Notices
The Boating Forum

Water in lower units

Old 06-18-2020, 02:19 PM
  #1  
Junior Member
Thread Starter
 
Join Date: May 2020
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
Default Water in lower units

So I have trip 300 yamaha 2016 motors with 400 hours on them. Took them to a yamaha service center, said my starboard motor showed signs of water intrusion. He replaced the top seals. I put it in the water ran it about 4 hours and took the lower units off myself to inspect and to make sure it was just the top oil seal on that one motor. I had water in all three motors. I ran a pressure check and as I was pumping I could hear hissing and watched oil come out around my prop shaft on the motor that had the top seals replaced. The other two lower units I could hear the hissing sound and oil also came out and around the prop shaft. To my knowledge the seals on both the top and the lower have gone bad. Is this normal at 400 hours for all three lower unit seals both top and bottom to go bad?
Old 06-18-2020, 03:54 PM
  #2  
Senior Member
 
Join Date: Jan 2007
Location: NSW Australia
Posts: 7,880
Received 2,495 Likes on 1,404 Posts
Default

Fishing line doesn't care how many motors it gets caught around, especially braid, it will chew out a seal real quick, have you removed the props to check?
Old 06-18-2020, 03:59 PM
  #3  
Senior Member Admiral's Club Member
 
Join Date: Jul 2011
Location: Boca Raton
Posts: 2,840
Received 1,181 Likes on 647 Posts
Default

It can happen in just a couple hours. They do fail. You were wise to check. Common service item. Did the mechanic offer you any cause on the initial diagnosis?
Old 06-18-2020, 06:31 PM
  #4  
Junior Member
Thread Starter
 
Join Date: May 2020
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
Default

So the mechanic said he saw water in the starboard motor and figured it was the upper seals. So they replaced them. They didn't see any water in the center or port motor when they drained the lower unit so didn't do any pressure check on those motors. I used a simple bike hand pump with a gauge with a fitting at the bottom of the lower units and went to 12 PSI. On all three lowers I heard hissing sounds and watched residual oil (I drained them all before doing the pressure test) come out the bottom of the prop shaft. The gauge went down from 12psi to 10psi and seemed to hold steady from there. There was no fishing line as I don't fish on this boat, but I did take off all the props and didn't see any issues with fishing line.

So im wondering are these a yamaha 300 lowers (2016) a common issue or is there something I'm doing wrong here?
Old 06-18-2020, 06:34 PM
  #5  
Admirals Club Admiral's Club Member
 
Join Date: Dec 2003
Location: Westbrook, CT USA
Posts: 1,787
Received 381 Likes on 219 Posts
Default

Not a common issue, but you need new seals.
Old 06-18-2020, 06:54 PM
  #6  
Member
 
Join Date: Mar 2011
Location: San Diego, CA
Posts: 37
Received 9 Likes on 9 Posts
Default

Originally Posted by shaneJ View Post
So the mechanic said he saw water in the starboard motor and figured it was the upper seals. So they replaced them. They didn't see any water in the center or port motor when they drained the lower unit so didn't do any pressure check on those motors. I used a simple bike hand pump with a gauge with a fitting at the bottom of the lower units and went to 12 PSI. On all three lowers I heard hissing sounds and watched residual oil (I drained them all before doing the pressure test) come out the bottom of the prop shaft. The gauge went down from 12psi to 10psi and seemed to hold steady from there. There was no fishing line as I don't fish on this boat, but I did take off all the props and didn't see any issues with fishing line.

