Yamaha 242 Limited S loss of power

[James Kyne]

I have had my Yamaha for a month now and I love it. I recently encountered a big problem through. I noticed a loss of power when I am pulling wakeboard a out of the water. When I first got it there was no problem. Now, after a month I feel a loss in Low end HP. It seems like I have rev up the RPMs higher to achieve maximum speed as well. I could get up to 45mph or so when it was brand new and it still achieves that now. High end power seems fine.
I removed the impeller assemblies on both sides and inspected them. Both look good. No nicks in the blades.

Does anyone have any ideas before I bring it in to the shop?

Thanks, Jay

 

[Williamsone46]

Do you got more specific details of what it's doing now compared to what it did?

 

[McMark]

Pulling a tube/skier/wakeboard gives the boat a different feel. First time I pulled a skier I thought I had something in the impeller. Does the boat feel fine/normal when you aren't pulling the wakeboard we up?

 

[James Kyne]

When I first got it in June I took it out with 1550 lbs of passengers and 300 lbs of fuel. The boat had no problem pulling my big butt out of the water and I weigh 250lbs. I took it out about 6-7 more times during June and early July. This past weekend I had 1530 lbs of passengers and 300 lbs of fuel. When they tried to get me up on the board the boat struggled. I tried several riders and we all struggled to get up. The boat just did not have the low end torque it had a month ago. I read several things online regarding jet boat cavitation and loss of low end power due to impeller damage and jet pump blockage. I removed both impeller assemblies and did a visual inspection for damage. Negative on damage.

Any ideas?

 

[Boat Crazy]

Look around for any lose of or loose silicone. Look in the tube ports and water injection area. That boat should hit 50 as a minimum and 53 tops. You should not feel much if any difference pulling a tube or skier. If you cannot find anything wrong with the silicone, change the spark plugs.

 

[Big Shasta]

If it's cavitation, you'll know it. The RPMs will shoot up with little to no "bite" . If cavitation isn't the issue, the engine is making less power. Make sure the oil isn't overfilled, On the older boats, it would cover the air filters in oil and that would definitely starve the engine for air. Not sure if that's still an issue on the new boats. Make sure you check the oil with the engine hot and level in the water.

 

[Jonathan Pisarczyk]

Maybe you've got some bad gas? Try some fresh 91 Octane! Or possibly some fouled spark plugs.

 

[sysinu]

or you have all of the weight distributed aft in the boat. try moving some people to the bow.

 

[Williamsone46]

You can replace spark plugs make sure you have fresh fuel, check air filters.

 

[rkluck]

Assuming no cavitation problems I thought the bad fuel may be a good idea.
FYI - My boat will not pull people up as well with, I guess about 7 or 8 people, 1500lbs as compared to 3 people). I saw you had about the same weight both times I just wanted to say extra weight will make a difference. I have easily pulled 225lb to 245lb people up and had a full boat of people and stuff, it is just a little slower.

 

[James Kyne]

I took it to the dealer service guy today to have him look at it. He told me right away that it is wear on the impeller on the starboard side. He said that the clearance between the wear ring and the impeller should be like .004". That's about the width of a business card. Mine has twice that. It seems the shallow water of the intercostal here is Pensacola is killing me. Two weeks ago I beached it to hang out on a sandbar and sucked a lot of sand up when I was leaving. The service guy feels that was enough to wear the prop down.

Now, is this cavitation?

Another guy at the dealership advised me to buy a new prop designed for low end torque for better wakeboarding power. Any thoughts?
If so did anyone happen to change theirs on the 242?

Thanks, Jay

 

[sysinu]

Jay,

I tried stock screws at higher altitude than sealevel and didn't get the RPM's needed. Then, I changed my screws out and it was too high pitched (I also did a few performance mods at the same time... oops)... to the point where I could blow out my holeshot with cavitation. It worked amazing at 6K+' altitude, but still rev limited my top-end velocity. I have some tuned impellers now for both altitudes that I boat at and it makes the world of difference. 6K' altitude with the boat loaded heavy for surfing, the high altitude impellers have just the right bite in the water. 3.5k' altitude and they would just over-rev and not shove enough water through.

