Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

[capnstabbin]

Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

I have to replace this seal, shown in photo below, its cracked and in bad shape, not mention leaking, I think.


The photo below shows the oily milky fluid coming from exhaust after a few minutes (total 40 minutes running since de-winterizing, its not oil from that)


My question is since I have this apart should I also do the drive shaft seals?

And, how do I remove the bushing that is discontinued (cant order it) with out breaking it so I can get to the seal shown below

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Does the shift rod twist out, if so I think I can get a screw driver under the seal to pop it out and put in a new one.

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK, Got a private message from Frank A. the master ( Every Description he gives is perfect step by step instructions typed out like a photographic memory) and I can twist the shift rod out he says, gonna try it today, waiting for part to be delivered anyway. I was afraid of where ever I am unscrewing this shift rod from I would never be abale to catch the threads again to re-install it. I will attach photos.

 

[Frank Acampora]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Once you unscrew the shift rod it may be difficult to find the threads when you reinstall it. The pivot inside the gearcase has a square block that is threaded to match the shift rod and it is loose in the pivot arm. try not to move it. So, it is much easier to replace the shift shaft if the lower unit is disassembled but if you don't bang on the lower unit too much the block will not move. If it does happen to spin, you can fish for the hole with a piece of small diameter rod. I have had good luck by laying the lower unit on its side.

Unfortunately for you, you have a newer lower unit. On older lowers, if you removed the water pump base, the seal came with it and you didn't need to remove the shift rod. AND, with the pump base removed, you could see right dowm the where the rod screws in.

To replace the drive shaft seals, you need to remove the water pump. Whether or not you should do it now depends upon how much fuss it is for you to drop the lower unit. If it doesn't take much effort and the seal appears to not be leaking, don't bother replacing it. If, on the other hand, you would prefer to not drop the lower unit again at a later time, OR if you suspect a bad seal, then yes, go ahead and replace it now. Changing the prop shaft seal does not require dropping the lower unit, so if it appears to be OK, don't do it yet.

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK, here is the next question.

As it was my first time removing the lower unit I was not looking for this part, but today I found this seal up inside the drive shaft housing 3 days after I removed the lower unit. I just decided to look up inside the housing of the drive shaft for some reason, and staring me right in the eye I found this seal, according to the service illustrations this seal has the fatter end pointing up, but I found it pointing down.



Like I said this was my 1st time removing this lower unit, so I am not sure which direction it was supposed to be in, but also I did not find it for 3 days later. It was wedged in a narrow (bottle neck) inside section of the drive shaft housing.

If anyone knows what direction it should be installed, and if its not major thing, please let me know.

 

[Squab]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Hey Captn' it looks to me like a water seal which would mount on the water pump. On the water tube not the drive shaft.

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Maybe, but thats not where it was found....after a further investigation, I believe its where the drive shaft is inserted up the housing

 

[pnwboat]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

I suspect it might be a spline cover on the top of the drive shaft. Covers the splines on top of the drive shaft where it is inserted into the crankshaft. The older Force motors have a similar setup. It's not uncommon for them to fall off the end of the drive shaft as you pull the lower unit out of the housing. That's my guess anyways.

 

[Frank Acampora]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Look around for a steel collar that fits over the splines on the drive shaft that the rubber sits into. Correct orientation if you have a steel collar --not too sure about the '98-- is steel collar on the shaft with groove up, flat end of rubber down into the groove, and beveled end up to match the bevel in the crankshaft.

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Frank would the steel collar be stuck up by the power head? Because I do not have one and I dont see one, and from looking no other parts fell out.

 

[Frank Acampora]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

As I said, I'm not sure on the '98 whether or not it has a steel collar. If it has one, It probably would have come off with the rubber. If it has on, there will be a small land to locate it, on the drive shaft, just below the splines. If it were tight, it would still be on the top of the drive shaft.

Your schematic only shows the shift rod. See if the collar is shown or listed on the full parts diagram for the lower unit. If it is shown, then look for it. If not shown, it is not used.

 

[Squab]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

Show a picture pal. what does it look like?

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK, so the picture is above of the seal, I never found a retainer ring with it. I have attached photos below of the bottom view of the drive shaft housing. Marked is where I found it.


So how important are both of those parts, the ring and the seal?


Next I have been hunting down parts for this project and finally I think I have them all.

The impeller looks good, so I did not buy a new one.

The prop shaft seals are part of this project as well, so when removing the deeper one, I do not remember how to it was positioned (which side out).

What direction/side of the bottom (deeper) seal go?


The one on the left looks incorrect and does not seem to fit. the one on the right seems good with the bottom seal flipped, the top seal stays the same

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK here is a photo of all the parts I am replacing plus water pump gaskets, not in the photo.
Plus a photo of the prop shaft carriage removed,,,,new parts are closest

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK here is a photo of all the parts I am replacing plus water pump gaskets, not in the photo.
Plus a photo of the prop shaft carriage removed
View attachment 88825View attachment 88826

 

[capnstabbin]

Re: Shift Shaft Seal Replacement - 1998 75 HP Mercury Force

OK, so I =had to figure the the seals went in the way I thought was good, it was actually the only way, I had no way pounding the 1st prop shaft seal into place in the other direction, basically the spring loaded side faced inside the gear housing. That was the only way it would fit.

Pictured below is my brand new shift shaft seal, I think this was the culprit the whole time but I am a little suspicious of the o-ring on the prop shaft carriage, thats why I replaced it. The prop shaft seals cost the most but most likely were not the issue, I saw no signs of leakage on them.

Next which will be started in a new thread will be what ever is going on with my drive shaft seals and retainer ring