Rumbling Noise from Outdrive

daman4469

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Feb 22, 2009
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Hi all! I have a 1988 dynasty Apollo with a merc 4.3 4bbl and alpha one Outdrive.
Let me start by saying I was negligent and did not change the lower unit oil last fall. This spring I did, and it was a milky color. It's since been changed. Took the boat to the lake today, and it ran ok while idling. Once we hit open water, I got in to the throttle a little and got up and purring around 50 mph. All was grand. Suddenly, I heard what sounded like a clunk (thought I snapped a belt) and then a rumbling sound ensued. Luckily, I wasn't too far from launch and made it back without issue.
This low rumble (whirring like a bad wheel bearing) was persistent, but I could get it to go away if I set the trim just right. Any movement from that sweet spot though, back it came. It would get a little louder the further down or up I adjusted the trim. Also, left and right steering increased the noise.
This happened whether in gear or not. My first instinct was a bad gimbal bearing. Given the nature of boat repair shops, I can't just 'find out what's wrong' without still forking over a good bit of labor cash. Before I take it, inthink the wife wants to know what we are getting in to, and I do too. If we figure a grand I don't want a 2000 dollar surprise.
I have read through some posts and seen that my symptoms mimic a bad gimbal in some cases, and bad u joints in others.
Any thoughts? Is this a project I can tackle myself with a decent amount of hand tools, or is this better off done at a shop?
 

Rick Stephens

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Yes. One or the other. With the way it came on probably ujoint. Takes ten minutes and minimal tools to pull a drive and see for yourself.
 

thumpar

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Pull the drive. It is going to have to come off anyway. The job is easy. You will have access to both the gimbal bearing and u-joints.
 

daman4469

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Feb 22, 2009
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Thanks guys for the quick replies. I'm mechanically inclined but this particular issue is new to me. I've seen my share of bad bearings and u joints, I assume they'd be the same on a boat. If I'm unsure, could I get some input by posting pics?
 

thumpar

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To pull the drive first put the throttle in forward. Remove the six nuts holding the drive to the bellhousing. Remove the trim ram pin that goes through the drive. You can then pull it off the boat.
 

daman4469

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Feb 22, 2009
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I appreciate all the help thus far. My heart absolutely sank after hearing that noise!
I will check it out myself. It's out of commission anyway, sounds relatively simple to diagnose, and worst case scenario I can take it somewhere. Thanks again you guys!
 

Rick Stephens

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Thanks guys for the quick replies. I'm mechanically inclined but this particular issue is new to me. I've seen my share of bad bearings and u joints, I assume they'd be the same on a boat. If I'm unsure, could I get some input by posting pics?

I just replaced the u-joints in my Alpha 1 and used regular ol Federal Mogul u-joints from the local NAPA store.

The Gimbal bearing is very simple check. Pull the drive, stick your fingers in and rotate the bearing. I'm betting u-joints though.

The one thing I have seen, or better yet heard, is if I have a leak and the u-joint bellows fills with water, the outdrive rumbles a lot. I assume because the CV joint acts like a blender with grease and oil in the jar. This also washes the grease out of the u-joints.

Pulling the outdrive is simple, fast and easy. And will quickly answer pretty much everything. And you definitely don't need a certified marine mechanic for these basic repairs. Pulling the drive and servicing it should be part of every boat owners repetoire. Lots of UTube videos showing how. And lots of expertise here to help.

Rick
 

daman4469

Petty Officer 2nd Class
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Feb 22, 2009
Messages
107
I just replaced the u-joints in my Alpha 1 and used regular ol Federal Mogul u-joints from the local NAPA store.

The Gimbal bearing is very simple check. Pull the drive, stick your fingers in and rotate the bearing. I'm betting u-joints though.

The one thing I have seen, or better yet heard, is if I have a leak and the u-joint bellows fills with water, the outdrive rumbles a lot. I assume because the CV joint acts like a blender with grease and oil in the jar. This also washes the grease out of the u-joints.

