Yamaha AR240 engine RPM's not in sync.

[C Spez]

Hello I am new to jet boating and new to this forum any suggestions are welcome.
I have a 2018 Yamaha AR240 I bought it new in July of this year, I had the 10 hr service done and boat does not have 50 hours yet.
Since day one the engines RPM have been different by over 500 RPMs and get progressively worse at higher speeds.
I brought it in immediately to the dealer who claims the throttles cables are adjusted properly, the lift gates are in line with each other and the pitch of the impellers is accurate, fuel lines are fine and air filters are clean,
but the issue of the RPMs continues.
Has anyone else experienced this too and is there a solution to getting both of the engines to run at the same RPMs without manually adjusting one throttle ahead of the other?

thank you

 

[swatski]

WHat do you get at WOT? Typically, the PORT side will be faster by about 100-200RPM, as compared to STRBD, due to uneven pump loading. Yamaha used to furnish impellers with differential pitch in the past but in the newer "keeled" 2015+ twin models they don't so both impellers are the same pitch.
You can make adjustments, there are threads on the FAQ section, but it is almost impossible to have the RPM match across the entire RPM range.
The only thing that can solve this issue is @Ridesteady. Highly recommended, synchs the throttles electronically (in non-E models).

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[J-RAD]

I think @swatski is as educated a person on this topic as anyone. His suggestion that the engines may be experiencing different loads to do impeller pitching may be accurate if the boat is mechanically fine in every other regard, and it sounds like it is. @swatski would the Lucky 13 cones be of any advantage or is modifying the impeller itself the way to go?

It sounds to me like your dealer has gone as far with "fixing" the problem as they're willing to which is an awful position to be left in... My option is that the RPM's should be a closer match than 500.

I do second the the addition of a @Ridesteady devise. It's worth every cent. There are some good write ups about it on here.

 

[swatski]

@swatski would the Lucky 13 cones be of any advantage or is modifying the impeller itself the way to go?

In short - yes. I run 2 L13s with three spacers (10mm?) on the port side and no spacer strbd.

500 rpm sound like a lot but I would like to know what is the difference at WOT.

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[Stevenpigsooie]

2016 AR240 with about 50 hours.
There are certain points across the rpm range where mine are off by about 500. I think it’s between 4-6k. This last weekend I was WOT on smooth water, 87 temp, 5mph headwind, full tank, and 2 adults. Port was at 7,400 and starboard 7,100. That’s with newish spark plugs and no other performance mods. We reached 47mph and I’m happy with that. So yes I think it’s normal and varies some from boat to boat.

 

[C Spez]

thank you for your input it was very helpful.
I will have to take it out and run at WOT with the both throttles in line with each other.
As the last time I had the boat at WOT I ran with 100% fuel, 3 people, a large cooler and the ski locker full of towable's. obviously some additional weight. seas were very calm, flat like glass.
I was running at 42 MPH and to get the RPMs to sync at 7050 the starboard throttle was a full handle width ahead of the port side throttle. the starboard throttle was an 1.5 to 2 inches ahead of the port side throttle. I had to pull the port side throttle back to sync the RPMs,
The computer shows the engines at 18 hours - the port side engine has consumed 39 gal of gas and the starboard engine has consumed 36.4 gal of gas.
I know at 16 mph the port side it running at 5335 and starboard at 4725 , 609 RPM's less. when the throttles are in line with each other.
Do you guys think the ridesteady electronic sync device can correct such a large disparity?

thanks

 

[swatski]

thank you for your input it was very helpful.
I will have to take it out and run at WOT with the both throttles in line with each other.
As the last time I had the boat at WOT I ran with 100% fuel, 3 people, a large cooler and the ski locker full of towable's. obviously some additional weight. seas were very calm, flat like glass.
I was running at 42 MPH and to get the RPMs to sync at 7050 the starboard throttle was a full handle width ahead of the port side throttle. the starboard throttle was an 1.5 to 2 inches ahead of the port side throttle. I had to pull the port side throttle back to sync the RPMs,
The computer shows the engines at 18 hours - the port side engine has consumed 39 gal of gas and the starboard engine has consumed 36.4 gal of gas.
I know at 16 mph the port side it running at 5335 and starboard at 4725 , 609 RPM's less. when the throttles are in line with each other.
Do you guys think the ridesteady electronic sync device can correct such a large disparity?

thanks

Yes RideSteady will easily correct that and synch the engines’ speeds. But - you should be running higher rpm - closer to 7,400-7,600 range
7,050 rpm at WOT is low...
Assuming you are hitting the wire stops at the APS wheels inside engine compartment? - there is a @JetBoatPilot yutube vid for that adjustment
if very hot/humid air - that could explain it, too.

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[Ridesteady]

@C Spez Welcome to jetboaters.net! You're going to like it here.

Yes, Ridesteady will likely be able to correct the difference electronically when in use. But, per @swatski 's well-regarded advice, it's also best to check to make sure the throttle cables (which terminate to an "APS" sensor) are as well adjusted as they can be: https://jetboaters.net/threads/rpm-big-difference-twin-engines.5586/

I agree, 600 RPM seems like a lot if the cables are adjusted properly, and it's on two new engines. That said, the engines will have some difference throughout the RPM range naturally, even with perfectly adjusted cables, which is why it's nice to have electronic synchronization.

 

[Nate Fallow]

I have the same issue with my 212x ....not quite as pronounced as yours but annoying nonetheless.

