# Oil on cavitation plate!?!?



## nathar (Jun 25, 2009)

So, I'm getting the boat ready to take out tomorrow morning, and I notice a small puddle of oil on the top of the cavitation plate. There was a drop or two on the bottom side. It wasn't thick and stringy like gear lube. Rather, it had the consistency of engine oil. I checked the oil drain plug on the back of the motor, but it was dry. Engine oil level was right at the top of the hash marks.

I'm perplexed. Where could this oil have come from? Tomorrow morning I'll check the gear oil in the lower unit to make sure there's no water in it. If there is, it's going to piss me off because the previous owner and I split the cost of an annual maintenance service, which included removing the foot, replacing the water pump impeller and changing the gear oil.

What do you think? It's a 2005 Yamaha F115. That's water beading on the oil film, btw.


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## doradohunter (Aug 8, 2010)

Oil spilled from changing the oil. It's probably fine.


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## nathar (Jun 25, 2009)

doradohunter said:


> Oil spilled from changing the oil. It's probably fine.


No, sorry. That service was performed a couple months ago and I've been out twice since then (that's a damned shame, but the weather has been sucky for that long).

This is brand new.


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## BlueWaterWarrior (May 28, 2015)

Maybe you ran through a light oil slick in the marina or at the ramp?


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## BlueWaterWarrior (May 28, 2015)

I'm assuming you have already pulled the engine Cowl off and had a look around in there?


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## Five Prongs Of Fury (Apr 15, 2008)

Check inside around lower cowling. Valve cover gasket would be my suspect. I've have this same issue on a F90.


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## hjorgan (Sep 30, 2007)

Also check your tilt/trim pump. Had a seal blow on one of mine, and it created an oily foot


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## markw4321 (Oct 4, 2007)

I run twin f115s most likely sad to say,it is lower unit oil. I had oil on the cavitation plate awhile back and it was from the lower unit. As I recall the top fill plug is just above the leading edge of the cavitation plate. Good luck,with it.


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## nathar (Jun 25, 2009)

hjorgan said:


> Also check your tilt/trim pump. Had a seal blow on one of mine, and it created an oily foot


This may be a eureka moment. I've noticed that the trim pump is making some pretty weird noises. I'll check that in the morning. Thanks.


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## nathar (Jun 25, 2009)

markw4321 said:


> I run twin f115s most likely sad to say,it is lower unit oil. I had oil on the cavitation plate awhile back and it was from the lower unit. As I recall the top fill plug is just above the leading edge of the cavitation plate. Good luck,with it.


Mmmmm, I think the top plug is actually below the cavitation plate. I'll look in the morning. I'm suspecting the trim pump because it started making strange noises.

This is all coming together. I repaired the forward trim switch one day. That's the switch that allows you to raise and lower motor while you're up front. I always trim the motor all the way up so that I can tuck the cowling up under the cover. One morning, I walked out there and noticed that the motor was all the way down. Confused the hell out of me because I knew that the day before it was up.

So I was wondering if some big ass cat or raccoon sat down on that forward trim switch and let the trim motor run until some seal broke. I think the noise would have scared an animal away, so I'm suspecting a supernatural being. I highly doubt it's a human. Boat is in the back yard under a boat shelter. It's wierd. :001_huh:


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## nathar (Jun 25, 2009)

Five Prongs Of Fury said:


> Check inside around lower cowling. Valve cover gasket would be my suspect. I've have this same issue on a F90.


Squeaky clean.


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## markw4321 (Oct 4, 2007)

http://www.thehulltruth.com/boating...oil-leaking-upper-weep-hole-help-see-pic.html

Above link is to a case of oil leaking from an F150. Should be same lower unit as f115. Note the top drain fill plug location. Check for residual oil that could have been come from the top weep holes and run down along the top of the cavitation,plate while underway. Good luck with it.


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## nathar (Jun 25, 2009)

Mark, you were right. In my mind's eye, I was seeing the fin above the weep hole thinking this was the cavitation plate.

However, I found some oil on the fin above the weep hole, and on the cavitation plate. No oil coming from the weep hole, and no oil drips coming from the lower cowling (I think that's what it's called).


