2015 Limited S with low RPM issue

[rkgdmd]

Hi Guys. I was hoping to do a fairly comprehensive review of my 2015 Limited S, but I've had an issue come up and wanted to see if anybody has had this problem before. I traded my CARB compliant 2013 Limited on a non CARB 2015 Limited S. I was hoping to see a little more top end than my other boat, but was unpleasantly surprised to find that it was significantly slower. Top speed (@ sea level) was about 39-40 mph. RPM max was about 6900-7000. I adjusted the throttle cables but no change. Dealer sent out a service tech and when he put the engines on computer he noticed that the throttle bodies were only opening to 80%. He had no idea what the problem could be and said the dealer would call Yamaha with a possible fix. Any ideas?

 

[tdonoughue]

I got nuthin.

If it weren't for the low performance, I might guess that the 80% was them doing something to make it run better at altitude (where being able to go to 100% would make it run better). But with the low performance... I think it's broke.

 

[rkgdmd]

What's wierd is that the limited throttle opening is exactly the same on both engines. You would think that if something were broken, it would be limited to only one engine or the amount of opening would vary between the two. My dealer promised to call Yamaha the next day, but of course they didn't, so now I have to wait until next week. I'll keep you posted.

 

[haknslash]

Are the throttle bodies on these motors mechanically or electronically controlled? The fact both engines are doing it doesn't make me think something is broken. If the throttle bodies are electronically controlled I can see this being a ECM related issue or setting being the cause.

 

[Julian]

Now there are two people complaining about 2015s with low rpm issues....

http://www.jetboaters.net/threads/top-speed-rpm-question.6393/

 

[0627Devildog]

Should we add it to this thread?

https://jetboaters.net/threads/the-2015-24x-issues-thread.3801/page-6#post-105265

 

[john94si]

I have noticed speeds do vary on our 15 242 LS also. But last week i got this out of it on a smooth lake.
51mph

 

[rkgdmd]

Are the throttle bodies on these motors mechanically or electronically controlled? The fact both engines are doing it doesn't make me think something is broken. If the throttle bodies are electronically controlled I can see this being a ECM related issue or setting being the cause.

I am no expert, and I'm sure someone with more knowledge will chime in, but there is both a mechanical and electronic component to throttle operation. The throttle levers move a mechanical switch which in turn sends a electronic signal to the ECM to open the throttle body.

 

[haknslash]

Now there are two people complaining about 2015s with low rpm issues....

http://www.jetboaters.net/threads/top-speed-rpm-question.6393/

Which other user?

 

[subysti]

I'm thinking altitude or ECM issue. You have independent cables going to independent electronics opening the throttle bodies so if they are both doing it the ECM is telling them that or the throttle adjustment was done wrong on both. I'll see if the shop manual has anything.

 

[Willard Ivins]

When a technician puts diagnostic instruments on the system and finds that the throttles bodies both are opening only 80%, that is a problem within the black box, the throttle position sensor, or the mechanism opening the throttle valve. Altitude tuning deals with fuel/air ratio, not throttle valve opening. To get maximum performance / rpm from an engine, the throttle valve needs to reach 100% opening, or 90 degrees opening to the air flow, regardless of altitude.

 

[rkgdmd]

I'm thinking altitude or ECM issue. You have independent cables going to independent electronics opening the throttle bodies so if they are both doing it the ECM is telling them that or the throttle adjustment was done wrong on both. I'll see if the shop manual has anything.

Hi @subysti ....don't think it's altitude as I am at sea level.

 

[subysti]

here is the throttle adjustment procedure if you want to try and see if its correct. It may have been done incorrectly either at the factory or dealership.

 

[rkgdmd]

here is the throttle adjustment procedure if you want to try and see if its correct. It may have been done incorrectly either at the factory or dealership.

Hey @subysti....I have adjusted the mechanical throttle linkage as per the JBP video. Am I correct that the procedure outlined in the service manual requires a computer with the Yamaha diagnostic software?

 

[subysti]

I think so but I think you can also do it if you're good with a digital volt meter.

 

[Willard Ivins]

A volt meter will suffice. The manual should give appropriate values for closed and 100% open.

 

[rkgdmd]

Ok...sorry....having a little trouble understanding the service manual and exactly where to take those voltage readings from. Any help would be greatly appreciated.

My dealer really is useless. They said Yamaha no longer gives them service manuals...that parts of it can be downloaded, by them, as necessary. ..so they have no idea what I am referencing when talking about those voltages. They also initially told me that a throttle opening of 80% was OK???? After some "explaining" on my part, they are coming today or tomorrow to do a throttle cable adjustment. ...which of course I've done already, but at least there admitting there may be something wrong.

 

[Jonathan Pisarczyk]

Did anyone get the issue resolved? I must be having the same problem.

 

[Craig]

Still having the same problem, it's going back to the dealer soon for this and the extra water it takes on every outing.

 

[rkgdmd]

Still having the same problem, it's going back to the dealer soon for this and the extra water it takes on every outing.

Hello @Craig . If and when the dealer finds the source of your leak, please let me know. I have the same year and model as you and have not been able to determine where my leak coming from. I think I may need to remove my clean tray cover next as I have exhausted all other areas. Thanks.