Suddenly, It's really hard to shift into Reverse on my 1998 Yamaha C115 2 Cycle

[Soundear]

Yes... I was the one who had the constant water leaks oil my LU. I finally determined I was not tightening down the castle nut that holds the LU carrier in tight enough. I was thinking the double seals on the top under the pump kept failing or the double seals behind the prop when in fact after a careful pressure test I found the air escaping behind the LU boot carrier. Water was finding it's way around the big "O" ring seal behind the carrier. After I bought a nice spanner wrench to tighten it down good, I was quite happy to drop the oil yesterday to find absolutely not a drop of water!
Last season's water pump changeout alerted me that the exhaust muffler/ gasket was missing - or fell off when I pulled the LU one of the times I serviced it. I bought one on Boats.net ($13!) and found it very difficult to press the gasket up on the exhaust port in the mid section and not have it fall before re-attaching the LU. It appears to simply press on as the odd shaped gasket has a cupped opening on one side of it. No matter how I tried to press it on, it did not sit on the ridge correctly as it kept popping off! Maybe it wasn't a good idea to use just a bead of contact cement to hold it upside-down on the exhaust ridge until I bolt the LU in place thinking the LU exhaust side would sandwich it in place correctly. Apparently, it didn't, and blew out the hub exhaust and got caught up behind the castle nut at the prop exhaust port. My makeshift approach seemed like a reasonable idea at the time. My Seloc, Clymer and Yamaha service manual all mention no specific procedure but to simply place the exhaust "Muffler" on the port before bolting up the LU. Since that happened to me, i'm unsure about how to install it correctly so I don't fall into the same scenereo having it blow off again. The odd thing I see is the exhaust port shape in the mid section that appears to accept the muffler gasket shape is a different shape than the exhaust port opening behind the water pump on the LU it marries to when it's bolted together. It appears that it could easily slip off into the larger exhaust valley in the LU during operation. Weird!

When I found that gasket twisted up behind the prop, I thought just maybe that was the cause for my knocking sound. I put the prop back on and ran it without re-installing the exhaust muffler only to hear the same knocking sound surface again. I have a snake camera I'm going to use to inspect the cylinder walls with to see if I see any scoring on the walls or metal particles on the piston head. Next I'll put a garden hose on the water intake port to the powerhead and start the motor once again without the LU to listen for my knock to determine if it's in the Powerhead - and use your "Stethoscope" approach to narrowing down the specific location - or the lower unit to determine my problem

I respect your experience and thank you for your suggestions!

[99yam40]

I am at a loss as to what gasket you are talking about, because there is no exhaust gasket involved with dropping and installing the lower unit

[Soundear]

I only realized I even had a Gasket, Muffler missing when I helped my son in May change a water pump in a 1993 115 Johnson Outboard. On his motor, the muffler is placed on top of the exhaust port located in the LU. Just place the gasket on top of the exhaust ridge prior to bolting up the LU. After I saw his, I went to Boats.net and looked to see if my motor has a similar exhaust port gasket and found the Gasket, Muffler 6E5-45123. Prior to this parts search this past May, I never recalled ever seeing a gasket on my Yamaha whenever I serviced it. Sometimes these pencil drawings are not so precise, but from what I see the gasket is at the bottom of the exhaust port of the upper casing. Please advise if I'm misreading it
(In my previous message, I stated it cost $13 - wrong - it was $33!!)

[99yam40]

well apparently I have never pulled a motor apart far enough to find the exhaust manifold and muffler where this gasket would be located.
dropping the lower unit on Yamahas or Johnson/Evinrude's never did need replacing that gasket that I knew of

[TownsendsFJR1300]

For others; https://www.boats.net/catalog/yamaha...w/upper-casing

That muffler should not be coming out with the LU (or I'm misunderstanding something)..

Please clarify that it does, when the LU is removed...

What does part #29 go up against (the bottom of it(the top, of course, is obvious from the picture)?

Capture.JPG

[Soundear]

The only way into the upper casing to the exhaust housing is from underneath after the LU is removed. If you look up into it, the exhaust cast is molded in the shape of the gasket / Muffler. I would imagine if the gasket / Muffler fit tight that it should stay in the upper casing when removing the LU for seasonal servicing. Like I mentioned, I did not recall seeing that gasket as I removed my LU quite a few times. Since I do not have an elevator lift, I do my LU disassembly / assembly while standing in the water. It's quite possible during one of my LU removals that it unknowingly fell into the water because it presses on from beneath and has the potential to fall if not fully seated. After removal, I'll bring the LU to my workbench for service. Only after my kid dropped the LU on his Johnson 115 did I even inquire about my Yamaha having one. His is shaped differently and is mounted on top of his LU, but in essence is the same basic size and thickness. On my Yamaha, it's mounted out of sight inside the upper casing so unless you knew it exists, it's easy to overlook. It's a 5+" rubber gasket about 3/8" wide with a molded valley that is designed to "grab" the exhaust opening to seal it to the final exhaust port section in the LU. I can't keep mine from falling! I don't know how essential it is, but a "gasket / Muffler" sounds like it may quiet the motor down, and being it's a 2 Cycle, I bought it it hopes it would.

[TownsendsFJR1300]

Well, in any event, might try some (not alot) of some RTV or Yamabond on that seal. Put it on the seal and push it up into place but let it set up a bit.

