Correctly installing upper and lower oil seals on a 1998 Yamaha C115TLRW

[Soundear]

Hello all! I hope everybody is doing well. I have a problem that hopefully someone can help me with. In 2014, I purchased a 1998 Yamaha C115 with a boat. The motor looked real clean. Before I attempted to run it for the season, I decided to service the components on an outboard that one expects to eventually fail; spark plugs, thermostats, gas / water separator, inline gas filters, new gas lines, new primer bulb and of course, the Water Pump. Upon removing the water pump housing and lower plate, I saw quite a bit of rust on the driveshaft bearing cap where the oil seals sit. I also noticed the lower Unit gear case housing dripping a bit of oil from the propellor shaft carrier bearing housing where the lower seals sit. I removed the oil plugs to discover the oil was milky white - an indication that there was water intrusion. I purchased upper and lower OEM seals (2 up top and two on the bottom) as well as the Yamaha service manual for that motor. I removed the old seals with the correct tool to not score the seat walls, cleaned everything up so no burrs were evident, found a truck socket that fit the outer circumference of the seals, and pressed the new seals in so they bottomed out. The upper seals with both open sides facing upward to the drive shaft splines which contacts the powerhead; and the lower seals with both facing outward toward propellor nut. I have a very small compressor with a regulator; rigged up my oil oil pump line and connector directly to my compressor and carefully regulated the air between 7 and 10 lbs to listen for leaks. It held pressure, so I buttoned it up and ran it. After my second trip, I decided to take a peak at the oil to verify it was in fact black and not mixed again with water. I had a little bit of clear water come out and again.... milky oil! I retraced my steps and could not determine why water was still intruding - especially after my (not so pro) pressure test. I suspected maybe a defective seal - or most probably user error, as I somehow slipped or ****ed a seal crooked. I decided to do all four seals once again. Finally, it's 2016 all tested out as I expected so I ran it.

*2017 - 2018 - replace entire water pump - no evidence of water in lower unit, changed oil, new crush washers
*2018 - 2019 - replaced impeller - no evidence of water in lower unit, changed oil, new crush washers
*2019 - 2020 - Ready to replace impeller, change lower unit oil and crush washers when.............

Last week, I proceeded to drop my lower unit oil to replace and a good pint of clear water drained hard from the casing! I was shocked! Upon benching the lower unit, I did my pressure test to hear both the upper and lower seals leaking; the Lower carrier bearing seals hissing consistently; the upper bearing seals were expelling air louder as I pressed sideways slightly on the drive shaft. I'm the first to admit I am not a professional mechanic by any stretch....... but this kind of maintenance procedure is something I presume I can do correctly as it seems not very difficult to achieve with the correct tools, literature and patience to do correctly.

Questions:
* With what I've explained above, does anyone see anything I may be doing wrong to have such poor success replacing these oil seals to have them work correctly as designed? If not, any suggestions?
* I mistakingly dropped the woodruff key in the exhaust area of the lower unit. Is this a concern with respect to it interacting with anything in the motor that can create another problem?
* Is it imperative I use "Hypoid Oil" as the service manual indicates - or is 90 weight Lower Unit "Yamalube" oil also suitable these days for Hypoid Gear applications?

Thanks for your time!!

[panasonic]

You never mentioned the condition of the driveshaft and propshaft where the seals run. Any pitting, wear???

Also how much side movement of the driveshaft are speaking of? Do you have any side to side movement in the propshaft?

[Soundear]

No pitting or noticeable play in either driveshaft. I too thought something on the driveshafts had to be tearing up the seal, but can't find any reason why!. I put slight thumb pressure sideways on the driveshaft to hear a change in the air escaping with no noticeable play or even evidence that I'm pushing on it.... otherwise I'd suspect the bearing if there was any play! I'm reluctant to just change the seals again as I feel I'm overlooking something. Any ideas?

[panasonic]

Strange problem for sure. Are you putting some water proof grease on the lips of the seals when you installed them? And a little grease on the shafts where the seals run?

[Soundear]

Yes, and I'm using a little "Yamalube" grease on the seal lip and shaft for what it's worth! (its expensive!)
I have just a few questions for you if you don't mind:

* For some reason, I'm having a difficult time removing the upper seal driveshaft cap...is that typical?
* Open ends of both seals on uppers and lowers should face out to sea water correct?
* Should I be concerned with my woodruff key dropping in the exhaust area of the LU?
* What's your take on "Hypoid" oil.... do you suggest I use that exclusively as the service manual suggests?

Thank you so much for sharing your professional knowledge with me!!

[panasonic]

I don't mine at all. First off I am not a professional outboard mechanic, most on here are not. I am a aircraft mechanic.

I am not sure of your exact engine set up and I don't have the manual for it so I am not sure what you are calling the driveshaft cap. I do know the seal carrier can be stuck with corrosion and takes much prying to get it out, sometimes it gets destroyed. Search for other posts about that.

Open ends of the seals face out on Yamahas.Other manufacturers have them back to back. It shows that clearly in your service manual I highly suspect.

I would think shaking the crap of the LU that the key would fall out..But it will be blown out with the exhaust and water soon enough and I cannot see how it would harm anything.

The hypoid gear oil topic has been debated many times here before, with many different opinions. I generally stay out of those debates. I will say though you generally can't go wrong with what the manufacturer recommends.

I honestly don't know why you are having so much trouble with those seals..and without being there to see with my own eyes it hard to give good advice.

Does this engine have many hours on it?

I know it would bug the crap out of me if I changed them and then had to do it again in just a few years.

