Johnson 18 Crank Seal Replacement- Should We Be Doing This??

[Daveparm]

Hi all, I just started getting into old outboards over the last few weeks. My first purchase was a Evinrude 1958 5.5 and now I'm hooked! I now have two 5.5s and two Johnson 18's a 1957 and a 1965. It's hard to believe the parts support for motors this old!!! I just started working on the 1957 and now that I have the flywheel off I started thinking about seal condition of these old motors. The upper crankshaft seal seems O.K. (no oil leakage) but will probably change it for safe measure as it's awesome that I won't have to split the case (no lip on seal) to do it. Is the lower seal (bottom of powerhead) the same, and anyone have experience replacing theirs? My reason for wanting to change these is fear of a leak causing a lean condition at WOT that would cause motor damage. Should this be a concern, or should I just not think about it and go have fun! In other words, how many of you with these old (beautiful) motors are running original seals? Thanks.

 

[F_R]

No Title

The lower seal is a fairly complex carbon seal assembly. OK, it is possible for it to break or come off the shaft, and admit water into the crankcase. But they are pretty reliable and I wouldn't go in just for that, without evidence of leakage. Don't worry about either causing a WOT lean condition.

 

[Daveparm]

Thanks, that's good to know. I did analyze photos of the crank and was wondering how that seal worked as it appeared to be small diameter- carbon seal makes sense.. How is the carbon seal cooled? Is it by water or from the oil mixture? With the ability to adjust high speed mixtures on the fly with these older motors would you be able notice and even tune out (or at least compensate) for a lean condition? BTW, what is the procedure for fine tuning the high speed knob. I understand the low, but not quite sure how to adjust high. Can you explain? I am a worry wort, because I have rebuilt a few yamaha pwc motors that failed due to bad crank seal lean out. Thanks for the quick response!

 

[F_R]

The carbon seal is lubricated by the oil that you put in the gas. Your 1965 should have a fixed high speed jet, no adjustment needed or possible. The '57 has an adjustable high speed needle, which is capable of dumping in way more gas than it could possibly burn. You adjust it on a boat, on the lake. Run at full throttle and slowly turn the knob to the right till it starts to falter, then back to the left till it regains power. Of course both motors have adjustable low speed needles. They are adjusted the same as the h/s except at slow idle. If it is any comfort, I was an outboard dealer's mechanic for over 20 years and I don't think I've ever seen an 18 damaged by lean fuel/air mixtures. Some highly tuned big motors yes, but not 18,s

Stop worrying. Those 18hp motors are about as basic as you can get.

 

[Daveparm]

Awesome, my worries are set to ease! Thanks for the through writeup. I haven't had the 65 on the water, but come to think of it- your right - no high screw. I bought the 57 from someone who replaced the carburetor. Based on my impression of him, it wouldn't have surprised me if he used a carb from another motor (9.5 or 15 if they are the same style carb) Is there a way to confirm jet size (do they unscrew and are they numbered with relation to flow like standard carbs) or should I look for a number stamped on the carb if they are cast in?

 

[F_R]

It unscrews. You are supposed to use a special screwdriver with parallel flats. An ordinary tapered screwdriver may spread the soft brass, making it harder and harder to remove. Once it is out, it should be stamped 64. That means 0.064". It is a precision hole. No way in heck does it have a 9.5 carb.

 

[Daveparm]

Thanks again for your wisdom. Researching the correct jet number would surely have taken many hours if I could even find it. Thanks

 

[HighTrim]

Me personally, I always change the upper crank seal on a 50s/60s OMC if I have the mag plate off anyways. Especially, if they have been sitting for decades. The rubber dry rots. I buy them in bulk, and always have them on hand.

Regarding the lower crank seal, the carbon seal, there is an o ring inside the carbon seal which usually needs changing. As Frank said, I would not pull the powerhead to do this, especially if the motor is running well.

