Does this sound normal to you? (Yamaha lower unit)

Discussion in 'Boating Discussion' started by Baja Belk, Aug 14, 2019.

  1. Baja Belk

    Baja Belk Long, grandiloquent fish stories. Sorry.

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    Granted, I'm customarily pretty paranoid, but, historically, when I hear the slightest little noice in my truck or wife's car or whatever, usually ends up being something legit.

    Been noticing last few trips when flushing my F115 ('03, 1100 hours, serviced in February) a faint but sharp metallic grinding noise down by the prop shaft while running the motor in neutral. I use the flush hose attachment, no ear muffs. Usually let it go for 5 minutes with the motor off and then turn it on for a few minutes also.

    Additionally, when spinning the prop by hand clockwise, it makes a ticking noise. No play though. When spun the other direction it is smooth and noise-free.

    The other afternoon I made a quick kelp run and after dodging some stringers at speed on the way in, I thought the boat was running sluggish and the motor was steaming just a tad. Probably was temporarily wrapped and got slightly warm, but not hot enough to throw an alarm. Got the paranoia train rolling though.

    Did a couple other quick bay trips and the boat runs great at speed, but seems to be "growling" a little bit at idle.

    Pulled the boat out last night (was borrowing a slip that is now re-occupied by owner), and was flushing the motor at South Shores on the way home, and decided to throw it in gear for giggles. Sounded like a jar of marbles was loose inside the housing and I panicked, but after some quick research, it sounds like this is normal when not under load (clutch gear and driveshaft bouncing up and down).

    Back to my primary concern, the grinding noise down by the prop shaft. Got some good audio of it (was dark, can't really see much).



    Adding to my dilemma is the fact I'm flying out of town straight after work today, and won't even see the boat again until Sunday. Was trying to get out on Monday, so if I pull the drain plug and find gear chunks on Sunday when I return, I'm pretty much screwed without any time for a contingency plan.

    So what do you think? Paranoid? Or legit problem I should have a mobile mechanic look at while I'm gone?

    Thanks.....
     
  2. cortezpirasea

    cortezpirasea Pangero

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    I hear it too. Worries me.:o
     
  3. DoubletroubleII

    DoubletroubleII Fish On!

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    Maybe pull the prop and check for line wrap?
     
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  4. SeaHawk IV

    SeaHawk IV Well-Known "Member"

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    That doesn't sound normal to me either.
     
  5. sueno

    sueno Go Fishing!

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    Oh no that doesn’t sound good! I think the gears might be ready to go out completely! I would check the lower unit oil and see how much metal is on the magnet on the drain plug! Also check to see if any water had gotten into the lower unit!
     
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  6. sueno

    sueno Go Fishing!

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    Let me know if you need any help this week or the weekend! My mechanic is available! And half of the shop rates!
     
  7. Baja Belk

    Baja Belk Long, grandiloquent fish stories. Sorry.

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    No line on prop, noise is coming from further back. Sounds metal on metal.

    Fingers crossed is just low on gear lube. Unfortunately I realized late last night in the dark that I have a problem I need to address, and I'm currently stuck at work.

    If it's prop shaft or pinion, how bad is that repair? Just hoping there is some middle ground repairs vs replacing the whole unit.
     
  8. sueno

    sueno Go Fishing!

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    Good time to upgrade to a new Yamaha!
     
  9. Baja Belk

    Baja Belk Long, grandiloquent fish stories. Sorry.

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    Who do I look like, Billy K??
     
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  10. Baja Belk

    Baja Belk Long, grandiloquent fish stories. Sorry.

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    If I need a whole new unit, I'm gonna have to switch to my kayak for a few months......
     
  11. sueno

    sueno Go Fishing!

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    Or you could go budget with one of those Chinese lower units with the unconditional three-year warranty

    https://www.sterndrive.cc/
     
  12. slydawg

    slydawg Always wishin' I was fishin'

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    Not sure you should be running the engine with the flush hose, per my mechanic.
     
  13. dwaynesda

    dwaynesda dwayne

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    Mine did the same thing when I had a stainless prop on it. I took the advice of the mechanic and put the stock aluminum prop back on and it cured the problem. He said it is a common problem with those smaller, lower units on the Yamahas when switching to stainless props.
     
  14. Derby

    Derby My "Member" is Well Known.

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    How does the impeller get water on the flush hose? Pretty sure you need muffs if you want to run the motor. Pretty damn sure! Probably just your water pump that needs a rebuild.

    That was the sound of idle, out of gear or in gear.


    The gear shaft is always turning. Putting it in gear, FWD or REV, just moves the dog on to the main gear. If that was in neutral it could be as simple as the impeller housing rubbing on the shaft.

    Part 26 rubbing on 46.
    Yamaha115.jpg
    [​IMG]

    You could drain to look for milk or metal. Use a magnet inside a rubber glove and drain over magnet.

    If no issue, pull lower unit and rebuild water pump. If you pull it and inspect, your going to have to replace gaskets so you might as well rebuild.

    Running hot could point to impeller as well.

    What does it sound like in gear at idle?

    Oh, and screw the mobile mechanic...buy a Factory Service Manual for your exact motor. They are super easy to follow. It will save you thousands of dollars down the line. Rebuilding a water pump is as easy as rebuilding and Avet reel. Just a little bit bigger pieces.
     
    Last edited: Aug 15, 2019
  15. sbsurfer

    sbsurfer I've posted enough I should edit this section

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    You might want to check your impeller and water pump. If you're using the flushport to rinse out the motor you're not supposed to run the motor. Only run it with muffs on or submerged.
     
  16. openclass

    openclass Grand Master

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    I'm going to 2nd "good chance it's the water pump". The impeller is a thick piece of beefy rubber that sits inside of a stainless cup in a plastic housing. If you don't have water flowing through it properly, and you don't with the garden hose attachment, can you imagine the friction and subsequent heat being generated. There is an outstanding chance your water pump is roasted. Pull the lower unit and hopefully it's not something deeper than the pump.
     
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  17. Baja Belk

    Baja Belk Long, grandiloquent fish stories. Sorry.

    Location:
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    Mike
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    Just now circling back to this, some really good info here, thanks. I've always ran the flush hose with the motor off for 5+ minutes, and then turned the motor on to idle for a few minutes, which was based on mixed opinions from mechanics and other outboard guys. Sounds like that has not been the way to go. I also used a different mechanic this year for the annual service in February, and they did not replace the impeller (citing a recommendation from Yamaha to replace every 200 hours, not 100 hours - I also didn't know this until after I picked the boat up). I'm probably closer to 200 now so I'm feeling overdue. They did send a mobile mechanic after my original post who confirmed that the gear oil color and levels are good, and that the sound is most likely the "driveshaft rubbing on a bushing". I am going to try and replace the impeller this weekend or next week, and see if that makes the sound go away. Mechanic said I'm probably good for a few more trips before pulling the lower, but rather be safe than sorry.

    I'm not intimidated by doing the impeller myself, as long as the driveshaft bushing and woodruff key aren't seized.

    Thanks again for all the great advice, especially the parts breakdown from Derby.
     
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  18. acefuture

    acefuture Member

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    Let us know if/when you get this remedied. I have a similar sound on my F40 and after the countless hours I've spent on the interwebs to figure it out, i've narrowed it down to the stainless prop. I just did an impeller change and the noise did not go away. But if I take the prop off, there's no noise. The prop is heavy enough that with no back pressure the dogs rattle against each other at low revs in gear but once it gets to about 1k there's enough spin that the dogs don't have any play and the noise goes away. May have to go back to an aluminum prop to prevent premature wear.
     

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