Where your impeller has too much space in the pump housing, you could see cavitation there, but a different kind than what most of us talk about when we say cavitation. When most of us talk about cavitation, it's where the jet pump cannot intake enough water for the rotation of the impeller's desire to shove water out the pump. This is usually because of issues with the intake grate, altitude, impeller pitch, etc ... but the cavitation we're usually talking about is caused by air. In your case, you might be feeling cavitation, but it's not because of air, instead it's because your impeller not fitting properly into the pump. Imagine threading a screw into a hole that is tapped too large. The screw is going to wobble and not hold solid. That's the cavitation that I think you're feeling and the loss of power is likely from the spacing (too separate issues caused by the same problem). So initially the screw is not stable, but once it gets enough water passing across it, it stables out.


Low-end torque is unlikely your issue. I would just get your impeller fixed/replaced. Where it's a 2015, you should be talking to your dealer to fix a factory related problem, I suspect.

 

[rkluck]

Glad to hear you found the problem but surprised that a new boat would have an issue like this. There are many people that back their boats up to a beach and I am sure at one time or another have sucked some sand through the impellers. I just don't recall this as being a typical problem. I hope the dealer works this out for you.

 

[Bennie]

I took it to the dealer service guy today to have him look at it. He told me right away that it is wear on the impeller on the starboard side. He said that the clearance between the wear ring and the impeller should be like .004". That's about the width of a business card. Mine has twice that. It seems the shallow water of the intercostal here is Pensacola is killing me. Two weeks ago I beached it to hang out on a sandbar and sucked a lot of sand up when I was leaving. The service guy feels that was enough to wear the prop down.

Now, is this cavitation?

Another guy at the dealership advised me to buy a new prop designed for low end torque for better wakeboarding power. Any thoughts?
If so did anyone happen to change theirs on the 242?

Thanks, Jay

Jay -

I live in the same area and make sure to always push out when on a sandbar (Robertson Island). Thanks for the tip though, of the business card, I'll go check on that when I get back in. Our sand is great on our feet, we just have to watch out for our impellers.

 

[Cobra Jet Steering LLC]

I don't think the wear ring etc is the issue, does your boat cavitate on hard acceleration if not your wear ring is probably not bad I put 500 hours on my supercharged s h o before I did a wear ring and impeller . Honestly you may be starting out hard in too shallow water or you may have weeds getting in the pump

 

[SCSTWG]

I highly doubt that sucking up sand once at the sandbar would cause that kind of impeller or housing wear.

 

[TomTom]

I have the Exact same problem now. I had 10 adults and 2 children on the boat this weekend and a few chairs coolers etc. The boat would not go above 12mph at 6k-7k rpms. No matter what I did the boat did not go over that speed. I will be inspecting my impeller this weekend and see what needs to be done. My boat only has 60 hours on it. I can`t believe that it would feel like that already. Has anyone changes their impellers with a solas one for instance? Any advise?

 

[swatski]

I have the Exact same problem now. I had 10 adults and 2 children on the boat this weekend and a few chairs coolers etc. The boat would not go above 12mph at 6k-7k rpms. No matter what I did the boat did not go over that speed. I will be inspecting my impeller this weekend and see what needs to be done. My boat only has 60 hours on it. I can`t believe that it would feel like that already. Has anyone changes their impellers with a solas one for instance? Any advise?

Does it feel the same on both sides? It is almost certainly a pump issue, either damaged/worn out impeller(s), something stuck in between an impeller and a wear ring (could be very small, sized like a match), or missing sealant in the pump/intake tunnel(s) - causing the pump to suck in air and "cavitate"/ventilate.

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[TomTom]

Thank you for your reply. I`m new to boating so not very well experienced with these type of things. I will be checking it this weekend and will let you guys know what I have discovered.

 

[swatski]

Thank you for your reply. I`m new to boating so not very well experienced with these type of things. I will be checking it this weekend and will let you guys know what I have discovered.

If you have the time, check out the FAQ section - you may need to pull the pumps to really check things out including impeller/wear ring tolerances and possibly missing sealant in the tunnel.

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