Top Speed RPM Question

[tdonoughue]

Perhaps it is part of the design making them quieter...

 

[john94si]

Florida sea level smooth lake
15 242 ls

 

[OrangeTJ]

Almost guarantee that density altitude is a factor.

 

[msavold]

Hmmm... I may be off base here but the engines are fuel injected so I would think the brains should take care of leaning the fuel mixture to compensate for the increased density altitude, no?

What's the air temperature? Since @Huskerjetboat is running in NB, I'm guessing that the air temp is lower that what many of us see regularly at sea level. I know our local airport (elevation 600') was reporting a density altitude of 2500' just the other day when the temp was in the high 80s. So, many of us - running at sea level - have engines that are operating in an air density similar to over 2000', and we don't see the same speed/rpm limits.

I suspect something else - a rev limit setting or some such other adjustment? Something with the injectors? Brains?

 

[McMark]

Could the air filters be a little fouled with oil? I'm sure the ecu would compensate by giving a little less fuel.

 

[Huskerjetboat]

2nd thread with a 2015 with low rpm....hummmmm

http://www.jetboaters.net/threads/2015-limited-s-with-low-rpm-issue.6387/

It's a 2013.

 

[Huskerjetboat]

Have not yet done 10 hour service, so plugs have not been changed. Picked boat up last September new leftover 2013 stock. Only have like 6-8 hours on it. Haven't looked at exact time lately. Dealer kind of alluded that there may be an unpublished break in period where RPM's are limited for the first so many hours. Does that sound possible?

 

[Craig]

Were there CARB boats in 2013?

Certainly were, our previous boat was a '13 carb model AR 240. I saw 48 mph once in it with 1/4 tank and three people at top end. Bad thing is so far I'm not even seeing 48 on our current boat.

 

[tim2808]

I have a 2013 ar192 and could only get 7200 rpms until I reached about 75 hours on her. Now I can get about 7,800. Take that for what it's worth but I still think there is some kinda computer limiter. Because the only thing I did between this year and last fall was get the oil changed and all this year I have been able to go faster/higher rpm.

 

[rkgdmd]

It's a 2013.

It's a 2015

 

[Huskerjetboat]

2nd thread with a 2015 with low rpm....hummmmm

http://www.jetboaters.net/threads/2015-limited-s-with-low-rpm-issue.6387/

When I said its a 2013 I was responding to this quote as well as the one about the quiter thing. It's all good, except for my RPM issue, not good.

 

[Huskerjetboat]

From responses so far, I would think I should be getting at least 7,500 rpm, even with altitude, which is not that high in the plains. I bought the boat from River Valley Powersports in Rochester. A six hour drive from Omaha and 9 from the lake where my boat is. The dealer in Omaha has a less than stellar reputation. So.... It's not an easy thing for me to take back to the dealer. We have another dealer in town that is authorized to work on Yamaha jet ski engines, and would be able to do warranty work on it. They only sell yamaha jet skies, and they are a much better shop. May have to take it to them.

 

[OrangeTJ]

Just a note that fuel injection does help to ensure that the fuel air mixture is correct but the only way it can do that as altitude increases is to reduce fueling. Accordingly, you get less power, which equates to less rpm and less speed. If density altitude at 600 feet can be 2500 feet, at 2500 feet it can be more like 3500 to 4000. Our sx210 will run 8200 rpm at 400 feet elevation on a cool dry day. At 4000 feet on simar conditions it will turn 7200 max. We are up at Lake Tahoe this week and max rpm is about 6900 up here at 6400 feet. Top speed is about 32 up here vs 45 ish at 400 feet of elevation.

Different engines and boat, I know, but clearly altitude has an effect .

 

[OrangeTJ]

Have you checked to ensure that advancing the throttle levers all the way forward results in the throttle linkage in the engine compartment is going all the way to the stop for each engine? Easy to adjust if not.

 

[Huskerjetboat]

Have you checked to ensure that advancing the throttle levers all the way forward results in the throttle linkage in the engine compartment is going all the way to the stop for each engine? Easy to adjust if not.

No, have not checks that, is that an easy thing to find on the engine? Any pointers on where to look would be appreciated.

 

[OrangeTJ]

Look on the side walls of the engine compartment.

 

[Huskerjetboat]

I came across something on that other site that may be the answer to my issue. Apperantly boats sold in California have emission requirements that take about 1,000 RPM's off the top end. These boats can end up getting sold anywhere. So I am wondering if the boat I bought in Rochester, MN wasn't originally in California? Wonder how I can tell if that is the case? Anyone know? If this is the case it does not make me happy.

 

[Scottintexas]

@Huskerjetboat

I feel for you and don't have an easy answer, I think in that YJB thread the engine # had an identifier code but I could be wrong,

here is a link to a thread we had on the topic,
https://jetboaters.net/threads/california-boat.2913/page-3

 

[Kennc]

@Huskerjetboat I have a 2015 AR240 in NC bought from a NC dealer

It is a 4 star boat (or CA model).

Check the sticker on the port side wall of the engine compartment. It will list MAX POWER in kw/hr.

122 is 4 star boat

132 is standard.

You can Google the conversion to hp to see what you lose with a 4 star.

 

[Speedling]

If you aren't hitting top rpms you need more power or less pitch on the impellers. It is a guessing game and elevation can certainly play a factor. Try for more power by doing a couple of the riva mods or pulling off your filter and see if it makes a difference.