over time

 

[buckbuck]

Are the clean out plugs installed?

 

[rkluck]

And installed properly.

 

[haknslash]

'Unusable' boat cavitation sounds like cleanout plugs are not seated or something to me. Usually if it's the impellers you can at least modulate the throttles to help cope but if your boat won't plane then sounds like you're losing a lot of thrust so I would look into your cleanout plugs again. Do you usually have a lot of water in the tubes after boating? When I didn't have a plug seated it didn't make that typical 'wah wah wah wah wah' cavitation sound and "slipping clutch feel" but rather just the engine revs up and there's no thrust but you'll hear a ton of water spraying up and out of the tubes and eventually flowing from the swim deck. I've left my plug out once or twice by accident and it was easily evident by the lack of thrust and it feels completely different than how cavitation feels and sounds.

Is this boat new to you or have you had it a while? What's the history of the boat? Your profile says you have an E series but that's not possible in 2014.

 

[Tom Denion]

Thanks to everyone that responded, I am new to this forum and I really don't understand the vote thing I am in the process of getting pictures of the wear ring and intake grates. The cleanout plugs are seated properly the mechanic also verified. I am in the process of getting pictures of everything for you all to look at, please excuse my ignorance in using all the bells and wistles of this forum.
I bought the boat used 133 hrs on it
When I test drove in in Maryland it was able to get up to 50 MPH I was not driving it but the driver accelerated slowly
Shipped it to TX and removed and cleaned both of the plugs and put them back in, they are locked and in place properly, mechanic agrees the plugs are in properly.
It is run in fresh water now for the first 2 years it was run in salt water
When I come up on the throttle both engines both engines will go to 7K RPM but the boat goes no where.
The mechanic told me when he test drove it he was able to get it up to speed after a long time playing with both throttles.

Hopefully this answers all the questions raised above.

Just a FYI I am 61 years and I was an auto mechanic for 18 yrs, these things look inceditably easy to work on, however where I live now (TX) the homeeowners association does not allow boats in front of houses for more than 2 days, that is why I left it at the marina to get fixed.

Again thanks to all, could someone explain the question that involve voteing I do not have a clue.

 

[haknslash]

Welcome to the forum!

When you get a chance take a picture of the impellers. Cavitation burn marks will be easy to spot with a flash light. Impellers should also have sharp edges with no dings or rough edge.

Cavitation will look like this:

 

[tdonoughue]

@Tom Denion , adding my welcome! What everyone has said to check is correct above. But I note you are in Texas. Several of us are. If you let us know where, perhaps someone can come by and take a peek. With an issue as big as you describe, I bet it would be evident to one of us who has had one for a few years.

I am in the Houston area, near Lake Conroe. Would happy pop by today, but I am on an outbound flight to India. But there are others here and elsewhere in TX. Just put the ask out there.

 

[Neutron]

Welcome to the forum!

When you get a chance take a picture of the impellers. Cavitation burn marks will be easy to spot even if looking from the rear of the pump with a flash light. Impellers should also have sharp edges with no dings or rough edge.

Cavitation will look like this:

Great video. One question regarding it. Is that showing excessive clearance between impeller and housing or is it just the video angle

 

[haknslash]

Great video. One question regarding it. Is that showing excessive clearance between impeller and housing or is it just the video angle

I'm not sure what PWC that video is from but yes that is a big gap compared to our boats wear ring. Look at how ragged the veins on the pump housing are too. That PWC has lived a rough life in shallow water.

Our max gap limit is .024" (0.60 mm).

 

[Britboater]

Welcome to the forum, and the best forum by far, you'll have no problem getting to grips with navigating around the site as it must be one of the easiest around.

Straight away something gets my attention, you mentioned with the water test, the previous owner accelerated slowly and your mechanic managed to get up to speed, slowly. This to me suggests the previous owner knew of the problem and the issue is almost defiantly impeller related. That video is a very good example of excess wear in the liner, if yours has any sort of gap like that, my guess is you've found your problem.

 

[haknslash]

Yup the fact the previous owner accelerated slowly to get on plane makes me think he knew it had an issue. If you have some feeler gauges you can check the gap between the wear rings and the impellers. Anything greater than .024" is out of spec. The mechanic may not have even inspected the wear ring gap and may have just visually inspected for cavitation wear or dings on the impellers.

