1975 Mercruiser 233 Outdrive Issues

[Brandon5778]

Hello all, I am in need of some guidance. I'm trying to get my dad's boat back on the water for him, the goal is by the 4th of July, but we'll see.. Due to some financial circumstances he can no longer afford the price of a mechanic. The boat is a 1975 Mercruiser 233 (351ci Ford motor). He's had the lower unit replaced about 4 years ago, and bellows and shift cable replaced about 2 years ago.

The problem he's been having namely is milky gear oil. The boat also started taking on water, although we had the bellows replaced by a mechanic with only 1 season of use on them. Upon removal of the drive we found water inside the U-joint bellows and again milky gear oil. I am trying to tackle sealing the drive and then figuring out why there was water in the U-joint bellows. Along with sealing the drive, we also want to replace the U-joints as they are rusty and service the water pump impeller. After a lot of reading I built a pressure tester for the drive. It will not hold ANY pressure at all. The air is coming out of the seal that the yoke assembly passes through.

So I think what I need is an upper unit seal kit. Sierra p/n 18-2644 seems to be it (could someone please check me on that?). From what I've been reading, I should replace the seal that I know is leaking, reassemble the drive and pressure test it again. Or should I just overhaul all the seals? Keep in mind I have never done this before, but I am very mechanically inclined and I know I can figure it out if you all are willing to help. What are the things I will need to know to do this job? As far as tools I have a spanner wrench coming and I should have anything else I'll need. And finally, what are your thoughts on the water in the U-joint bellows? I don't know how it all works, but I thought the bellows alone sealed that area off from water, they are new and show no signs of damage. Is it possible for water to get in through the bad seals on the outdrive? Again the drive would not hold any pressure at all. Thank you for reading, I appreciate any and all comments.

 

[Bt Doctur]

water in the bellow is from a leaking below, damaged bellow, improper installation of a bellow, extremely high bilge water level

could be just the upper sal but in most cases the yoke is also grooved, dis-assemble to inspect

 

[Brandon5778]

water in the bellow is from a leaking below, damaged bellow, improper installation of a bellow, extremely high bilge water level

could be just the upper sal but in most cases the yoke is also grooved, dis-assemble to inspect

Ok, so I definitely have two separate problems here. I will try to figure out what went wrong with the bellows installation, as we never had high water level in the bilge. Would this upper yoke seal let water into the gearcase and cause milky gear oil if there was water in the bellows? I will see if the yoke is grooved, waiting on the spanner wrench to get here on Tuesday.

 

[Scott Danforth]

any water in bellows rusts the u-joints and the shaft, then takes out the seal.

 

[Fishermark]

On a boat that old you need to check the bell housing for corrosion. A common problem with older boats. If the lip is corroded it is difficult, if not impossible to seal the bellows. This is certainly true if it is a salt water boat.

And yes, on the upper seal.... I would suggest buying the upper yoke and putting a new one on. If memory serves, you can speedi-sleeve it, but a new yoke isn't that expensive.

 

[Brandon5778]

any water in bellows rusts the u-joints and the shaft, then takes out the seal.

Yup, that makes sense. So have you heard of that then going on to causing milky gear oil?

On a boat that old you need to check the bell housing for corrosion. A common problem with older boats. If the lip is corroded it is difficult, if not impossible to seal the bellows. This is certainly true if it is a salt water boat.

And yes, on the upper seal.... I would suggest buying the upper yoke and putting a new one on. If memory serves, you can speedi-sleeve it, but a new yoke isn't that expensive.

The drive is in good shape, fresh water use only. Boat has never been left in the water and always stored indoors its entire life, so corrosion shouldn't be too much of an issue. I'm starting to lean toward installer error. I'll plan on buying the new upper yoke.


As far as parts for this ol' girl, can anyone help with that? I've found everything I need except I'm not sure about the upper seal. I believe it is included in the Sierra 18-2644 Upper Seal kit, but I can't really find anywhere to confirm fitment.

 

[kenny nunez]

My past experiences with water in the bellows after it has been replaced or the drive was R&R to check alignment and grease the joints is the large rubber ring not being glued in place and pulled out of place fighting to install the drive without it being properly supported.
As the previous posts advised you need to replace the yoke, joints, gimbal bearing and related seals. Try to rig up a way to hold the drive where all you have to do is push it rather than try to balance it while installing and be sure to use a good adhesive to hold that ring in place.

 

[Brandon5778]

Update. Got the gimbal housing tore apart. Found my leak. U-joint bellows had a small tear in it. Also, it looks like whoever did the shift cable bellows did not use the little clamp on the small end? Pictures attatched. So, water got in from the failed U-joint bellows, took out the gimbal bearing, took out the upper drive yoke seal, and then started letting water mix into the outdrive gear oil. Sound about right? Note the failed bellows was a Sierra aftermarket brand... Mercury wanted double the price and we went the cheap route.

 

[Brandon5778]

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