 

[NorfolkJames]

Hello I am new to jet boating and new to this forum any suggestions are welcome.
I have a 2018 Yamaha AR240 I bought it new in July of this year, I had the 10 hr service done and boat does not have 50 hours yet.
Since day one the engines RPM have been different by over 500 RPMs and get progressively worse at higher speeds.
I brought it in immediately to the dealer who claims the throttles cables are adjusted properly, the lift gates are in line with each other and the pitch of the impellers is accurate, fuel lines are fine and air filters are clean,
but the issue of the RPMs continues.
Has anyone else experienced this too and is there a solution to getting both of the engines to run at the same RPMs without manually adjusting one throttle ahead of the other?

thank you

On my AR240 I just get up to speed, fiddle with the throttles until they are roughly sync'd and hit the cruise control button and then use it to control speed.

 

[Weeb]

This just started happening to me once in a while. The port will be off by 300-400 rpm even with the cruise on. I have to pull the throttles back to neutral in order to get them synced up again. I have had some condensation in the port tack since new and I‘m wondering if that has something to do with it.

 

[marcham]

Can you feel or hear the difference? Could it just be an instrument error? Have you tried swapping the wiring between the tacs?

 

[swatski]

There are analog tachs and also digital readout in the Connext. But yeah, I guess the sensor could be off...?

 

[Weeb]

i wasn’t able to hear any difference but I’m half deaf from playing my guitar to loud for years. the Second time I was actually trying to see if I could hear a difference because the steering wasn’t pushing one way. I would think at +400 rpm I would hear it but it was busy around me so I was trying to get clear enough to stop and go again without causing issues with other boaters. I need to go out and see if it happens again and pay more attention to everything.

 

[JWExperience]

I just fiddled with the throttle cable screws in the engine bay at the end of my first summer to get them around 100 rpm of each other at my typical cruising speed. WOT was close enough as rare as it is for me to go that speed. My port was almost an inch or two ahead of starboard to be close to the same rpm. I think I watched a jet boat pilot video on YouTube to get started.

 

[Weeb]

I just fiddled with the throttle cable screws in the engine bay at the end of my first summer to get them around 100 rpm of each other at my typical cruising speed. WOT was close enough as rare as it is for me to go that speed. My port was almost an inch or two ahead of starboard to be close to the same rpm. I think I watched a jet boat pilot video on YouTube to get started.

I did that when I put in the JBP throttle sync. I went out yesterday it didn’t do it again.

 

[Offseason]

I am having RPM sync issues when I get over 3,000 RPM. The mis match is 500-1000 RPM lower on the port side engine.
When inspecting the APS i am slightly out of spec
APS 1 = .93 kohm closed and 4.67 Kohm open (out of spec)
spec range is .5-.9 Kohm closed and 3.75-4.35 Kohm open
APS 2 = .8 closed and 4.45 open (with in spec)
spec range is .35-1.05 closed and 3.6-4.5 open

could the APS 1 being slightly out of spec cause this?

 

[swatski]

I am having RPM sync issues when I get over 3,000 RPM. The mis match is 500-1000 RPM lower on the port side engine.
When inspecting the APS i am slightly out of spec
APS 1 = .93 kohm closed and 4.67 Kohm open (out of spec)
spec range is .5-.9 Kohm closed and 3.75-4.35 Kohm open
APS 2 = .8 closed and 4.45 open (with in spec)
spec range is .35-1.05 closed and 3.6-4.5 open

could the APS 1 being slightly out of spec cause this?

I couldn't help adjudicate those voltage differences, but having a mismatch between the twin RPMs in mid range is not unusual. Are your engines close at WOT?

There is a limit to what you can achieve trying to adjust the mechanical linkages to match the RPM. I gave up at some point, the only thing is to slightly split the throttles.
BUT
The permanent, and in my opinion nearly perfect, solution is available - @Ridesteady system. It is incredible. It provides electronic synchronisation of the engines RPM, you will never have to think about it again.

My other boat has the newest and greatest electronic fly-by-wire Yamaha F300 outboard, I still prefer my mechanical 240 1.8 with Ridesteady cruise control - that's how good R-S is. (in my opinion). There is a couple good threads on this topic to read here on the forum, and R-S customer support and response time is second to none.

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[Billtex2000]

https://jetboaters.net/threads/rpm-big-difference-twin-engines.5586/

 

[Offseason]

I couldn't help adjudicate those voltage differences, but having a mismatch between the twin RPMs in mid range is not unusual. Are your engines close at WOT?

There is a limit to what you can achieve trying to adjust the mechanical linkages to match the RPM. I gave up at some point, the only thing is to slightly split the throttles.
BUT
The permanent, and in my opinion nearly perfect, solution is available - @Ridesteady system. It is incredible. It provides electronic synchronisation of the engines RPM, you will never have to think about it again.

My other boat has the newest and greatest electronic fly-by-wire Yamaha F300 outboard, I still prefer my mechanical 240 1.8 with Ridesteady cruise control - that's how good R-S is. (in my opinion). There is a couple good threads on this topic to read here on the forum, and R-S customer support and response time is second to none.

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I was hesitant to try WOT because of the louder noise coming from the Port engine, I have had this boat for 3 seasons and the RPM is usually within 100 or so. having it jump to a 1000 rpm difference has me concerned. the previous owner installed a throttle sync product that locks the throttle levers together.

Thanks for the recommendation on the ridesteady product, I did not know about that previously