Throttle Drop - working as designed? True?

[JasonSchoenrock]

I finally got my 2016 LS back to my local dealer and one item on the list was for him to fix the port side throttle drop issue that's been there since the beginning (I'm familiar with the fix posted here but it's more than I wanted to handle as DIY). The dealer came back and said:

"My tech Just got off the phone With Tray from Yamaha and he sent him the forum you have sent me, Yamaha STATES that the port motor will drop up to 300 rpm, its designed to do that be casuse [SIC] there are two different pitch props on the boat. If they would run the same rpm it would pull to one side. I hope this helps."​

Is this true? Should I just let them run like that? I don't notice any pulling when I have the RPMs synced up manually. Any insight is appreciated!

 

[Neutron]

Same props on both pumps in your boat. Just look up part numbers. They should be the same

 

[OrangeTJ]

The impellers May be the same but the way the pumps load with water in relation to the impeller rotation is not. In my experience, a couple/few hundred rpm difference between engines at the same throttle setting is normal.

 

[swatski]

The port side is always a bit faster. 200-300 RPM (higher on PORT at WOT) would be normal.

The pre-2015 boats had impellers with different pitches, the PORT pitched more aggressively to compensate for unequal loading. PORT impellers were marked by notches on the impeller "neck", to distinguish from STRB. Starting with 2015 MY - boats with AK (articulating keel) - they stopped doing that.

One way to get the engines to spin closer together in their RPM rates is to install the Lucky 13 (L13) cones with more spacers on the PORT side.

Another is to bend the blades (DIY re-pitch), which is not too difficult on the trailing side.

@Ridesteady is the ultimate solutions, IMO, electronically synching and basically a fly-by-wire system. Best mod in my boat, use it every single time I go out, cruising (control RPM) or water sports (control GPS speed).

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[Julian]

amaha STATES that the port motor will drop up to 300 rpm, its designed to do that be casuse [SIC] there are two different pitch props on the boat.

Throttle tension is one of the areas many people have issues with on these boats. This statement sounds like a way to creatively get around their real issue - that the throttles don't stay when you put them (on some boats). Suggesting that the boat "automatically" drops RPM on one side to even out the thrust is hogwash (IMHO). The throttles should remain where you set them no matter what. If I want one engine running 500 rpm more because I'm in a cross wind, I don't want the boat "deciding" to even them out for me!

 

[Cobra Jet Steering LLC]

When I read the first post I was just shaking my head in disbelief. Years gone by they did use different pitched impellers, but not any more and yes the pumps do load differently due to not having counter rotating engines and the angle of the hull effecting one pump differently than the other . But really I wonder who was responsible for that story ? The mechanic or Yamaha.

 

[Julian]

But really I wonder who was responsible for that story ? The mechanic or Yamaha.

And IF it was Yamaha....was it some guy in a call center somewhere who's never touched a boat?

My bet is on a dealer mechanic that either doesn't know how to fix it, or can't be bothered to figure it out.

 

[JasonSchoenrock]

Thanks for the comments. I totally agree- the throttle should stay where I set it. The port side physically moves backward so I have to pull the starboard back to compensate to keep them in sync. I spend alot of time looking at my gauges to ensure they are in sync when I should be looking up at traffic or back at whoever I'm towing. @swatski I think my situation is the opposite of what you describe. The port side is lower RPM, plus my boat is a 2016, so should not have the issue at all, right?

Once I get them set and synced up, I generally use the +/- cruise buttons to adjust speed, so the issue is really just going from no-wake to cruising or towing speed/RPM.

 

[Cobra Jet Steering LLC]

Maybe it was the same author of the infamous "you did not install the cleanout plug correctly" explanation for plugs blowing out during use.

 

[Scottintexas]

If they would run the same rpm it would pull to one side. I hope this helps."

oh it helps, it helps us continue to lose trust in Yamaha corporate or their dealership network,

I think I've run plenty of times at the same rpm and not experienced any pulling, although I actually have a boat with different impeller pitch,

 

[JasonSchoenrock]

I've gone back and asked for the explanation in writing from Yamaha - so we'll see what they come back with.

 

[Julian]

All that said, I've never worried about RPMs being in sync and never focus on them. I drive by feel and shift on throttle forwards or back depending on conditions. That said...my new E-Series boat remains in single lever mode a LOT. But with my SX230, it was not something I worried about. Having a throttle slip though...that would be bothersome...getting them in sync....couldn't care less.

 

[Cobra Jet Steering LLC]

You are handing them a shovel ,

my bet is they say it was just a miscommunication and they will look into it.

 

[swatski]

@swatski I think my situation is the opposite of what you describe. The port side is lower RPM, plus my boat is a 2016, so should not have the issue at all, right?

Make sure your throttle cables are hitting the APS stops - particularly the PORT side - it may not. If it does not, that is (one part) of your issue!
THis may help:

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[swatski]

my new E-Series boat remains in single lever mode a LOT

That is the key! I think with MR1-HOs revving up to 10,000+ RPM a bit of a difference becomes less tangible, I find the 1.8s in the 5,000-7,000 RPM range to be quite intrusive when not running in synch.

This is an interesting phenomenon, certainly known in aviation!
A single propeller is not annoying. However, if there are two vibration sources that are not quite synchronized, we hear the difference between them. Therefore airplane propellers must be synchronized!

What is interesting is that our hearing/senses appear very sensitive to vibrations at lower frequencies and they can become mentally intrusive.

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[Julian]

That is the key! I think with MR1-HOs revving up to 10,000+ RPM a bit of a difference becomes less tangible, I find the 1.8s in the 5,000-7,000 RPM range to be quite intrusive when not running in synch.

This is an interesting phenomenon, certainly known in aviation!
A single propeller is not annoying. However, if there are two vibration sources that are not quite synchronized, we hear the difference between them. Therefore airplane propellers must be synchronized!

What is interesting is that our hearing/senses appear very sensitive to vibrations at lower frequencies and they can become mentally intrusive.

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Hey! There is a benefit to being brain dead!

 

[swatski]

Thanks for the comments. I totally agree- the throttle should stay where I set it. The port side physically moves backward so I have to pull the starboard back to compensate to keep them in sync. I spend alot of time looking at my gauges to ensure they are in sync when I should be looking up at traffic or back at whoever I'm towing. @swatski I think my situation is the opposite of what you describe. The port side is lower RPM, plus my boat is a 2016, so should not have the issue at all, right?

Once I get them set and synced up, I generally use the +/- cruise buttons to adjust speed, so the issue is really just going from no-wake to cruising or towing speed/RPM.

There is a couple good FAQs, too.
I find that when in rough water the throttle drop can happen whenever the boat hits the waves. Even with E-throttles - those can move (inadvertently) too as they are very smooth and move easily.
When running in rough water I tend to use the @Ridesteady now, and just push the throttles levers (binnacles) all the way up - that way they do not tend to move or drop much at all - while I adjust RPM/speed with the knob.

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