Yamaha complaint

I took delivery of a 2011 Yamaha 115 HP four stroke on a tidewater 180 CC with a 20 in. transom in March of 2011. I have a complaint. The problem is that the motor vibratation at idle speed, is so bad until everything inside the boat shakes. Above 1100 RPM its ok. Both the dealer and Yamaha did their best to correct it but could not. Finaly they told me that the problerm was harmonics, that is the motor and the boat are not in harmony and nothing can be done about it.

I accepted that explanation until I learned that in May of 2011 Yamaha came out with a new and improved 115 HP four stroke. To me this indicates that they knew there was a problem with the old 115 HP four stroke. I begged them to swap with me for the new version, but they refused. In other words the suckers who bought the old 115 HP four stroke and have problems can suck air.

I believe Yamaha makes great motors 99% of the time and will buy another one but when they turn out an ourboard with a problem that cannot be fixed, they refuse to acknowledge it and will dig in their heels rather do whats right just to save money. I am the loser. I am very disapointed in Yamaha management. The next outboard I buy will be well tested before I accept it.

Re: Yamaha complaint

This post should be moved to Yamaha motors forum. I have a 03 carbed F90 on a 18 alum. Johnboat and it is smooooth at idle and anywhere else on the rpms, once it warms up alittle. I cannot believe the "harmonics" theory, sounds more like an engine balancer problem, But I'm no expert. I believe some of the motors have balance shafts? that cancel this type of shaking? I'd be beyond mad about this if they will not/cannot correct it.

Re: Yamaha complaint

What in the world possessed you to post this in the Trailers and Towing Forum, Bones??

I also think there is a problem with your engine, not with Yamaha's design.

Re: Yamaha complaint

JB said:

What in the world possessed you to post this in the Trailers and Towing Forum, Bones??

I also think there is a problem with your engine, not with Yamaha's design.

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I agree. I have a pair of F115's...manufactured in 02/02...and they are not known for an idle issue problem. All the newer Yamahas are being made lighter and more efficient..but there are no major changes to the original design of the F115's. You need to find another dealer who is a little more willing to properly diagnose the problem...

Re: Yamaha complaint

Billy Bones said:

To me this indicates that they knew there was a problem with the old 115 HP four stroke. I begged them to swap with me for the new version, but they refused. .

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I don't think there is a problem with your motor as much as their is problem with the people working on it. What did "Yamaha" actually do. If it is a rigging problem it is the dealers responsiblity.

Re: Yamaha complaint

I have a 2006 F90, which if you look at the specifications, doesn't appear to be all that different. From day one I noticed a vibration in the boat at idle when the engine is trimmed all of the way down. It much less if I trim the engine up just a bit (and make sure that it is not down all the way against the stop). Also, the vibration will go away above 1,000 RPM. This is something that I neither like nor was expecting, but it's not a really big issue for me either.

Is this a good engine? You bet. And it runs like a sewing machine.

Re: Yamaha complaint

I have experienced this.
Motor and boat were fine.
Moved motor to a different boat and it rattled the boat to pieces.

Resonant frequency.

If the motor produces vibration at a frequency that matches the resonant frequency of the boat, the boat will shake.


"In physics, resonance is the tendency of a system to oscillate at maximum amplitude at certain frequencies, known as the system's resonance frequencies (or resonant frequencies). At these frequencies, even small periodic driving forces can produce large amplitude vibrations."

Like Woodnaut says, try trimming out a little.

You may be able to change the resonant frequency of the boat with modifications to the transom, I don't know, maybe some bracing or reinforcing.

I would think this is a boat problem more than a motor problem.

I have also seen this in motorcycles.
At certain rpm's, the hand grips will buzz like a vibrator.

Re: Yamaha complaint

I have a question , is the vibration in or out or gear ,while sorting out the correct pitch on my pontoon, I put on a new prop and had a instant vibration. And had the same issues while running of course I Knew exactly what it was and it was a brand new prop. And the prop was ok it just didn't work well with the boat motor combo. it may be some thing that simple. I would try it without any prop or change it out and see if it is still there. A prop can still be turning a small amount even out of gear and changing props will change harmonics. Just a thought. You may of all ready tried changing props.

Re: Yamaha complaint

I looked at Tidewaters website. Curiously all the 18ccs are shown w F90s in all the pics I saw. perhaps the 115 is alittle large for that model? I say this having purchased my used 1860 jon w the max. rated hp w an F90 and have since realized this heavy motor is a bit much for it. The 2 stroke 90s are lighter and the weight is lower on the transome compared to the inline 4cyl F motor, I do enjoy the extra power, it's fast,fun and very responsive for a jonboat. But the topheavy motor makes the boat rock more when wakes hit broadside at rest, or when overcoming them from behind another boat at speed more so than a lighter engine w a lower center of gravity would IMO, but I'm no expert. Also if I slow to stop quickly, like when I see something ahead in the water, my wake will come over the transome as the heavy motor makes the boat squat down and the large wake it creates hits the stern. Perhaps you could contact other Tidewater 18/F115 owners to find out I they experience the same vibrations at idle? Also, Does this boat have hydaullic steering? that might transmit more vibs also. As for the prop swap advice, Solas has a new hub design, Rubex, that they claim allows up to 10'/.percent give or flex between the prop and shaft. I have one on my F90, 4bld alum. and it is smoother and shifts quieter/softer than the old fact. Yamaha prop. Maybe that could solve or lessen your vibration problem? Though it would'nt help while idleing in neutral.

Re: Yamaha complaint

I was on my son's 19' Sea Hunt with a 115HP Yamaha 4 stroke just yesterday, and it's so smooth and quiet, it's hard to imagine all the vibration you're describing. Maybe remove and inspect prop for debris wrapped around prop shaft, damaged blades, loose prop nut, bent prop shaft, whatever might cause this vibration. Maybe try a different prop?

Re: Yamaha complaint

If it's in gear doing it, I'd suspect the prop first and the prop shaft second.