For sure I do them on the small hp motors that require pulling the powerhead anyways to drop the gearcase and change the impeller like the 5.5s and 7.5s. Always have a new o ring handy if you know you are tackling this. The lower carbon seal assembly is critical in preventing water ingress into the powerhead on them. When you find one detonated, this is usually why.

 

[Daveparm]

I plan to do impeller/possible gear case work on the 5.5's, so i already removed the powerhead. To pull the carbon seal to get to the o-ring, do I need to split the case.
Just so I know if I ever have one of the 18's powerhead off, is it the same procedure?

I do have the mag plate currently off the 18, so I will change the upper seal as per your suggestion. Is the sheet metal screw trick the best way to remove the seal being that I don't have the special tool?

Final slightly unrelated question. I took the mag of the 18 to replace the plug wires. Should I go with oem, or sierra, or other? Boot recomedations? In other motors I always used NGK, but are the oem ones with the little coil inside better?

 

[racerone]

The carbon seal is installed on the crankshaft AFTER the powerhead is closed up.----When powerhead is off it is easy to inspect / maintain.

 

[F_R]

If you think you might have use for it, Richard White makes a seal puller for that top seal that makes it a piece of cake. www.richardsoutboardtools.com

 

[Crosbyman]

if you don't have it you need this book

http://boatinfo.no/lib/johnson/manuals/1922-1964johnson.html#/0

http://boatinfo.no/lib/johnson/manuals/1954johnson55owner.html#/0

 

[Daveparm]

Crosbyman, thanks for the manuals--they are awesome!

While looking at the lower 5.5 seal I really don't understand how to service it. How is it removed/o-ring serviced? I couldn't find it in the manual. Page 252 references a c clip-(retaining washer), which doesn't seem to exist on the 5.5

I will be sure to reach out to Richard with inquiry of his upper seal puller.

Thanks

 

[F_R]

No Title

The parts simply stack on the upper end of the drive shaft. The gasket contacts the bottom of the powerhead to complete the seal. The gasket and o-ring should always be replaced any time you have it apart. Other parts as necessary.

 

[Daveparm]

Lol, I get it now. I took the powerhead off a little over a week ago, and forgot obout what I took off. Just looking at the bottom of the block made no sense.

 

[Daveparm]

The links to the manual above are awesome. It would be nice to have a download able version that I could print. I know I can print buffered pages, but printing the whole thing at once would be awesome. Anyone know of a source? I am definately not complaining, as this online one is great as well. Sorry if this is to far off topic.

 

[Daveparm]

As the Original Poster, I just wanted to follow up this thread with my experience with Richard White who make some specialized tools for our motors. I ordered a upper seal puller for this motor and when it arrived, noticed that it was to snug around the crankshaft seal surface. I contacted Rich and who realized that his new manufacturing process was off by a few thousands due to the hardening cycle done to newly used DOM tubing vs previously used welded. To get to the point, he took extremely great care of me- answered emails very quickly, shipped and provided return shipment with no hassle. His tools are quality overbuilt to say the least. his link is below.

http://www.richardsoutboardtools.com/

 

[Daveparm]

I am currently working in a 72 evinrude 6 and I just wanted to make sure I understand this carbon seal thing right. The carbon seal on this motor has a squared off rubber grommet/oring In a recess of the carbon seal. The replacement oring in is typical cylindrical shape. Was the oring squared off due to wear? Basically what I'm asking is: Is the oring stacked on top of the seal, or is it mounted in the recess inside it? Thanks

 

[Daveparm]

A picture,says a thousand words, so looking at the red arrow, does the oring go inside the seal or on top of it?

 

[F_R]

O-ring goes in the recess, and the carbon part rotates against the flat side of the plate above it. Put a drop on oil on it where it rubs. The o-ring and the carbon rotating against the plate is what completes the sealing action. And all is in vain if the gasket is not 100% good. You ought to glue the gasket to the top of the seal plate to keep the plate from rotating or the gasket from mooshing out. Use any good gasket sealant that dries hard. Scotch #847 is the recommended stuff if you have it, but not written in stone.