Johnson 40 HP LU Seal Problem

[gm280]

Okay I have my 1976 Johnson 40 HP engine nearing completion of being totally rebuilt. And once I get my computer working again and can post the pictures and progress I?ll do so. BUT, I have a problem now with getting the L/U prop shaft seal to actually seal. I?ve taken this unit apart now two times and still have a sealing issue. I installed a new seal and buttoned up the lower unit and then set up a pressure source to apply 6 PSI pressure per the Johnson shop manual but I am getting a leak around the prop shaft seal. It leaks at a constant rate of about 1 pound pressure per 15 - 30 seconds or so, any suggestions to fix it? I am ordering my third prop shaft seal now (I ruined the first one with some lacquer thinner?another story for another time) but I am going with an original OMC part this time. Any other ideas?? How is everybody solving such an issue and are others actually pressurizing their L/U?s to see if they leak before installing the L/U to the exhaust section?? :facepalm:

 

[boobie]

Re: Johnson 40 HP LU Seal Problem

Is the seal leaking around the OD or is it leaking around the prop shaft ??

 

[gm280]

Re: Johnson 40 HP LU Seal Problem

Is the seal leaking around the OD or is it leaking around the prop shaft ??

Unfortunately it is leaking around the prop-shaft. I wish it was around the OD where the "O" ring is, that would be a snap to fix, but it's not. I just ordered an original OMC prop-shaft seal and hope that solves the problem. I think I put an after-market part in there and YES there is a huge different as I am finding out now. The original prop-shaft seal is a lot thicker and the actual lip of that seal expends the entire width of the seal instead of only a thin little lip that is on this after-market part. I guess it was a learning experience...at least for me... :grumpy:

 

[boobie]

Re: Johnson 40 HP LU Seal Problem

Make sure the prop shaft area is nice and smooth where the seal rides. No gruves and ect.

 

[gm280]

Re: Johnson 40 HP LU Seal Problem

Okay folks here I am again. I received my NEW prop-shaft seal yesterday and I seem to have received the exact same type that I presently have installed. The one I removed originally was a much more robust version with a deeper lip seal then the ones I am presently ordering. I thought it was because they were after-market replacements, BUT I just ordered an OMC replacement number (but who knows) and I received the same thin single lip setup. SO I am once again going to tear into the foot and replace the seal once more in hopes this works and see if it will hold any pressure this time. It is getting old and I am wondering now how others accomplish their L/U's holding pressure. Mine leaks with just 6 PSI applied (per Johnson shop manual). Can’t wait to see what 18 PSI is going to do (next shop manual suggest)… The prop shaft is very smooth and there is absolutely no reason for any leaks that I can see, but it leaks all the same. Anybody had similar issues, and if so what did you do to fix it…other then replaced the new failing seal(s)? This seriously doesn’t give me any consolation in this foot being leak free for any length of time as well… :faint2:

 

[geoffwga1]

Re: Johnson 40 HP LU Seal Problem

I had problems getting a good seal on my 72 Evinrude 40hp.Are you quite sure it is the seal that is leaking and not round the outside of the seal housing.I don't mean the retainer housing where the o ring is but the seal housing itself.Did you apply Perfect seal before pressing the seal in? I found it best to leave it at least 24 hours to cure before any kind of test to allow the goo to harden,it took me three attempts to get it right.

 

[gm280]

Re: Johnson 40 HP LU Seal Problem

I had problems getting a good seal on my 72 Evinrude 40hp.Are you quite sure it is the seal that is leaking and not round the outside of the seal housing.I don't mean the retainer housing where the o ring is but the seal housing itself.Did you apply Perfect seal before pressing the seal in? I found it best to leave it at least 24 hours to cure before any kind of test to allow the goo to harden,it took me three attempts to get it right.

Ha, thanks for that suggestion. I never thought about that. I'll certainly make sure to use something with this next try. I have a can of Permatex 98H High Tack gooey sealer that I can use. Not sure where to get the "Perfect Seal" stuff. What I have could be the same stuff though. I know I didn't apply any while installing the prop-shaft seal for sure. I was more concerned with the "O" ring and the seal around that fixture and didn't apply anything to the prop-shaft seal at all. And, yes, that could easily be the entire problem now that you mentioned it. Thanks for jarring my thoughts on the subject. I think they even state that in the Johnson shop manual. I thought that as tight as the prop-shaft seal went into the housing that it couldn?t possible leak?boy was I wrong? Thanks again and I will update as I get the new seal installed? You live and learn...