Alpha Vacuum Test

[thegodown]

I'm in the process of replacing gimbal bearings, couplers, u-joints, yokes and a few other misc. parts in my twin V6 1985 270 Sea Ray. <br /><br />Last year I replaced the water pumps in my Alpha drives and they pressure tested with no problems. This year I found oil in the starboard bellows and am replacing the short yoke and seal.<br /><br />On the port Alpha, the pressure test is good, but I'm unable to hold a vacuum above 5 inches of HG. What is a minimum vacuum level I should accept before tearing down this drive and replacing it's seals?<br /><br />I was planing to go through the drives with all new seals and water pumps next year.<br />Thanks.<br />Dan.

 

[Don S]

Re: Alpha Vacuum Test

It's probably sucking air on the input shaft seal. The seal isn't designed to seal water out, and even new will only hold 5 to 10" of vacuum.<br />What you can do is to dip the drive backwards with the ujoints sticking up in the air. Then fill the seal area with gear lube and do your vacuum test. It will probably hold vac for a little bit before it sucks the oil into the drive.

 

[thegodown]

Re: Alpha Vacuum Test

Thanks Don. I'll try that.<br />With the oil surrounding the seal area, what sort of vacuum should I be able to hold before the oil is sucked in?

 

[thegodown]

Re: Alpha Vacuum Test

OK, so I followed your procedure and sure enough the vacuum held at 15 IN HG until the oil was sucked into the drive (took about 30 seconds). Do you think I can trust the seals for the season?<br />Thanks in advance.