checking lower unit--pressure or vacuum?

[loopcharge]

I've got a 1972 Johnson 65 hp and when I went to make my yearly lube change on the lower unit, it was milky. At least there weren't any metal chips and it couldn't have more than a couple hours this way, so hopefully it will be ok. As for checking for the leak, I've read most of the postings here and they all say to pressurize the unit with about 10 psi, same as the shop manual. A few people suggest a vacuum check also. Is it really necessary to do the vacuum check also?

 

[Dhadley]

Re: checking lower unit--pressure or vacuum?

Do both. The term "pressure check" is another one of those terms that is a little misleading. To those in the industry it includes a vacuum check also. At least it does to the quality orientated techs. <br /><br />Good question!

 

[loopcharge]

Re: checking lower unit--pressure or vacuum?

Thanks Dhadley appreciate the reply. Would you say 10lbs. is a good number for both vac and pressure?

 

[ob]

Re: checking lower unit--pressure or vacuum?

Vacuum is measured in inches.All either will determine is the size of your existing leak.If you've got milky oil you've got a leak somewhere.Propshaft seal,shift rod housing seal driveshaft seal,or fill and vent plug seal washers.