85hp Johnson Lower Unit Leak

[McGR]

I have spent virtually all my spare time over the past month ressurecting an old '76 Johnson '85hp. The motor is looking good and should be ready to run like a clock. Today (father's day) we were planning on taking the motor out for its maiden voyage. In preparation, I filled the lower unit with fresh lube last night. By the looks of things everything was on track and I'd soon be basking in triumphant glory. Instead, I was shocked this morning when I went to the garage to find a pool of gear lube below the motor. This surprised me, as I had replaced all the seals during my restoration project. Anyway, I eventually located the source of the leak. Fluid is coming from a factory machined hole on the left/port side of the gear housing. This hole is below the cavitation (anti-cavitation?) plate approximately opposite the vent plug on the starboard side. I tried pumping more fluid into the unit to see the results and found that,sure enough, as I pumped lube would exit the hole. After reviewing my parts and service manual, I'm completely perplexed as to why this is happening and what the function of this hole is. The hole is located below the seals and gaskets on the upper part of the lower unit and obviously above the prop shaft seal. So, what is its function?? I'm tempted to tap the hole and drive a set screw into it. Though, somehow, I've got a feeling this is not the generally recommended repair techniue for this problem. Anyone who knows what is going on, please let me know so I can possibly still experience "my moment of glory" soon.<br /><br />Thanks in advance...

 

[OBJ]

Re: 85hp Johnson Lower Unit Leak

Hi Mc...sorry that your "moment of glory" has been postponed.<br /><br />The hole your seeing is a cavity drain. The purpose is drain any water from the lower unit cavities that would other wise stay full of water. If your seeing oil coming out this whole, then a seal is leaking. I would suspect either the shift rod oring or the drive shaft seals under the pump. You may have to drop the lower unit to actually find the source of the leak.<br /><br />Let me ask a question, when your filling the lower unit, do fill from the bottom until the oil comes out the vent plug?<br /><br />Keep us posted....thanks.

 

[McGR]

Re: 85hp Johnson Lower Unit Leak

OBJ -<br />Thanks for the quick reply. I'm familiar with the drains in the upper part of the lower unit. This one almost seems too low. Nonetheless, I'm sure you're right, something in there that should be sealing isn't. I had a feeling the lower unit would be coming off again. Hopefully, I'll get to it this afternoon. I'll let you know what I find.<br /><br />Thanks again.<br />MG

 

[McGR]

Re: 85hp Johnson Lower Unit Leak

Problem Update...<br /><br />OK, I've pulled the lower unit, then the water pump and sure enough, the lube was coming from the drive shaft seals. This really frustrates me because I replaced the seals. Since I don't have a proper pressure tester, I'm using one of those relatively inexpensive lube pumps to judge the integrity of the seals on the unit. It seems this pump can relatively easily blow lube by the seals as I apply pressure. Could it be that this cheap pump is exceeding the pressure holding capability of the unit. Or, do I just need to start over and put new seals in and possibly clean the shaft better this time? By the way I used GLM aftermarket seals, anyone know of any issues with these?<br /><br />MG

 

[McGR]

Re: 85hp Johnson Lower Unit Leak

OBJ- <br />By the way I do fill from the bottom with the vent open. When I see fluid coming from the vent I quickly reinstall the screws. It was late last night, but I may have given a few extra pumps prior to installing the lower screw.

 

[OBJ]

Re: 85hp Johnson Lower Unit Leak

Mc....The lower unit will hold 15psi + when the seals are properly installed and the sealing surfaces are good. Heres an idea for ya', drain the lower unit, then drain the bottle the lube is in and us it for a test pump. May have to modify the cap so it will suck air or use a different bottle. Just get some air pressure in the lower unit. Dump the whole thing in a garbage can full of water and look for bubbles. Ya' got bubbles, ya' got a leak.<br /><br />Did you install the driveshaft seals back to back and is the sealing surface on the drive shaft smooth?

 

[McGR]

Re: 85hp Johnson Lower Unit Leak

Another update...<br /><br />After realizing my new seals were leaking,I realized that one way or another the seals would have to come out. So I went on a whirlwind trip to the only OMC(BMC) dealer in my area open on Sunday. He had the seals $12 each (ouch), but on Sunday when nowhere else is open, it's a bargain. I got to talking to the guy at the dealership about my problem... He says to me "did you remove the bearing carrier". I told him no and that I thought it was pressed in. He advised me it should come out allowing for easier installation of the seals. When I had originally installed the leaky seals I did not remove the carrier. In fact, I spent about 1/2 hour prying and beating on the thing until I came to the conclusion it was a press fit... wrong! Anyway, when I returned with my new seals today I immediately started working on getting the carrier out. Prying was again yielding no results, so I brought in the heavy artilliary, a hammer and chisel. One good whack on the corner of the carrier spun it loose. With the carrier now removed, I easily knocked out the existing seals. Upon closer inspection of the carrier I realized my error. I had also had a difficult time removing the original seals (with the carrier still installed) so I resorted to drilling out the seals so I could pry them out. Apparently, when i drilled my pulling holes, I hacked the daylights out of the bores the seals press into. So... I was not about to install the seals back into the damaged housing, it would only leak again. What to do... What to do... I know! JB Weld. Anyway I performed a minor miracle of JB Weld engineering by JB Welding the seals into the housing. I'm going to let it sit till tomorrow, at which point I should have a good idea if its holding pressure by simply pumping it up with my cheap lube pump. The day was not a complete loss as I did run the motor (for very short periods) without the lower unit installed and it seems to start immediately and idle fairly smooth. Also I did accomplish getting it mounted on my boat and got all the electrical and cables installed. So, when the lower unit is ready, I think we'll be ready to go. I'll report back as things progress.

 

[McGR]

Re: 85hp Johnson Lower Unit Leak

My final update... <br /><br />Today I reassembled the JB Welded bearing housing into the lower unit and filled it up with lube. After pumping it up considerably, I can say it is definitely not leaking like yesterday. In fact after filling it up and letting it sit several hours hasn't lost a drop yet. I'm quite confident that it's adequately sealed now. I also have no doubts about my repair to the bearing housing. It seems very robust. The only problem may be if the seals need replacement in the future, the housing will probably have to replaced also, as I think the seals are permanently JB Welded in place.<br /> <br />OBJ, thanks for your advise. Hopefully I'll be on the water in a couple of days in all my splendid glory.