pressure test for lower unit

[oaklander]

I have a 1955 Johnson 25hp outboard model RD-17. I would like to pressure test the lower unit to check for leaks. Can anyone tell me at what pressure to test this and is there any thing else I can do to check for leaks.

 

[rolmops]

Re: pressure test for lower unit

The advice is usually to test it at a max of 10 pounds and see if it holds that for 10 to 15 minutes.
If you have steady over pressure it may be that you have a vacuum leak,so you will also have to check for that one.
These old engines often have a worn propeller shaft at the point where the shaft exits the housing.What is often done to fix that problem is doubling up on the seals.On to keep the oil in and one to keep the water out.

 

[wbeaton]

Re: pressure test for lower unit

To be honest. I have yet to see a 1950's OMC that still has good original seals. You might as well replace them now. Besides, you'll get the piece of mind that comes with good seals and you also get to see what condition the gears and clutch dog are in.

The seal kit is about $30 and it'll take you a couple hours or so to change them if you've never done it before.