Pulling the outdrive is simple, fast and easy. And will quickly answer pretty much everything. And you definitely don't need a certified marine mechanic for these basic repairs. Pulling the drive and servicing it should be part of every boat owners repetoire. Lots of UTube videos showing how. And lots of expertise here to help.

Rick
Thanks for the encouragement. It really helps...
From what I've read elsewhere and here, it seems that water intrusion could be the cause of this, whether it's gimbal or UJ? If so, where should I be checking for entry? Is there a gasket or hose? The gimbal and UJ bellow is separate from the lower unit and its oil right?
I'm looking in my repair manual but the exploded views from 1988 aren't real clear...my young eyes are too used to HD!
 

Rick Stephens

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Water can intrude into the u-joint lots of places - the u-joint bellows is most dire since it can sink you - slowly, but effectively. The list of common places is u-joint bellows, lower shift shaft seal, drive to bell housing gasket, water port o-ring.The u-joint bellows and shift cavity areas are supposed to be dry with only air inside.

The drive has 4 oil seals that have water on one side and oil on the other, and one seal that has air on one side and oil on the other. The one with air is the input shaft seal right behind the CV joint at the top of the outdrive. Obvious what happens when a seal with water on one side leaks, you get oil going out and water coming in. But the input shaft seal behaves differently, it is not designed to keep water out, only to keep oil in. If the u-joint bellows gets full of water, usually you get water in the drive through that seal even though it would not leak oil.

If you have water in the u-joint bellows, usually the best procedure is to replace all bellows unless you can find something like a gasket that was leaking.
 

thumpar

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Water in the u-joint bellows will also cause rust on the input shaft and kind of grind on the seal making the leak worse.
 

daman4469

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Feb 22, 2009
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I will check those things. From what I am hearing, my bellows are okay since my bilge is usually empty at the end of the day....I suppose I will be able to tell pretty quickly whether or not water made its way in there.
As a note, I did have water in my lower unit after last season....enough to make it milky. I'll have to keep that in mind when checking these things.
 

daman4469

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Feb 22, 2009
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Water in the u-joint bellows will also cause rust on the input shaft and kind of grind on the seal making the leak worse.
Got the unit pulled today. Had a bear of a time. Turns out it pulled the gimble bearing out with the shaft. I guess that needs replaced. Water in bellows as well. U joints are rusty. Gimble has play in it. Attached some pics for your entertainment!
 

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Rick Stephens

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Those are all pretty easily handled by your own self. Good job! Getting a drive off with the gimbal stuck is a chore and a half.
 

daman4469

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Feb 22, 2009
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Thanks! It was a butt kickin and a half but my son and I got it!
I'll be ordering the replacement kit tomorrow and once it comes in I'll get the new U joints (they're ok I think but since I'm in there)....my only stump now is, how do I get that shift cable out of the gimbal housing? I see a brass nut in there but there's an aluminum shift piece in the way.
 
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thumpar

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There is a socket made to remove the cable. You still need to make sure you find out where the water came from. Bellows is usually the first place. How do the bellows and big oring look?
 

daman4469

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Feb 22, 2009
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O rings look okay.... What I like though is that the kit comes with all new o rings, gaskets, gimbal and bellows....It kind of looks to me that the bellow is separating from the transom side lip, but can't really tell....I'll know more once I buy the socket to remove the gimbal housing.....
Here's the kit I was looking at. Looks complete and looks as though it would cover all my bases....what do you think?
http://shop.nuwavemarine.com/transo...-kit-9a-108/?gclid=CJS6_e2ag80CFYsehgod6PECvA
 

daman4469

Petty Officer 2nd Class
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Feb 22, 2009
Messages
107
See that's why I'm here! Learning tricks i would never try.
I only had up to 3/8 torx.....largest Allen I have is 3/8 also so I'll snag one tomorrow (hoping they aren't too tight!)
I am hoping that kit will give me all that I need....
 
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