Pressure/Vacuum Test Lower Unit Sterndrive Merc Alpha One Gen One.

[1985 Century Mustang]

I just did a pressure/vacuum test on my lower unit and the results were good, as I'm very pleased. I did a 15 lb. Test and the vacuum held up fine. No leaks no bubbles.

Question - How long do I do a vacuum test for? I did my test for 30 minutes. Do I need to go longer? If that is acceptable, my issue lies in the upper half, as I'm thinking it's the lower inner vertical oil seal, that's dumping gear oil out of the prop section. Your thoughts?

 

[1985 Century Mustang]

This is where the liquid was draining out when I used the soapy bubble test in the carrier bearing/ prop area, So I'm thinking that the gear oil definitely was coming down from the upper unit and coming out of the prop section.

 

[1985 Century Mustang]

Further, I had to hold/plug in this small oil passage seal to successfully perform the test. Luckily, I figured it out after the unit wasn't getting any pressure to accomplish this test. I didn't know that. You learn something new every day.

 

[1985 Century Mustang]

I will be replacing the lower vertical oil shaft inner seal. As the upper inner seal looks pretty good. I'm looking for a part # for that seal if anyone knows the correct part #. It's the smaller inner lower oil seal.

 

[kenny nunez]

The main purpose of the lower seal is to protect the upper seal. Once the lower leaks the lower end of the driven gear will rust which causes the leak. If you can, try to pressure the upper case, I am pretty sure it will not hold pressure. The bottom line is you will have to take the upper apart and closely inspect the seal surface. If it is pitted it can be repaired with a Speedy Sleeve along with the new seals.
Merc # 26-23511a2 seal kit. Sierra # 18-2648 seal kit
#27-9498a1. Gasket set. #. 18-261-1 gasket set

 

[1985 Century Mustang]

I will be replacing the lower vertical oil shaft inner seal. As the upper inner seal looks pretty good. I'm looking for a part # for that seal if anyone knows the correct part #. It's the smaller inner lower oil seal.

I found it at my local boat shop, I'm stoked. I'm installing it now. It fits perfectly. Gonna lightly sand the housing, and add some gasket sealer.

 

[1985 Century Mustang]

The main purpose of the lower seal is to protect the upper seal. Once the lower leaks the lower end of the driven gear will rust which causes the leak. If you can, try to pressure the upper case, I am pretty sure it will not hold pressure. The bottom line is you will have to take the upper apart and closely inspect the seal surface. If it is pitted it can be repaired with a Speedy Sleeve along with the new seals.
Merc # 26-23511a2 seal kit. Sierra # 18-2648 seal kit
#27-9498a1. Gasket set. #. 18-261-1 gasket set

Thanks for the info.