Lower Unit still leaking after replacing seals

Hi,
I'm fairly new to this Forum, as well as Outboard Repair. I bought a 1962 Starcraft a couple weeks ago, that has a 1966 18Hp Evinrude Fastwin on it. Boat had sat for 8 years prior to me getting it, and I did know enough that seals would have to be changed. Anyway, guy I bought it from had started it for me and it sounded pretty good, but once I got it home I checked Lower Unit Oil. Was None, so I filled it. Ran it for awhile in barrel and made sure water was circulating, and it was, but motor was sounding a little rough and it wouldn't shift into Forward, come to find out the forward gear and clutch were worn pretty bad, but I was able to get it redone at a machine shop, and it works well now. Also when I checked Lower Unit lube after running it, it was milky white. So I purchased a Sierra Seal kit that had absolutely no instructions with it, but the shop where I bought it said it's real easy to do(maybe if the drive-shaft O-ring weren't just about disintegrated and in the bottom of lower unit). So, I searched and searched and thought I figured out where everything went, but the O-ring that goes on the drive shaft I really wasn't sure about, and what I am assuming was the Drive-shaft O-ring that came with kit looked way to small, about a 1/4 inch in diameter,and not even a 16th of an inch thick, so I had some other Other O-rings kicking around and found one that looked about the size of the tiny piece that was left over from the disintegrated old one, and I placed it in the groove just below the spline of the top part of the drive-shaft. Also, the Spaghetti seal looked a little on the thin side, but what do I know? And the Drive-shaft seal and the Drive seal were only about half the thickness of the ones that were in there, don't know if that matters or not. Also did the water pump repair kit, minus the housing, as it didn't look that bad to me, and I just couldn't afford the $68.00 for a new one. So, after staying up all night doing this I put the finished motor back in the barrel, water seems to be circulating fine, but then I see oil quickly gathering in the barrel of water, so I shut the motor down, only to see the dreaded milky white oil-water mixture oozing from a hole on the back of the lower unit. I don't know what to do now, especially with no service manual, and I am out of money now. Is it salvageable without having to dump more money on another seal kit? Really would like to get this in the water soon, before the Summer is over. I could really use some help from some of you MUCH MORE EXPERIENCED BOATERS out there, and any help offered would be greatly appreciated.
Thanks So much in advance!

Pressure test it under water and see where its leaking. If your losing oil to the point its noticeable in the barrel then you have a major leak.

Whoopbass said:

Pressure test it under water and see where its leaking. If your losing oil to the point its noticeable in the barrel then you have a major leak.

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Thanks for replying, but how do I do the pressure test? I'm new to this

The bottom screw where you put in oil is where I made a piece that screws into the fill hole that I can hook air up to (5lbs)I check a rebuild before I put oil in.

There is a seal under water pump,was it replaced?

crazymanme2 said:

The bottom screw where you put in oil is where I made a piece that screws into the fill hole that I can hook air up to (5lbs)I check a rebuild before I put oil in.

There is a seal under water pump,was it replaced?

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yes it was

The O-Ring that looked too small is actually the shift shaft O-ring (which you apparently did not replace). Aside from the propshaft seal that is the most common cause of a leak in the old gearcases. The brass bushing has to be driven out and the o-ring can be replaced. Takes a special tool (driver) to do it properly. Go to https://www.aomci.org. then to the ask-a-member section and look up Frank Robb and have him send you a tool. They are inexpensive.

Pappy said:

The O-Ring that looked too small is actually the shift shaft O-ring (which you apparently did not replace). Aside from the propshaft seal that is the most common cause of a leak in the old gearcases. The brass bushing has to be driven out and the o-ring can be replaced. Takes a special tool (driver) to do it properly. Go to https://www.aomci.org. then to the ask-a-member section and look up Frank Robb and have him send you a tool. They are inexpensive.

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I second what Pappy said!! I have one of many of Franks tools and they work great and are very reasonably priced. I have used the specialized tool to remove the shift shaft seal and you have to split the lower halves of the gear case to get to the seal. You have to drive it out from inside.



Hear are a couple of videos that may help you out if you are a visual learner. They are not the exact motor but are very similar.

https://www.youtube.com/watch?v=tA0u62hciwY&feature=related

https://www.youtube.com/watch?v=a_-ZfbUNT3A&feature=related

Good Luck....you have a very good motor. Well worth fixing!!!

Pappy said:

The O-Ring that looked too small is actually the shift shaft O-ring (which you apparently did not replace). Aside from the propshaft seal that is the most common cause of a leak in the old gearcases. The brass bushing has to be driven out and the o-ring can be replaced. Takes a special tool (driver) to do it properly. Go to https://www.aomci.org. then to the ask-a-member section and look up Frank Robb and have him send you a tool. They are inexpensive.

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Thanks for responding Pappy, I appreciate it. I did replace the shift shaft o-ring, that is not the o-ring I was talking about. The o-ring I was talking about is a little bit smaller in diameter, and about a 1/5th of the thickness. The reason I am thinking that an o-ring goes on the top of the drive shaft, is because there was remnants of one in the grove just below the spline that goes into the power head. Only problem is, that the o-ring that was in the kit is much smaller than the one that came out. Also, the following link https://www.marineengine.com/parts/vintage-evinrude-johnson/278779/catalog.html?https://www.marineengine.com/parts/vintage-evinrude-johnson/278779/27877900001.htm has a parts diagram for the lower unit (1966 18hp Evinrude Fastwin) page 12 reference # 11 that shows a o-ring that goes on drive shaft, but does not show where it goes. Everything else has been replaced, (shift shaft o-ring, drive shaft seal, Gear case Head o-ring, and propeller shaft seal)

Thanks for the video links cajuncook1

That reference number refers to the driveshaft o-ring that is installed at the top of the vertical driveshaft to seal the grease in the splines. At this point you are going to have to remove the gearcase and lightly pressurize it (5# or less) and find the leak with soapy water.

Pappy said:

That reference number refers to the driveshaft o-ring that is installed at the top of the vertical driveshaft to seal the grease in the splines. At this point you are going to have to remove the gearcase and lightly pressurize it (5# or less) and find the leak with soapy water.

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Thanks again Pappy :beer: Now if I could just find out for sure the actual size of the o-ring that is supposed to be there, cause I really don't believe it was the little tiny thing that was enclosed in the bag. But, the one I put on there looks about right