So im wondering are these a yamaha 300 lowers (2016) a common issue or is there something I'm doing wrong here?
If there's no smoking gun like fishing line then I doubt you could be doing anything to wear out seals that fast. Also, 10psi is probably good for a lower unit; they're not tires. If there wasn't any water intrusion in the other two you're probably fine. I'd check the gaskets or crush washers on the drain and fill screws first in any case (no pun intended) of water intrusion where you can't find an obvious point of entry. Those are easy, cheap, and should be replaced with every drain/fill anyway.
Old 06-18-2020, 07:06 PM
  #7  
Admirals Club Admiral's Club Member
 
Join Date: Aug 2013
Location: Fairhaven, MA
Posts: 10,049
Received 1,610 Likes on 979 Posts
Default

My go to Yamaha shop recommends replacing the driveshaft seals whenever the water pump is done. Seems like cheap insurance.
Old 06-18-2020, 09:54 PM
  #8  
Senior Member
 
Join Date: Nov 2016
Posts: 198
Received 90 Likes on 49 Posts
Default

Someone jump in here if Iím wrong but 12psi? I donít think you can expect it to hold near that much pressure.

Iíve had 5 sets of drive shaft seals fail including a brand new factory Honda 150 lower within 20 hours.

if youíre holding 10psi the issue could be a balance issue with the shaft. Maybe the seal is good but the shaft isnít true?
Old 06-19-2020, 04:38 AM
  #9  
Junior Member
Thread Starter
 
Join Date: May 2020
Posts: 5
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Sharktopus View Post
Someone jump in here if Iím wrong but 12psi? I donít think you can expect it to hold near that much pressure.

Iíve had 5 sets of drive shaft seals fail including a brand new factory Honda 150 lower within 20 hours.

if youíre holding 10psi the issue could be a balance issue with the shaft. Maybe the seal is good but the shaft isnít true?
I did a dial test on the prop shaft and it was with in limits. But I did realise when I did the pressure test it was from the drain/fill screw (bottom) and not the top vent screw.

Last edited by shaneJ; 06-19-2020 at 04:58 AM.
Old 06-19-2020, 04:52 AM
  #10  
Member
 
Join Date: May 2016
Posts: 34
Received 5 Likes on 3 Posts
Default

Firstly; Mechanic should have pressured tested the first one and not just assumed it was the top seal. In my opinion from the way he diagnosed the first gearbox I would not be surprised if there was possibly water in the other 2 when he drained them but not enough to cause concern in "his professional opinion". I have only ever changed them when they let go, never as a preventive maintenance measure. Replace them all and happy days.
Old 06-19-2020, 04:58 AM
  #11  
mbb
Senior Member
 
Join Date: Jan 2002
Location: State of confusion
Posts: 3,603
Received 1,199 Likes on 642 Posts
Default

Find a new mechanic.
It's usually the lower seals from fishing line as said, top seals rarely go bad by comparison.

it should have been pressure-tested to identify the leaking seal
And pressure tested after any work was complete.

Your mechanic is a POS.
Old 06-19-2020, 08:25 PM
  #12  
Member
 
Join Date: Mar 2011
Location: San Diego, CA
Posts: 37
Received 9 Likes on 9 Posts
Default

Originally Posted by Sharktopus View Post
Someone jump in here if Iím wrong but 12psi?
You're not wrong. My opinion of course. A positive pressure test is nice reassurance but it doesn't really represent much in the real world except maybe when the LU sits in the sun out of the water and gets really hot. I've cracked the vent screw more than once and gotten a face full of gear lube from the pressure. The ideal situation is good seals and more or less equal pressure inside and outside the gearcase.
Old 06-20-2020, 03:27 AM
  #13  
Senior Member
 
Join Date: May 2011
Posts: 1,410
Likes: 0
Received 63 Likes on 42 Posts
Default

Originally Posted by shaneJ View Post
On all three lowers I heard hissing sounds and watched residual oil (I drained them all before doing the pressure test) come out the bottom of the prop shaft.
to get oil to flow visibly past a seal the seal has to be completely shot. air flows past as visible bubbles(use soapy water), but oil is much much thicker . and if you got to hold at 10psi then you need to take another look at what you were seeing.
there is no way oil would flow at 12, but not at 10.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.