[Soundear]

Thanks for the response! I guess I mean the upper bearing cap or cover that sits under the water pump. The service manual indicates the seals go on after the cap, so I really don't need to take it off. I bought the boat with engine in 2014. If the cleanliness of the motor itself tells a tale, I'd say it wasn't used as much as other 1998's. I live in Florida and use the boat almost every week and run it on an average for 1-1.5 hours per weekend. I put 300-400 hours on it myself since 2014. Thanks for all the suggestions..... I guess I'll just take it real slow; inspect everything, clean it up, check for ridges or burrs on the driveshaft and prop shaft, change the shift seal and O ring, pressure test it and hope for the best!

[99yam40]

I would drain the gear lube and pressure test with soap and water mix looking for bubbles to see where the problem is before replacing things.
putting grease in-between the seals will help keep the spring on the inside seal from sitting in water if the outside one lets some thru

[Soundear]

Thank you for some great advice! When I removed the bearing housing (the one that sits under the water pump plate) the two shins that were on top of the thrust bearing were torn up. The bearings look clean, no nicks. Could that have been the issue? The service manual doesn’t indicate if the shims should go up or down - I would imagine it matters because because they seem to be cupped!

[99yam40]

I know nothing about those shims, but to think they were tore up means something had to be spinning them around maybe to cause that

[Soundear]

So.......After looking closer, I discovered the tore up debris could't be remnants of shims, but instead could very well be the outer edge concentric of the Thrust bearing casing itself which seems to have somehow peeled off ! I cleaned up the bearing area of any other small debris. Although this bearing looks and feels good, it probably needs to be replaced. It's quite expensive...as a good price is $160! Unlike a "typical" bearing that's self encapsulated, this thrust bearing is sold in two pieces. It has a relatively small frame that holds the roller bearings and a washer like disk that one side rides on. With the bearing housing removed from the driveshaft, I decided to turn the lower unit upside-down so I could access the prop shaft seals to replace and inspect the lower bearing hoping not to find any other debris. As I flipped it, I heard something hit the floor and quickly realized it was the thrust bearing. It surprised me as I assumed it was pressed on the driveshaft and not just floating. I need to read the service manual to determine what's normal and review proceedure for replacement. I just thought to give this description of my discovery with some pics to see if anyone has seen anything like this before and can offer any opinions as to why it happened.

[Soundear]

Just a quick thank you to all that responded to me and offered suggestions to my problem! I believe one of the prior owners of the motor years ago took the upper thrust bearing cover off and reassembled the shims iNSIDE the thrust bearing! Unlike most closed bearings which are encased, the Thrust Bearing is "open" with a washer like cover that sits on top of it. Shims are to be placed on top of that washer - not under it. I believes shortly after the ball bearings made pasta strips out of the once circular shims, the space it created resulted in excessive play in the drive shaft which in turn beat up my seals!! For safety sake, I replaced the Thrust Bearing as well as the upper & lower seals and shift seals! I just thought to share my solution in hopes of saving someone in a similar situation a major headache!

[99yam40]

well it sounds like you got it all back together and running well.
thanks for letting us know

[pstephens46]

Did he buy a service manual at
some point?

[Soundear]

Well.... Update #2..... I pressure tested my new seal job a few months ago before putting oil in. The pressure held (10lbs for 5 mins)
I decided to wrap it up. I filled my lower unit with oil and put the lower unit back on the motor. I ran the motor the first day (1/2hr) to see if I found water in my oil. I lifted my motor, removed the lower oil fill screw to find clean oil only. It seemed like victory!
Just today, I took the propeller off to put another one on and noticed the “petroleum rainbow” in the water an indicator of either a fuel or oil leak. Upon taking the prop off, I noticed a puddle of what looked like fresh oil collected in the lower unit housing on top of the bearing carrier! I’m stumped!

I’m trying to think of what is causing these seals to blow. I did notice something I’d like to ask the experienced mechanics out there:

1- I noticed for the first time that my exhaust gasket was missing: (the rubber cupped almost hexagon looking gasket
that fits into the recess valley behind the water pump.)Even at idle, I did notice water being forced from the seam between the engine cowl where it bolts on to the midsection while facing the motor in the right side. The water pump indicator mounted on the left side was shooting a stream harder than I noticed it’s been in the past.
*Is it possible water was somehow pushed in to the lower unit because the gasket was missing?

2- I have no problem bringing it to a certified mechanic, I’ve replaced the Upper and lower seals, water pump, Thrust bearing with shim. It’s been quite a challenge to find a solution to my lower unit seal problem.
*Does anyone suggest I measure the spaces between gears and verify shim sizes? I’m noticing absolutely no play when grabbing either the Propellor Driveshaft or main driveshaft and trying to push it laterally. The lower unit makes no noise at any time when running. Only upon inspection do I notice my lower unit is dripping petroleum when I lift it after a day out
*Is it possible that a very small amount of play is enough to create my problem?

3- I had been reading online other people’s experiences and decided to see the performance difference if I changed my 13 1/4”x 17” Propellor to a 13”x19”. My idea flopped as I lost a lot of speed and the motor seemed to be working harder. I ran it for about 1 hour. It’s Only because today I wanted to change back to the original prop that I discovered oil pooled on top of the lower unit bearing carrier. I didn't think this “prop change experiment” should have in any way created a breach in the lower unit prop bearing seals... .....right?

I estimate about 20hrs on the engine since my previous overhaul. I’m going to take off the lower unit now; empty the oil out, then pressure test with soap and water. I’m almost positive the lower seals are blown.... I’m curious to see how the uppers held up

Does anyone have any other ideas on how to get to the root of my issue?

thanks...