That sealer should hold it B4 putting the LU back on.

Here's a pic of my LU off and I can now (never noticed it before) see where a seal touches the LU (where the exhaust obviously is) (circled in blue)..
I never had an issue with it coming off but I never messed with it either..

[99yam40]

I have never seen or heard of one falling out

maybe I need to look up inside my C40 next time I pull the lower unit to see what it looks like.

maybe it seals the exhaust stack to the muffler, not to the lower unit

[Soundear]

I ran water into the powerhead from a garden hose without the LU on, started it and listened critically with a stethoscope and detected no "knocks"! With the LU on my workbench, I drained my LU oil and discovered lots of metal dust on the magnetic tip of the drain bolt which suggests some improper gear meshing. First, i removed the shift shaft (like Rodbolt suggested in the past), took off the Castle Nut; removed and un-bent the tabs on the washer and even remembered to remove that tiny key prior to removing the driveshaft and bearing carrier. The LU driveshaft would not come out. I proceeded to remove the water pump and upper bearing casing which houses the upper seals and needle bearing. I also removed the thrust bearing. Both the driveshaft and prop shaft can be turned freely and move independently but can not be removed from the LU casing. It's my understanding that there's a pinion gear nut that has to be removed to free up both driveshafts. When I look into the prop shaft housing, I see the prop-shaft spindle with the bearing that normally rides at the rear of the carrier when assembled. That bearing appears to be pressed on to the prop shaft. The presence of that bearing prevents me from accessing the nut behind it to release the pinion gear to inspect all other gears in the LU boot for damage. Do I need a special bearing puller to remove the bearing on the ? The prop shaft area does not provide the room to set up a bearing separator or puller. The prop shaft spindle is in the way to use a blind inside bearing puller. Suggestions?

[99yam40]

I am fairly sure most pull the prop shaft and carrier in one piece, you can then remove the bearing after that

[TownsendsFJR1300]

I've never did it before before but per my shop manual, I believe the shifter has to come out first.

Yours may be different but I'd definitly refer to that before yanking hard on anything..


And GLAD it's NOT the engine knocking....

.

[Soundear]

I have a Seloc, Clymer and a Service manual. All state that certain models have the bearing pressed on to the rear of the carrier; others don’t as the bearing is pressed on the prop shaft. Each one states to put the shift rod in Neutral;
remove the bolts holding the shift rod and remove it carefully from the shift shaft without turning the driveshaft, pull on the prop shaft and it should come out like butter! The only thing I can think of is that some debris is clogging the shift slide release locking it into place! I really don’t want to waste a good bearing and race- I’m expecting a chewed up gear or something that no doubt will cost me a bit. I’m stuck!

[TownsendsFJR1300]

If everythings out as it should be, that bearing is probably damaged and way cheaper than any potential gears..

You now know the knocking was likely from the LU so I'd be expecting damage down there (besides metal bit's)

Sounds like you don't have much of a choice (or swing by a shop and double check before leaning on anything).

Good luck..

,

[99yam40]

I have a Seloc, Clymer and a Service manual. All state that certain models have the bearing pressed on to the rear of the carrier; others don’t as the bearing is pressed on the prop shaft. Each one states to put the shift rod in Neutral;
remove the bolts holding the shift rod and remove it carefully from the shift shaft without turning the driveshaft, pull on the prop shaft and it should come out like butter! The only thing I can think of is that some debris is clogging the shift slide release locking it into place! I really don’t want to waste a good bearing and race- I’m expecting a chewed up gear or something that no doubt will cost me a bit. I’m stuck!

how are you suppose to pull the pin(#52) that goes thru the clutch dog and prop shaft out ,
so the prop shaft can come out?
I would think the shaft, clutch dog, , gear, bearing, and carrier all needs to come out together
https://www.boats.net/catalog/yamaha...casing-drive-1

[Soundear]

Thanks for the suggestions and all your help. From what I gather, the clutch dog stays on the driveshaft on both clockwise and counterclockwise rotation motors until the prop shaft is removed. That clutch dog pin is taken out after a spring winding is removed from the outer concentric of the clutch dog itself. A near impossible feat to do without removing it from the boot! The difference between clockwise and counterclockwise rotation motors is the reverse pinion gear is on the opposite side of the forward pinion gear depending upon which motor you have. I have a standard rotation motor. It’s the shift shaft that pins the front of the prop shaft to the boot of the motor with the shift slide assembly and when in neutral, the pin holes align which allows the shift shaft tip to be pulled out of the motor freeing up the prop shaft. I suspect either a shim, bearing or a piece of the shift assembly fragmented inside the lower unit and jammed up one of the 4 ball bearings and jammed the slider that allows the slide shift to move freely and change gears working with the clutch dog. It’s probably why my reverse was hard intermittently at times to shift as fragments were getting caught and then freeing up. My next move will be to clean out the slide shift area as best I can Of any fragments and then put the shift shaft back in to be sure I’m in neutral in hopes it’ll pull out as designed. I could destroy the carrier bearing to get to the pinion nut and pull out the prop shaft as an option but first I’ll try to pull it out the way all manuals indicate you should. If anything, this motors been quite an education for me but as a weekend warrior with the weekend approaching it’s fitting. Any other suggestions are welcome as I will post my findings after I get home from work late tonight and plan my attack...