140 alpha trouble replacing gearcase

[mike64]

After replacing the impeller, I'm trying to get the gearcase back on but every time I get it to within a half inch and it will not go any further. I think I have the shift shaft in the housing because I can move that little tab on the housing and feel it moving the shift shaft.

Any tips? I don't want to force it.

 

[dingdongs]

Re: 140 alpha trouble replacing gearcase

sometimes the main shaft may need twisting a little and as you have it in drive just rotate the prop so long as you know all other stuff is located.a bungee wrapped around takes the strain sometimes so you can reposition your self every now and again as its luck of the draw if it goes in straight away.

 

[stonyloam]

Re: 140 alpha trouble replacing gearcase

Drop it down a little, and turn the intermediate shift shaft all the way clockwise. Turn the prop counterclockwise, and it should lock. Put a bungee on it to hold it in place (the gearcase is now in forward). Check the shift shaft to make sure it is pointed straight ahead, and make sure the control lever is WOT forward. If the ss is not pointed straight ahead lift it up and reposition it on the splined lower ss. You should be good to go to put it back together. You may have to turn the prop a little to line up the splines on the driveshaft, turn it counterclockwise only. Good luck.

 

[mike64]

Re: 140 alpha trouble replacing gearcase

I put my finger up where the driveshaft receiving splines are to see if there was any obstruction, and I found this mangled seal up in there. Must be a mate to the o-ring on the driveshaft. Looks like my simple impeller replacement is over until I can get to the boat store and pick up another one of those little seals, and that ain't happening today #$@$%%^#@

 

[Fishermark]

Re: 140 alpha trouble replacing gearcase

It sounds like what you are calling the gearcase is the lower unit - correct?

You can throw away the o ring on the top of the drive shaft. It is not only unnecessary, it can actually cause problems. Mercruiser recommends doing away with it. In fact, newer models do not even have the provision for the o ring groove on the shaft.

How's the seal itself in the upper unit? If there is a doubt as to its condition, it is wise to replace it. It is cheap and easy to replace.

 

[dubs283]

Re: 140 alpha trouble replacing gearcase

to be technical, the lower half of the entire drive unit is called the gearcase, the upper half is called the driveshaft housing

i have never heard anyone at mercruiser or otherwise mention not installing the o-ring on the driveshaft, it is there for a reason - to help seal the driveshaft

the part in the picture is the inner protion of the lower seal in the driveshaft housing - actually quite easy to replace

use a two jaw puller to yank out the remnants fo the old seal, clean the mating surface of the case where the seal fits, use blue loctite on the od of the new seal and install

be sure to grease the lips of the new seal and put spline grease on the driveshaft before you go back together

 

[mike64]

Re: 140 alpha trouble replacing gearcase

Thanks dubs, good info.

Man...I got pretty comfortable working with my OB and then I have to go and get an I/O and it's a whole new ballgame. Now that I was up in there trying to get the gearcase on I notice the watertube has some cracks in it and should definitely be replaced, although the bellows look good. I might punt and just take it to a shop to get it done. Found one nearby online that sounds reputable. Given enough time I'm sure I could make these repairs, but I got a million freakin things to do around the house and I'd like to get the boat out by the 4th of July...

 

[Fishermark]

Re: 140 alpha trouble replacing gearcase

to be technical, the lower half of the entire drive unit is called the gearcase, the upper half is called the driveshaft housing

Fair enough. Not busting anyone's chops - just making sure we are talking about the same thing.

i have never heard anyone at mercruiser or otherwise mention not installing the o-ring on the driveshaft, it is there for a reason - to help seal the driveshaft

I don't have the bulletin handy... maybe someone can chime in. But if you will note the newer ones do not even have the groove for the o ring. It is my understanding that it caused more problems than it solved, and was decided it was not needed. If you do a search, you will see quite a bit of info on it. Here's a recent post: Post asking about driveshaft seal and oring

 

[dubs283]

Re: 140 alpha trouble replacing gearcase

the groove on the drive shaft is indeed for an o-ring

the reason the newer ones do not have the groove is because the gears are cut the opposite way - thus forcing the driveshaft upward (into the driveshaft splines as it were) when in motion

if the o-ring is unneccessary, why then does merc still include it in the water pump kits??

 

[stonyloam]

Re: 140 alpha trouble replacing gearcase

if the o-ring is unneccessary, why then does merc still include it in the water pump kits??

