15 Yammy Weird Noise

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dgram36

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I dropped my 1989 15hp Yamaha off to get serviced/checked out before duck season. The guy replaced the prop, changed the lower gear oil and replaced a few fuel lines. He also cleared a small blockage by applying some reverse air pressure on the weep hole. When I received it back he said that it ran like a top and he was correct. I took it out for the first time today and it's running very strong. The only thing that I noticed is a weird whining noise around mid throttle that sounds a lot like a bad fan belt in a car. I can't tell if the motor drowns it out at full throttle or if it goes away. After hearing the noise I was kind of hesitant to run the motor much because I thought something may be wrong. Take a look at this video and If you guys have any insight as to what could be wrong that would be much appreciated.

https://youtu.be/SaWYgFUr2jM
 
hwew said:
Did you check the gear oil.
I opened the top bleed screw and stuck a piece of straw in to see if it was full and it appeared to be. I will drain it completely tomorrow and check for any metal.
 
I drained the gear oil this morning and it was in fact full, and there was no metal or water in the oil. Any other ideas?
 
The gear oil could be a different viscosity from what was in the gear case before it was serviced.

My guess is it could be gear clash noise or a bearing in the lower gear case or on the crankshaft. You mentioned that the prop was changed. I would start investigating there. Does the new prop spin freely without binding when the engine is in neutral. Does it make noise when you push on the exhaust/hub when spinning.

Pull the prop off and look for wear marks. It could be a bad fitting prop. While the prop is off check the propshaft. Make sure it is straight. A bent propshaft can bind bearings.
 
I put the same viscosity gear oil back in it after draining and it's still making the noise. Prop seems to fit just fine and spin freely in neutral. I will tear it down this week and inspect the lower unit just to make sure nothing is wearing abnormally. Thanks for the tips.
 
if its nothing obvious like what Trip or Dale said, take it back to the guy and show him the vid
 
I would check it with the cowl off to make sure there isn't any fuel leaks. A fuel suction leak will cause a whining noise as air enters the fuel system. Your mechanic replaced fuel lines and the best place to start troubleshooting a problem is the last thing someone touched.

I highly doubt it's the lower unit unless a bearing is going bad. I suppose it would be possible to tighten the prop nut too much and the prop could be binding against the lower unit housing but that's a stretch at best
 
sonny.barile said:
Did you figure out what it was?
Not yet, haven't had time to look at it. Called the guy who did the work and asked him to listen to the video. He said he would and then never called back so I will try to do what I can to fix it on my own or find a new mechanic to take a look. When I figure it out I'll let you guys know.
 

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