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## markw4321 (Oct 4, 2007)

Nathan

Not sure where it is coming from given the oil on the top of the fin above the cavitation plate. I would still check the lower unit just in case and to rule it out
Good luck with it.


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## nathar (Jun 25, 2009)

Dammit! I was so looking forward to going out into the sound today just to get on the water. Catching fish would be a bonus.

I guess this could have happened between the time I purchased the boat and now (about three months ago). I've only taken it out twice.  The previous owner and I split the cost of an annual maintenance service. Certainly the mechanic would have said something if he drained out milky oil. I wasn't there for the service, but I trust the previous owner. I think he would have paid for a reseal had he known about it.

I wonder if it is possible to force water into the lower unit by using too much water pressure on the muffs? And if so, would that permanently damage the seals? Should I refill the lower unit and monitor the oil? Pull the foot and take it to a Yamaha mechanic and get it re-sealed? 

I replaced all the seals on my old Mercruiser Alpha One outdrive myself (except for the prop shaft seal that needed an expensive special tool). I also made a pressure tester afterwards that worked great and validated my handiwork. I may just suck it up and let a shop do it.


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## MrFish (Aug 21, 2009)

Have you taken the prop off and checked the seal? See if there's any fishing line there.


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## markw4321 (Oct 4, 2007)

nathar said:


> Dammit! I was so looking forward to going out into the sound today just to get on the water. Catching fish would be a bonus.
> 
> I guess this could have happened between the time I purchased the boat and now (about three months ago). I've only taken it out twice.  The previous owner and I split the cost of an annual maintenance service. Certainly the mechanic would have said something if he drained out milky oil. I wasn't there for the service, but I trust the previous owner. I think he would have paid for a reseal had he known about it.
> 
> ...


Just saw the picture with the water in the oil...

May want to disregard below....



I would clean the areas where you are seeing oil. Check the lower unit oil and if water is present Drain the lower unit. Replace the o rings on the oil fill / drain plugs. Then go fishing. When I got back I would check the areas I had cleaned to see if I could better determine where the leak is coming from. 


As long as there is some oil in the lower unit yamaha lower units are not known for failing due to a little water intrusion for a trip or two. That's been my experience anyway.


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## Kim (Aug 5, 2008)

You seem like a handy kind of guy, pull the propeller and look for oil that leaked out around the seal.


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## nathar (Jun 25, 2009)

Kim said:


> You seem like a handy kind of guy, pull the propeller and look for oil that leaked out around the seal.


I suspect the upper shaft seal or the shift shaft seal given where the oil was coming from and accumulating.


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## Kim (Aug 5, 2008)

It's a boat so there will always be something that you need to do.


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## nathar (Jun 25, 2009)

Ugh! Today would have been a good day to be on the water. Thought I'd just lube 'er up and go, but my Quicksilver gear lube pump wouldn't fit. Duh. SAE vs. metric. So I went ahead and dropped the lower unit.

The shift shaft seal looks good. No signs of recent gear lube.



Prop shaft seal looks okay, too.



Down below the water pump there appears to be gear lube. These two seals are easy to replace.





I still wonder if it's possible to force water into the lower unit with the muffs if the water pressure is too high. I'll pressure test it tomorrow to see if I can find a leak.


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## markw4321 (Oct 4, 2007)

On your question I have never heard of water pressure causing a seal failure. There are plenty of places for water to flow out of the engine to relieve hose pressure.


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## nathar (Jun 25, 2009)

I think it's missing part number 40, the oil seal cover.







Is this significant?


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## Chapman5011 (Mar 7, 2013)

Dont trust everything someone says about a boat that's for sale. 
They are selling a boat...


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## Chapman5011 (Mar 7, 2013)

That's a lot of water in the oil for two fishing trips.


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## Chapman5011 (Mar 7, 2013)

I see where you coming from, but he was selling a boat. 
Regardless of the situation,
I believe you are well on your way to repairing the issue. 

Hope to see good pics soon of your next fishing trip. 

Good luck. I know it's nerve recking, but you'll be on the water soon


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## nathar (Jun 25, 2009)

Chapman5011 said:


> That's a lot of water in the oil for two fishing trips.


So, I'm suspecting that the mechanic who did the annual service either didn't bother with changing gear oil (and billing us for it), or he didn't say anything (didn't give a shit).

