How to find seal leaks in lower unit?

[StriperChaser]

I found about 1/2 cup of water in the lower unit of my 1996 Johnson 112 SPL the day before vacation. I changed the gear oil and ran it all week at the lake. When I checked it again there was only a trace of water when I cracked the lower plug. I drained the gear oil again and the oil looked good except the very last bit looked a little milky. I put 10 lbs air pressure on the gear case and sprayed the lower unit with soapy water while under pressure. I thought I had found a small leak at prop shaft seals. I tested it a 2nd time by applying air pressure to the lower unit while submerged in a water tank to the top of the lower unit. There was absolutely no sign of a leak but I lose air pressure in about 5 min. I replaced the shift shaft seals a few years ago and I change the gear oil yearly. What should I do next to find the leaks in the lower unit?

 

[srowland76]

Re: How to find seal leaks in lower unit?

Im having the same issue with my yamaha as far as water in lower unit, how did you go about pressure testing?

 

[Cofe]

Re: How to find seal leaks in lower unit?

Keep in mind that the drive shaft passes through the water pump and there are seals "orings" in there to keep the water out of the gear box. Also the gaskets on the water pump can leak. One of the most common leaks happens when a person doesn't replace the drain and vent gaskets every time they change lower unit lube.

 

[wilde1j]

Re: How to find seal leaks in lower unit?

Test leaking lower unit ? pressure or vacuum (both recommended)

1. Drain gear oil
2. Pressurize (or apply max vacuum possible) to no more than 15 psig with air (see OEM shop manual for max for your motor)
3. Submerge in water, look for bubbles
4. Possibilities
a. Drive shaft seal
b. Prop shaft seals
c. Shift rod seal
d. Cracked casting
e. Drain/fill screws/seals
5. Repair as needed

For V4 and V6 lower units, should hold some pressure or vacuum for at least 45 minutes.

If a seal(s) is found to be leaking, inspect the shaft (prop or drive) carefully for grooving. If there is any, make sure the new seal(s) do not seat in the same place as the groove.

 

[yorab]

Re: How to find seal leaks in lower unit?

Try to submerge the lower unit while under pressure. If you see no leaks, turn the propshaft as well. Sometimes the propshaft seal will leak more when the shaft is turning. I used a utility sink to test mine. The problem was that the water wasn't deep enough, so I had to flip the lower unit over in order to test the upper seals. It would be best if you had a deeper container so that you could submerge the entire lower unit at once.

 

[wilde1j]

Re: How to find seal leaks in lower unit?

A kiddie pool works fine and is usually available.

 

[StriperChaser]

Re: How to find seal leaks in lower unit?

To test for leaks I took a small bicycle foot pump and changed the air valve to a connector that fits the drain and fill holes. I cut a hole length ways in a plastic 55 gal drum and that gives me enough depth to submerge the complete lower unit. When I completed the pressure test under water and the air pump gauge showed no pressure there was still air in the gear box when I disconnected the pump. My confidence in that air gauge is not real high.

I drained and refilled the lower unit with gear oil for a second time replacing the fill and drain plugs with new. I had not replaced those plugs for several years. I'm going to run it a few more times at the lake and check it for water again at the fill plug. If any water is found I'll start by using a more reliable air pump. If the leaks are in the water pump area is there a way to test those without removing the lower unit?

 

[wilde1j]

Re: How to find seal leaks in lower unit?

How could you possibly tell where the leak(s) was without Xray vision??? You have a choice of drive shaft or shift shaft. By guessing, you have a 50% chance of being right!

 

[StriperChaser]

Re: How to find seal leaks in lower unit?

Well since I don't have X-ray vision there must be no way to tell where its leaking without removing the lower unit. Thanks for your help.