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  1. #1

    Default BF225A4 - Whining Noise Primarily at Idle

    All,

    One of my 225s makes a whining noise primarily at idle, or low RPM. At higher RPM, the noise gets quieter or just gets overcome by the engine noise. I can't hear it at all at cruise. I used a stethoscope to try to find the source, and it sounded like it was at the gearcase/mid-shaft bushing. I removed the mid-shaft bushing (which was new anyway), but the sound persisted. Lower unit oil is also new and looks fine. It has done this to some extent since I bought the boat earlier this year, but I think it used to be intermittent/quieter, or, as I've used it more, it has just become more annoying. I'm not really sure.

    Here is a video of the sound. Anyone experienced this before/have any idea what is causing it?

    Last edited by wildebeest; 07-16-2021 at 10:37 AM.

  2. #2

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Also, in my google searches I found a guy who had a similar problem on a mercury lower unit (video below), but he never resolved the issue and has just lived with the noise for 3 years now. I know he changed all the bearings in the lower unit without resolving the issue too.

    My first thought after the mid-shaft bushing didn't fix my 225 was that it was the bearings in the lower unit, but I'm hesitant to change them all out since it looks like a colossal pain if it's not going to resolve the issue (like it didn't resolve the issue on this guy's mercury). The sound gets muffled when I'm actually on the water and the lower unit is totally submerged, more like this video with the mercury, so it's not quite as loud as in my video in the trash can, but it's still pretty loud.


  3. #3

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    I guess it could also be a belt/pulley bearing, but would that sound transmit into the driveshaft to make it sound like the noise was coming from the driveshaft/mid-section where the noise seems to be the loudest?

    It really seems like the sound is coming from the drive-shaft/mid-section more than the lower unit or engine.

  4. #4
    Join Date
    Sep 2008
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    Hague, Virginia, USA
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    I hear the noise, but cannot identify where it is coming from.

    You need to get a stethoscope with a probe end and pinpoint the noise. Be sure to check the timing belt and alternator belt rollers and cams with the silencer case off. Check the alternator shaft bearing, too.
    CHawk 25 DLX

  5. #5

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Quote Originally Posted by chawk_man View Post
    I hear the noise, but cannot identify where it is coming from.

    You need to get a stethoscope with a probe end and pinpoint the noise. Be sure to check the timing belt and alternator belt rollers and cams with the silencer case off. Check the alternator shaft bearing, too.
    Well, I scoured that engine today with a screwdriver/stethoscope while in the trash can trying to nail down the source of the sound. It's not any of the pulleys or the alternator. From the top, it clearly sounds as if it coming from below the engine, but it does reverberate through the block. From the top, it actually sounded loudest on the alternator, but I pulled the belt off the alternator and ran the engine on just the battery and it still made the noise, so not the alternator or alternator shaft bearing.

    The source of the sound has got to be the drive shaft or lower unit. The sound is loudest on the mid-section, but I can't really listen to the actual lower unit that well while it's running in the trash can.

    I'm kind of thinking it is either a bearing in the lower unit or the thrust bearing on the drive shaft. If it's the thrust bearing, I guess I'll just run it until it explodes.

    However, I likely did screw up my tensioner. It looked pretty rough with corrosion so I pulled it off, but it seemed to rotate fine without any noise (also didn't make noise when running). But when I reinstalled it and "loosely tighten[ed] the timing belt tensioner bolt" per the manual, the belt was far too loose and flapped around. I manually tightened it with pressure from my hand, but I understand that I shouldn't have to do so and there has got to be a procedure other than "seems tight enough with pressure from my hand" (although that's how I've always done automotive belts). I'm planning to get a new tensioner in any event since this one is so corroded. Any advice on reinstalling it other than the vague "loosely tighten" it statement in the manual and getting it to tension properly?

  6. #6
    Join Date
    Sep 2010
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Can you use a broomstick to listen to the lower unit while it is in the trashcan.------I am sure that would work the same as a screwdriver.

  7. #7
    Join Date
    Apr 2018
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    1,571

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Is this a counter rotator, if so this noise is common, insufficient preload on the forward gear, ignore it or reshim the bearing. Just a crap design

  8. #8

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    I'll check if this is the counter-rotating lower. I think this is the standard rotation (it's on the starboard side) and the port side is counter-rotating, but I'll confirm.

    And I found the procedure for adjusting the timing belt tension at 3-23 in the manual.

  9. #9

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    This is the standard rotation lower.

  10. #10
    Join Date
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Check the mid-shaft bearing again. And DO NOT let it run until it fails completely - it can eat a hole in the forward part of you lower cowling.

    BTW - what is the year or SN of your 225. At about mid-2007 Honda revised the lower cowling so that more lubricating water could get to that mid-shaft bearing, which fixed most of the failures. Somewhere around SN 1500500, I think.
    CHawk 25 DLX

  11. #11

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    I'm SN 1200000-something so I have the older version of the lower cowling, but I have the mid-shaft bearing completely removed and still get the sound. The video is with no mid-shaft bearing installed, but it makes the noise whether I have the bearing in there or not. That was my first thought since the bearing was previously destroyed and had galled up the drive shaft a little bit where the bearing goes. I thought perhaps the imperfections in the drive shaft rubbing against the bearing were making the noise, but apparently not.

