Alpha One Gen 1 - pressure test

OK I just got my drive back together and made a pressure tester thanks to iboats. My question is my gauge only goes to 10 psi is that ok? or should I get a new gauge that goes to 15-16?

I plan on vacuum testing the drive after is that a good thing or bad?

Re: Alpha One Gen 1 - pressure test

I have that exact same gauge as you and the way I look at it, if it holds 10psi and I see no bubbles when I spray around when soapy water then I consider it ready to go.

As far as a vacuum test, someone else may have to comment on that but the experts say to pressure test the drive, rarely do I remember them saying to also do a vacuum test or how to go about doing that properly.

Mark

Re: Alpha One Gen 1 - pressure test

You have both pressure and vacuum on that gauge. Seals generally only work well in one direction. That's why you have back-to-back seals on the prop shaft and drive shaft. The 'inside' seal stops oil getting out, the 'outside' seal stops water getting in. It's quite possible to have an outside seal leak and get water in the drive and still have the drive show a perfect pressure test. I prefer to do both pressure and vacuum for that reason, and as you have both pressure and vacuum on that gauge, it will only cost you a few minutes more of your time... Just be aware that the shift shaft only has an oil seal on it. When they get a bit older they can fail a vacuum test. (I usually replace it if it fails anyway).

One more thing. When anyone replaces back-to-back seals, they should ALWAYS fill the cavity between the seals with a marine grease. It helps prevent the seals from burning.

Chris.......

Re: Alpha One Gen 1 - pressure test

Thanks Mark and Chris!!!
My drive has held 10 psi for about 20 hrs with rotating the drive shaft every couple hours.

Chris the shift shaft oil seal you are talking about, is that the one between the lower and upper with a rubber washer and ss washer?

I am going to do a vacuum test since my gauge is ready to go. What pressure should I go to for a vacuum test? My gauge uses inches of mercury or centimeters of mercury.

Re: Alpha One Gen 1 - pressure test

Scroll down a little in this past post where the late, great Don mentions about that:

http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/vacuum-check-outdrive-522349.html

Mark

Re: Alpha One Gen 1 - pressure test

Thanks Mark!
I will go put vacuum gauge to 4 inHg and see what happens.

Re: Alpha One Gen 1 - pressure test

I went just went to take off compression test and realized I did not shift the unit (like other said to do while under pressure). It leaks when I put it in reverse(pretty bad leak, I can hear it). Is that the shift shaft rubber seal 12-31266 or something else??

Re: Alpha One Gen 1 - pressure test

HELP, Just took apart lower and found there is no shift shaft oil seal 26-816464 OR 18-8347 is that suppose to be on an Alpha One Gen 1 SN-OB655614?

This link show a oil seal Alpha One parts / lower gearcase drawing

Also found the shift shaft washer was destroyed (see photo).

Re: Alpha One Gen 1 - pressure test

What to replace other than the shift shaft washer 12-31266 if the shift shaft is leaking with a compression test??

Re: Alpha One Gen 1 - pressure test

Remove the bushing (special tool required, somewhere in the special tools section I think is a home-made one), fit a new seal and bushing 'O' ring, fit back into gear housing. Pressure and vac test... Slap on the new washers.... Хорошо сделанный
Chris.....

Re: Alpha One Gen 1 - pressure test

Thanks Chris it has been ordered.