Yamaha100 HP making noise at low idle - VIDEO

[jb_wi]

New to me boat with 100 HP Yamaha 4 stroke (Year 2000). It's making a clattering sound while in gear, only at low idle.

Here is a cold start video..gave it a few minutes to warm up.

At about 2:10 into the video you can hear what I'm talking about when I put it into gear.

At about 3:30 I gave it just a little throttle, and the noise goes away.

Any idea what this noise is?

https://www.youtube.com/watch?v=TiDfV0ip7SQ

[cyber16]

to me it sounds like the gears are not meshing, do you normally just slam it into gear @ idle as should be done or have you been easing it into gear that you should not do?
Dog clutch may need some work.

edit: I don't recall since my last yamaha 150 was many years ago but does the yamaha also have gear/threads on the prop shaft to drive a lower oil pump like some outboards?
I suggest you get the motor into the shop before severe damage happens
It could be something as simple as a worn thrust washer front or rear that needs replacement, I did have to replace one many years ago on my Yamaha. For me it was a diy project.

[MarkG]

This is called prop rattle or prop chatter.

Very common with 4 strokes. Not a problem,just an annoyance when on muffs out of the water. You probably won't even notice in the water. There have been discussions here on how to minimize or eliminate,with various prop options, etc. I myself never bothered. I did notice that a THICK coating of grease on my propshaft and proper prop nut torque seemed to quiet it down a bit when on muffs, but I don't hear it when on the water.

Do a search forum on prop rattle, you should find more info,or even a google search, there's plenty talk about it. Or just hold tight, you will likely get some advice on the issue right here.

[cyber16]

Mark are you sure? I have heard prop rattle, but never like that.
https://www.youtube.com/watch?v=_apbx1egUpI

maybe its just his is more consistent and not as intermittent sounding?

I agree I am sure others that have dealt with prop rattle will chime in at some point

[jb_wi]

It's also pretty pronounced when on the water. That's what drew my attention to it. I've only had the boat for a few weeks and I didn't notice it on the test drive when I rode in it with the original owner, but now after having it out on the water a few times it's really buggin me.

I may take it in to get a new impeller, just because I don't know when that was last changed, and I can have the tech check out the prop rattle while it's there.

Here's the sound while on the water.

https://www.youtube.com/watch?v=hvEixyBH6QM

[jb_wi]

Also - thanks for the replies. Been reading through the forum and it looks like a Flo Torq III, or IV hub will significantly reduce the chatter.

I'll have to research exactly which one I need and may order one up and give it a shot.

[jb_wi]

A little more info on what I'm finding in the forum. It sounds like the majority of four stroke prop chatter issues were related to the use of heavier stainless props. I was a little confused since mine has the factory (year 2000) prop on it, which I assumed would be aluminum. Well, just went and pulled it off to get a closer look and to examine the hub, and found out that this motor came with a steel prop. It's painted black from factory, so not sure if it's factory stainless or what, but it's definitely steel..since a magnet does stick to it.

It looks like it has a rubber hub, so I'm not sure if I can remove that myself or not, but I would like to replace the hub with the Flo Torq IV, or just buy a new prop with a Flo Torq hub, and keep this original prop for a spare.

Will keep this post updated with what I find..all I know is, I won't be able to live with this prop chatter unless I absolutely have to.

[jrdonicht]

Hub cannot be replaced with a flo-torq That is a Yamaha black ss prop with a pressed in hub [It should also be much heavier than aluminum] And yes they give you terrible prop rattle at idle[it will shake the whole boat at idle in gear]. If you want to know for sure try a Aluminum prop and put it on. I had to buy a ss prop with the flo-torq hub insert and yes the flo-torque III did the trick You could also take the prop off put the muffs on and put it in gear like your video then you would know if its excessive gear lash

[cyber16]

I suppose you could remove the prop and see if the sound is still there.
Not sure if the weigh of the prop on the shaft makes a difference if it is not prop rattle.
But if the sound IS still there, then you know for sure its not..?

[jb_wi]

Thanks for the great info. (yep, the prop is very heavy)

Kinda sucks that I need to buy a prop, but I'm also relieved that I don't have any major issues going on. I'll order a different prop in the next few days and post an updated video when it's installed. I will keep the SS Black for a spare or sell it depending on what they sell for these days.

-JB