This is why I always do my own mechanical work.


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## Starlifter (Feb 24, 2011)

Do you have a hand vacuum pump to test the lower? Also when changing the gear oil, do you always replace the flat o-ring seals that are behind the lower's fill and drain screws?


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## nathar (Jun 25, 2009)

Chapman5011 said:


> I see where you coming from, but he was selling a boat.


I think I've heard somewhere that all boat sellers are freakin' liars.  

No, I'll give him the benefit of the doubt. Otherwise, my worldview will go to hell in a hand basket.


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## nathar (Jun 25, 2009)

Starlifter said:


> Do you have a hand vacuum pump to test the lower? Also when changing the gear oil, do you always replace the flat of-ring seals that are behind the lower's fill and drain screws?


This is a new-to-me boat, so this is the first time I've had to drop the lower unit. If the service manual says to replace, I replace.

Do I need to pull a vacuum on the lower unit, or pump it up? When I resealed my Mercruiser Alpha One, the springs of all the oil seals faced toward the gear oil, and the leak detection procedure called for pressurizing the LU to about 10 psi and leave it sit overnight.

I noticed with this Yamaha, the springs face the water, exactly opposite from the Mercruiser. So, is this why you're proposing that I pull a vacuum?

My understanding is that these spring-type seals are designed so the spring-side faces whichever side of the seal has the greater pressure.

But yes, of course, I do have a hand vacuum pump. :tongue_smilie:


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## Big Red (Oct 1, 2007)

I think I would suspect the mechanic rather than the previous owner; the owner didn’t do the work.
& it damn sure wouldn’t be the first time even a good mechanic got in a hurry & screwed up & forgot a small part or two.


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## Chapman5011 (Mar 7, 2013)

By owning a boat, you get to learn things you never thought you would learn to do. 
I have had to learn to repair and rig all kinds of stuff by owning boats. 

It's so satisfying when you repair something yourself. 
I usually always try to do my repairs. Worst thing I have to do is call shane livingston to fix my repair.


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## Starlifter (Feb 24, 2011)

nathar said:


> This is a new-to-me boat, so this is the first time I've had to drop the lower unit. If the service manual says to replace, I replace.
> 
> Do I need to pull a vacuum on the lower unit, or pump it up? When I resealed my Mercruiser Alpha One, the springs of all the oil seals faced toward the gear oil, and the leak detection procedure called for pressurizing the LU to about 10 psi and leave it sit overnight.
> 
> ...


I looked in my Yamaha F150 factory service manual, and for the F150TXR it says to screw in a hand pressure/vacuum pump into the fill hole and pressurize it to 10 p.s.i.

I don't know if the check pressures differ between the F115 and F150; the service manual does warn to not over-pressurize or seal damage could result.


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## markw4321 (Oct 4, 2007)

http://www.pensacolafishingforum.com/f23/lower-unit-home-pressure-leak-test-471241/


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## nathar (Jun 25, 2009)

Just as I suspected. Drive shaft seals. Prop shaft seal and shift shaft seal were air tight.


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## nathar (Jun 25, 2009)

There's no big mystery about why it was leaking. Seal surface is rusty and pitted.


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## nathar (Jun 25, 2009)

Does anyone know if they make a repair sleeve specifically for this application? I've found a Speedi-sleeve that will work, but I'd have to install two of them. Not a big deal. I had to use two similarly on the camshaft seal on my old Mercruiser 470 which had two seals separating the crankcase from the cooling system.


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## Kim (Aug 5, 2008)

It may not be as bad as you think. Clean that up and get the crud off it to see how much the seals wore the shaft and how much pitting if any is in the shaft. a lot of mechanics clean it up and if the surfaces above and below the grooves are smooth the will set the seal a little higher or lower to get a good seal. I'm just not sure how much wiggle room you have with that assembly. Can't hurt to check it out. Other options, electroplate/machine the shaft, sleeve the shaft or buy a new one.


