Shift shaft leak

Hello everyone .I’m looking for some help with with a problem that I have.I’m trying to pressure test my lower unit on my older MC alpha I keep having a leak around the shift shaft seal and can’t figure out how to stop it. I have changed it with a new one. If anyone can help me out it would be greatly appreciated. Thanks for now

What year is your boat?

Do you know exactly what drive it is? Is it pre Alpha or Alpha? If the drive is original then the year of the boat will tell us what drive you have.

Maybe pictures would also be helpful.

Also a better description of how you are testing the drive? Are you testing fully assembled or the upper and lower apart?

What pressure are you using to test?

Any idea how many hours on drive?

did you use this or just the seal

View attachment 28434View attachment 28435View attachment 28436View attachment 28437Thanks for the reply. The boat is a 1977 Sea Ray Weekender. I think it is a pre alpha but the drive shaft does not have the pin on the top of it .The model # on the upper unit is 4640989 but I think the lower is not original because of the drive shaft and prop shaft. The engine in the boat is a 351 Windsor mercruiser 233 hp. I’m using a bike pump with a schrader valve on the end I can’t even get air to stay in the lower unit I have clamped over the oil passage to keep air from escaping there lm only testing the lower unit at this time. I realized that I forgot a washer between the clip a shift seal bushing so I put that in now the shift shaft stays down. Hopefully this bit of information helps.Thanks again.

I believe this is your parts break down

https://www.marineengine.com/parts/...0-thru-6225576/gear-housing-assembly-complete


The shift shaft seal

https://www.marineengine.com/newparts/part_details.php?pnum=MER23-30617A+2


This link is for reference only of parts and is a better picture to show all the shift shaft parts

https://www.marineengine.com/parts/...25577-thru-0d469858/gear-housing-driveshaft-r


Your attachments did not work.



Lets start with this question,

Where is the air leaking? At the shaft and seal or from the shift shaft bushing to gear case?

If it is at the shift shaft and seal, is there a groove on the shaft? Did you lightly sand the shaft with a fine paper to make sure it is smooth and burr free especially the splines that have to go thru the seal?

Use a good grease on shaft especially the splines and inner lip of seal so when you slide shaft thru seal you lessen the possibility of damaging the seal lips.


If leak is at bushing to case, Did you install Oring on body of bushing? Did you coat the threads and oring with Perfect seal?

check the shaft for and corrosion damage, I have some good, used ones available

I’m using the new shaft bushing and seal from the seal kit. I think the air is coming from between the seal and the brass bushing I put grease on the O ring on the underside of the bushing. Can I put prefect seal on the oil seal between it and the bushing or is grease enough

No perfect seal on seal lips. Grease only. Perfect seal is used for NON moving parts like o-rings and threads.

What pressure are you pumping up to? No higher than 15-17 psi. Typically 10-12 psi reveals leaks. In rare cases when there is a leak and its difficult to find you need the full 15-17 psi



So your leak is between seal and aluminum body of bushing? Not between seal lips and shift shaft? Please clarify.