Probably because they only want to stock one kit for all, and the manual says to use the O-ring if you have the groove.

 

[Fishermark]

Re: 140 alpha trouble replacing gearcase

the reason the newer ones do not have the groove is because the gears are cut the opposite way - thus forcing the driveshaft upward (into the driveshaft splines as it were) when in motion

That relates to the pre-load pin that some of the older models have - and has nothing to do with the o-ring.

Hey - if someone wants to use the o ring... more power to them!

 

[mkast]

Re: 140 alpha trouble replacing gearcase

to be technical, the lower half of the entire drive unit is called the gearcase

Mercruiser calls it a gear housing.

 

[mike64]

Re: 140 alpha trouble replacing gearcase

the part in the picture is the inner protion of the lower seal in the driveshaft housing - actually quite easy to replace

use a two jaw puller to yank out the remnants fo the old seal, clean the mating surface of the case where the seal fits, use blue loctite on the od of the new seal and install

be sure to grease the lips of the new seal and put spline grease on the driveshaft before you go back together

Thanks dubs, I picked up a new lower driveshaft housing seal and I see it's got a metal outer part- just like the grease seal on a trailer hub. Felt up in there again and I can feel the metal part of the seal fitted in there. Doesn't seem like it'll be too hard to replace. I'll have to pick up a 2 jaw puller.

I decided to give up trying to take it to a shop- everyone around here is backed up 2 weeks. The look of the water tube concerns me, but I'm not going to attempt to remove the driveshaft housing right now. I read in another post that the water tubes are pretty durable, so I'm hoping the cracking is not as bad as it looks and it'll hold out for the season, and I can tackle the job in the fall or take it to a shop when things have slowed down.

 

[mike64]

Re: 140 alpha trouble replacing gearcase

use a two jaw puller to yank out the remnants fo the old seal, clean the mating surface of the case where the seal fits, use blue loctite on the od of the new seal and install

be sure to grease the lips of the new seal and put spline grease on the driveshaft before you go back together

I couldn't find a two-jaw puller in the right size and configuration to get in the small space, but I did find this seal puller. Any reason why I couldn't use this to remove the lower driveshaft housing seal?

 

[dubs283]

Re: 140 alpha trouble replacing gearcase

if it is long enough so the handle part clears the driveshaft housing mating surface, yes

might have to try popping one edge of the seal, then the other until it comes out

 

[mike64]

Re: 140 alpha trouble replacing gearcase

Yeah, it's definitely long enough to get to the seal. Tapping it out on each side is a good call, Thanks dubs.

 

[mike64]

Re: 140 alpha trouble replacing gearcase

Ok, got the seal replaced and the gearcase back on with the help of a friend, but when I turn the prop clockwise it clicks once per revolution. It might just be the impeller I'm hearing, but I'm suspecting the gearcase may have gotten shifted out of first gear with all my jacking around trying to get it on. The service manual says, "if the propeller shaft is rotated in a clockwise direction before shift shafts are coupled, gear housing must be shifted back in forward gear and held in position". But how do you know whether the gear housing is in forward or not?

 

[dubs283]

Re: 140 alpha trouble replacing gearcase

how do you know whether the gear housing is in forward or not?

with the drive halves apart, looking down at the splined shift shaft (in the gearcase) - rotate the shaft clockwise while turning the driveshaft clockwise as well

the shift shaft will rotate until the clutch locks into the gear and the propeller shaft rotates in FWD gear

when reassembling the drive halves make sure the gearcase stays in FWD gear while coupling the shift shaft into the shift fork in the driveshaft housing

 

[mike64]

Re: 140 alpha trouble replacing gearcase

Before I saw your reply dubs, I read a thread that said to turn the gearcase shifter spline all the way clockwise, but it didn't say to turn the driveshaft clockwise too. So I turned the shifter as far clockwise as it would go, and it was at a definite stopping point. But I didn't turn the driveshaft at all. I got the gearcase back on, put gearcase oil back in, put ti in neutral, started up the engine and had a friend put the gear slightly in forward for a couple seconds to see if it went into forward gear. The prop turned but there was a clicking sound that didn't sound right. It almost sounds like it's between gears or something, like maybe the shifter was turned one spline off .....?...?

 

[dubs283]

Re: 140 alpha trouble replacing gearcase

like maybe the shifter was turned one spline off .....?...?

could be, but if that were the case it would shift into the other gear (REV) before getting to the detent on the shifter i.e. - would go into REV very "quickly"