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## nathar (Jun 25, 2009)

Kim said:


> It may not be as bad as you think. Clean that up and get the crud off it to see how much the seals wore the shaft and how much pitting if any is in the shaft. a lot of mechanics clean it up and if the surfaces above and below the grooves are smooth the will set the seal a little higher or lower to get a good seal. I'm just not sure how much wiggle room you have with that assembly. Can't hurt to check it out. Other options, electroplate/machine the shaft, sleeve the shaft or buy a new one.


I had to do the same thing with the short yoke shaft seal going into the top gear box of my old Alpha One out drive. You would not believe the level of grief I got on the iboats forum for re-positioning the seals a couple of millimeters so that the lips were riding on a clean spot. Lots of derision, snide comments, and dire warnings about my out drive blowing up. Couldn't make them understand that it was okay to do. Four years later I resurrected the old thread just to inform the hysterical ones that all was still good (because they sarcastically told me to let them know when it blew up). 

"Oh, you got lucky" was their response. 

I think a Speedi-sleeve would be easier, though.


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## Sequoiha (Sep 28, 2007)

If you can find one a speedy sleeve would work well, just make sure you use a good coat of lock tite behind it.


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## nathar (Jun 25, 2009)

Sequoiha said:


> If you can find one a speedy sleeve would work well, just make sure you use a good coat of lock tite behind it.


I found a size that will work, will just need two of them because they aren't very tall.


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## nathar (Jun 25, 2009)

Motion Industries didn't have the Speedi-sleeves in stock, so I decided to try to polish the seal counterfaces. I used fine emory paper and oil, a whole lot of elbow grease and patience. After doing all I could with the emory paper, I polished with my Dremel flexible shaft attachment, polishing wheels, and rouge. It feels pretty smooth to the touch. I have limited experience with seal surfaces, but based on how well others like this have performed for me, I think it'll be okay.

Who agrees with me?





There appears to be some sort of plating on the shaft seal surface that's partially gone, but there's a band of smooth homogeneous metal (for lack of a better term) at the top and the bottom where the seal lips should ride. My trick is to color the shaft seal surface with black permanent marker, assemble everything using the old seals to get a reference point, then position the new seals, ensuring that they're on a good spot.


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## Kim (Aug 5, 2008)

I'm not an outboard guy but it looks to me like that's a sleeve pressed onto the shaft for the oil seals. I looked up the parts breakdown online and it didn't show a sleeve with the shaft assembly.


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## nathar (Jun 25, 2009)

Kim said:


> I'm not an outboard guy but it looks to me like that's a sleeve pressed onto the shaft for the oil seals. I looked up the parts breakdown online and it didn't show a sleeve with the shaft assembly.


Yeah, I didn't see one either.


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## nathar (Jun 25, 2009)

I removed the prop shaft seals this afternoon. I just drilled a 1/16" hole in the metal part of the seal, inserted a screw, and pulled it out with pliers. I was careful about not letting any metal shards get inside and also about not touching the shaft with the bit. They both came out really easily. Inner seal was in backwards. Prop shaft is pretty smooth with only a very slight groove visible. I'll try to seat the two new seals in a different spot.


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## nathar (Jun 25, 2009)

I also chucked the shift shaft up in my drill press and polished the minor groove with fine emory cloth, then P320, P600 sandpaper, and finally polished with maroon Scotchbrite pad. It's almost like new.

I'll get my parts delivered Friday, hopefully. I called my local Yamaha shop and asked if they had the seals in stock. She said she'd call me back in an hour. Never heard back from her, so I ordered from boats.net. I'm willing to pay more to support a local business, but not if you blow me off. :thumbdown:


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## nathar (Jun 25, 2009)

I installed all the seals in about a half hour, hooked up my pressure gauge, and pumped it up to just over 10 psi. The factory service manual specifies that it should hold 10 psi for at least 10 minutes. So far, it has held steady for two hours.

The gauge is the type used by plumbers to pressure test natural gas lines. It has a built in valve stem that is really convenient to use.



Initial pressure



Pressure after two hours



I'll call it sealed.


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## Stoker1 (Feb 17, 2014)

I'll give you a ring if my seal ever goes out.


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## AndyS (Nov 22, 2011)

Not really helpful to the topic of this thread .... but oil on the cavitation plate (and a lot of other places) is pretty normal for my 94 Merc. 

She always starts and runs though.
I call her "Old Smokey" !


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