  12. #12

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    So this may be related to some areas where the paint appears to be melting off the lower unit.

    There are two lines on both sides of the lower unit where the paint has come off. These were originally just on one side and I assumed the paint had just been worn or scraped off. But the same set of lines recently came up on the other side of this lower unit.

    It looks to me like bearings are getting hot and melting the paint on the gear case, but after pulling the prop off and looking, there aren't any bearings underneath these areas. This is essentially in the hollow part at the prop shaft holder before right before the main gears in the lower unit. And I would assume any bearings here wouldn't spin unless the prop shaft was spinning so wouldn't be causing my whining noise in neutral. I also checked the external temperatures after running and it seemed to be around the same temperature as the other lower unit and essentially the same as the water temperature. Anyone know if this is a sign of a mechanical issue--which I suspect it is--or just a cosmetic issue?

    Click image for larger version. 

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    Last edited by wildebeest; 08-04-2021 at 12:18 PM.

  13. #13
    Join Date
    Sep 2008
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    There most certainly are bearings in that part of the lower unit. That appears to be where the main bearing holder is located.

    See pages 12-19 through 12-26 in the shop manual.

    Copy is here: http://planbmarine.com/wp-content/up...BF200A-BF2.pdf
    CHawk 25 DLX

  14. #14

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Thanks. The larger mark toward the front is slightly behind where the prop shaft holder meets the gear case--so right behind the main bearing and maybe an inch away. And I guess the mark toward the back of the unit is close to the needle bearing. But there is a space between each of these bearings inside the prop shaft holder and the gear case that should have water in it when submerged. The space filled with water when submerged is what is directly behind these apparently heat affected areas. There has got to be hella heat coming off these bearings to heat up the gear case--especially when it's basically transmitting that heat through water. And it must cool down extremely quickly after the load comes off of it to show a normal temperature as soon as I lift the engine out of the water.

    I'll probably just break down and rebuild the lower and replace all the bearings and seals, then. This looks to be a colossal pain from the manual where I'll need some special tools I don't have, but I'll give it a shot.

  15. #15
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    When/if you get into it, I suspect you may see that the bearing carrier and/or cover has come apart. But just speculating about that. I don't have any first hand experience tearing down that lower unit. Hopefully, someone on this forum can offer some good advice.

    If I were in your shoes, I would consider trying to find a re-built lower unit.
    CHawk 25 DLX

  16. #16
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    Apr 2018
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Those lines are caused by someone heating the gearcase in order to remove the bearing carrier and not bothered to repaint it. That does not come from mechanically generated heat. It is possible the unit has been overhauled and not shimmed correctly. This is not a job you can do unless you have the special tools for shim selection.

  17. #17

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Quote Originally Posted by iang6766 View Post
    Those lines are caused by someone heating the gearcase in order to remove the bearing carrier and not bothered to repaint it. That does not come from mechanically generated heat. It is possible the unit has been overhauled and not shimmed correctly. This is not a job you can do unless you have the special tools for shim selection.
    Ahh, that makes perfect sense. And they may have shot a coat of paint on it badly without adequate prep and it has been wearing off over time (I never looked that closely at the lower unit paint job)--that's why the marks were initially visible on only one side and why they've all become more apparent with more paint wearing off over time.

    So could the potential improper shimming cause the whine with no load?

    Any harm in continuing to run it like this for the rest of the year? I've already run it 50+ hours with the whine (gotta catch those fish).

    Would a Honda dealer be able to re-shim this properly for me, or with the cost, should I just look for a new or rebuilt lower?

  18. #18
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Quite honestly, if there is no metal on the magnetic drain plug, I would just carry on using it as normal. These gearcases are not expensive to rebuild but it us essential to shum them correctly. Anything amiss will definitely result in metallic flakes in the gear oil. Hope this helps

  19. #19
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Ian - good catch. I would never have thought of that. Thank you for your continued participation in and contributions to this Forum.
    CHawk 25 DLX

  20. #20

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    This is my last crazy question for this thread. I'm looking at some used or new lower units to get away from the whine, but as final confirmation that it is the lower unit making the noise before I get a different lower (though I'm 90% sure it is the lower), I want to test without a lower to see if it makes the noise.

    Is there any harm in pulling the lower unit and running the motor without a lower unit and with no water for about 5-7 seconds to see if the whine is still there with no lower?

    I would imagine it is like a jet ski and can run without water for 10-15 seconds without issue, but is there anything crucial in the lower unit/drive shaft to the actual engine? I've heard some older Yamaha 4-strokes ran the oil pump off the drive shaft, but I don't think that is the case here.

    Obviously, the safer option is probably to swap my good, counter-rotating lower onto this motor for the test in a trash can, but that changes the job from removing and reinstalling one lower one time to removing and reinstalling lowers three times.

  21. #21
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    Apr 2018
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    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Firstly, you can't just swop lowers, the shift shaft splines are different. You could leave the shift shaft out just to try.You can run the motor dry for about half a minute, it will not hurt it, more than that might burn the exhaust seals, not a good idea.

  22. #22

    Default Re: BF225A4 - Whining Noise Primarily at Idle

    Thanks!

    You guys are the best!

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