 

[Julian]

@Tom Denion you are correct that these boats are easy to work on. Sounds like your mechanic doesn't know how to work on jet pumps. This should be a pretty easy problem to diagnose, the members above all have great suggestions. This will likely end up being one of the following:

1. Clean out plugs aren't seated properly
2. Clean out plug "skirt" has deteriorated and needs to be replaced (also called manhole cover replacement kit)
3. Intake grate is missing sealant and/or is damaged
4. Impeller clearance is to large
5. Impellers are damaged and causing cavitation
6. Impeller bearings are shot (listing this last...unlikey both would be bad at the same time) FAQ on replacing bearings

Do both engines cavitate the same way or does one run better than the other (not sure if you tried accelerating with just one at a time to isolate the problem). Most of these boats won't make it to plane on just one engine (not sure about yours).

The pumps come off very easily-check out the FAQ on how to do this....you will find it is simple!

And welcome! As others have said, if you add your location to your profile, experts near you may offer to assist you...we are a helpful bunch! I put URL/Links in for you as best I could to help you find the pertinent information.

 

[Julian]

Another approach is to read through some of the posts here on cavitation and see what other members discovered. Many have photos of the items I listed above....like missing sealant etc.

 

[MrMoose]

@Tom Denion, I'm sorry to hear about your initial impression and problems. For starters, I'm not being sarcastic, but don't bother wasting your time and money with the mechanic that you've been working with. I can't see that any of the forum advice that you've received thus far is incorrect.
I have a 2015 model that has a different hull design, so maybe my insight is not directly applicable. What I can tell you though is that at almost 100 hrs with fresh and some salt water, the only time that I've experienced cavitation is when I got a plastic bottle cap stuck in my impeller. Other than that time and when the boat leaves the water, I experience zero cavitation period, not from a standstill, and not in the most extreme turns.
If I were you, considering that you're mechanically inclined, I'd pull the grates, and look up into the tunnels and see if something doesn't look right like pitting or chips on the impellers, or anything that would impede the smooth flow of water to and from the impellers. Some posts have identified twigs stuck in the impeller that have created cavitation.
Who knows, maybe the time in the salt degraded your grates and tunnel enough to make them cause cavitation, but I don't really have enough experience with that to have a real opinion.
If you're experiencing this problem with both drives, then you might assume that there's a corrosion/wear issue and replace both impellers/wear rings/grates, and be done with it. ... with a mechanic who is certified to work on Yamaha boats.

 

[robert843]

7000 Rpm and the boat won't come up to speed that sounds like a lack of pressure in the pump. Are you clean out plugs difficult to seat and remove? they should easily slide in and pull out if you have to force them down or tug on them hard to get them out you may need to rebuild them. This sounds more logical now then most other option unless the impeller and wear rings were really rough but that would have been easily identified. I would try and get a pic of the plugs seated and unseated as well but by pictures that may still be tough for any of us to identify.

 

[Tom Denion]

@Tom Denion, I'm sorry to hear about your initial impression and problems. For starters, I'm not being sarcastic, but don't bother wasting your time and money with the mechanic that you've been working with. I can't see that any of the forum advice that you've received thus far is incorrect.
I have a 2015 model that has a different hull design, so maybe my insight is not directly applicable. What I can tell you though is that at almost 100 hrs with fresh and some salt water, the only time that I've experienced cavitation is when I got a plastic bottle cap stuck in my impeller. Other than that time and when the boat leaves the water, I experience zero cavitation period, not from a standstill, and not in the most extreme turns.
If I were you, considering that you're mechanically inclined, I'd pull the grates, and look up into the tunnels and see if something doesn't look right like pitting or chips on the impellers, or anything that would impede the smooth flow of water to and from the impellers. Some posts have identified twigs stuck in the impeller that have created cavitation.
Who knows, maybe the time in the salt degraded your grates and tunnel enough to make them cause cavitation, but I don't really have enough experience with that to have a real opinion.
If you're experiencing this problem with both drives, then you might assume that there's a corrosion/wear issue and replace both impellers/wear rings/grates, and be done with it. ... with a mechanic who is certified to work on Yamaha boats.

Thanks the problem I have the boat is at the marina workshop and the mechanic cannot determine the problem, on Monday I am going to tell him to put it back together and I will check it out pull both pumps and check the grates this forum has been so helpful thanks for your ideas.