Problem solved! It was the prop. Filed down the cupping on the trailing edge slightly and the noise is gone. What happened was last summer I broke part of a blade off and replaced the prop with a different aftermarket brand, same pitch. These are aluminum. Didn’t use boat until late fall when I noticed the noise. Didn’t associate it with the new prop since I hadn’t used it for several months. Started researching and everything said driveshaft bushing.

Clarence Chapman sorry to hijack your thread. If you’ve replaced your prop lately maybe that is it.

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I’ve been reading a lot of posts of propellers causing whine or ringing. I have a sneaky feeling it may be that. Last year I replaced a broken prop with an aftermarket one. Didn’t use boat for a couple months. Noise might have started after that. Anyway I’m going to put the original Yamaha prop back on and see if that’s it.

Here’s the diagram for the lower unit and water pump.

https://www.simyamaha.com/parts/use-parts-diagrams-to-order-parts?year=28&model=1758&category=49

You’re thinking of the seal that is under the water pump. The driveshaft bushing is actually about 6-8 inches up in the mid section. After you remove the lower unit you can look up in there and see it. It has a snap ring holding it in but mine was stuck in there and had to cut it out. It’s a brass ring with a rubber sleeve. Item 23 in this parts diagram.

https://www.simyamaha.com/parts/use-parts-diagrams-to-order-parts?year=28&model=1758&category=13

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OK for some reason this site locked me out and couldn’t reset password so I’m back as trwhit57. I put my boat in the water and ran it for 15 minutes or so. The noise was present right off the bat at same rpm range. One thing I noted is that if you turn the motor all the way left or right the noise goes away but comes back as soon as motor is straightened out.

I had a Yamaha mechanic listen to the video and the first thing he said is driveshaft bushing needs grease, which I have already removed. Only other thing he could think of is maybe the metal cup in the water pump might be rubbing the driveshaft. Took that apart and it is not rubbing. At a loss for what to do now except just live with it.