1982 Johnson 15 HP repair

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CMOS
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1982 Johnson 15 HP repair

Post by CMOS » 31 May 2019, 15:14

Howdy All,

It's been a while since I worked on this motor but it's time to dig into it once and for all. Here's a link the the old thread: viewtopic.php?f=4&t=42830&start=30

Today I managed to pull the power head, which to my surprise lifted right off with little or no difficulty. The original problem with the motor is that once I got it running, after about a minute the lower cylinder fouled with water. I plan to pull the head and check its surface.

Is there another possible cause for water fouling on that lower cylinder that I should look into while I have it on the table? Pappy, you still here?

I also need help and suggestions as to what needs to be replaced, in addition to what will fix the above main issue? Gaskets, grommets? Which ones?

Thank for any help. I am somewhat of noob so please be specific in any suggestions you may have.

Some random pics below:

CMOS
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20190531_134504.jpg
20190531_134236.jpg
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 01 Jun 2019, 22:07

Possible sources for water intrusion into one or both cylinders can be:
Cylinder head gasket
Exhaust cover side gasket
Cold running engine operating in cold water. More prominent during low speed operation. Lack of thermostat. Probably not your issue. Good time to replace the thermostat though while the powerhead is off. After all it's only 37 years old.....

Go back to the original post. In there I mentioned the need to replace both grommets for both water tubes. Once installed you can cut them flush with a razor knife.
Replace all Fuel lines (with good quality line) while in there and lubricate the shift linkage.

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 02 Jun 2019, 09:39

Pappy wrote:
01 Jun 2019, 22:07
Possible sources for water intrusion into one or both cylinders can be:
Cylinder head gasket
Exhaust cover side gasket
Cold running engine operating in cold water. More prominent during low speed operation. Lack of thermostat. Probably not your issue. Good time to replace the thermostat though while the powerhead is off. After all it's only 37 years old.....

Go back to the original post. In there I mentioned the need to replace both grommets for both water tubes. Once installed you can cut them flush with a razor knife.
Replace all Fuel lines (with good quality line) while in there and lubricate the shift linkage.
Thanks Pappy. That's what I was looking for - those 2 grommets. I will also replace the exhaust baffle plate gaskets and inspect that inner plate for any possible pin-holes.

CMOS
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 24 Oct 2019, 15:57

Back on this now that it's a bit cooler.

Today I pulled the Bypass cover just to take a peek at the piston walls on that side. Both looked equal and no scoring of any kind. Repainting the cover while I have ti off...

I also replaced the Head Gasket after I resurfaced the Head seal surface with 3 different grits of sandpaper. Seemed to be in pretty good shape planarity-wise. Note when I removed the Head: I did previously replace the Head Gasket on this motor when I first got it, but I did so with the Power Head on the main lower assembly, meaning most of the Head Bolts were tightened by a wrench, with no specific torque other then "feel". When I removed the Head Bolts today it was obvious that the lower bolts 2 were definitely not as tight as the middle and upper pair. Used a good torque wrench this time to 20 FT/LBS. Hopefully this will fix the problem.

Note to @Pappy: the T-stat was already new as I replaced it when I first got this motor. FYI.

Tomorrow I hope to pull the Outer and Inner Exhaust covers to inspect them. I already have replacement gaskets.

One step at a time . @Pappy

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after resurfacing...
after resurfacing...
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 24 Oct 2019, 22:37

Get your grommets and replace both of them while there. Check your surfaces on the exhaust. Did you see evidence of water on the piston top? I don't see a photo or any mention of it. You are doing fine and well on your way to a successful service on this engine. Once you have your grommets in place take a razor blade and cut the tops off the grommets that stick above the casting. You will see what I am talking about.

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 25 Oct 2019, 06:55

Pappy wrote:
24 Oct 2019, 22:37
Get your grommets and replace both of them while there. Check your surfaces on the exhaust. Did you see evidence of water on the piston top? I don't see a photo or any mention of it. You are doing fine and well on your way to a successful service on this engine. Once you have your grommets in place take a razor blade and cut the tops off the grommets that stick above the casting. You will see what I am talking about.
@Pappy

Pappy, I do have the grommets already. I will work on those after I finish the Exhaust Cover inspection and gasket replacements.

What do you mean about the above comment in Red?

Thanks for your help.

CMOS
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 25 Oct 2019, 09:45

For flatness should you see a gasket failure.

CMOS
Posts: 353
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1982 Johnson 15 HP repair

Post by CMOS » 25 Oct 2019, 12:27

@Pappy

Exhaust covers off. Nothing striking that I can recognize. Pappy? Anything look out of ordinary?

Note where my thumb is pointing in the one pic. That's a small circulation hole that was plugged with some minerals/junk.

Right now I have the Outer and Inner cover plates soaking in gasoline so I can soften up the old gaskets for removal.

Lastly, I forgot to put some type of gasket sealant on the Head Gasket. Is that a requirement???

CMOS
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20191025_111037.jpg
20191025_110939.jpg
20191025_110759.jpg
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 25 Oct 2019, 19:20

If the head gasket was a "shiny" one then nothing is needed. Usually those had a clear plastic coating you had to peel off but not always.
If it was plain and porous then yes, OMC Gasket Sealer is recommended.

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 25 Oct 2019, 19:24

Pappy wrote:
25 Oct 2019, 19:20
If the head gasket was a "shiny" one then nothing is needed. Usually those had a clear plastic coating you had to peel off but not always.
If it was plain and porous then yes, OMC Gasket Sealer is recommended.

It was OMC, with the metal inserts....

Any comments on the pics above? Normal?

CMOS
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 26 Oct 2019, 11:42

I do not see anything unusual from this end.
Change all your fuel lines while you have the powerhead off. Lots easier. Also change the overboard indicator line as that can be a bit of a pain when the powerhead is in place.
Good time to lift the lower pan off and do a good deep cleaning of the pan and mid-section.
Lube the shift linkage while the powerhead is off. Carb job if needed as well.

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 26 Oct 2019, 11:47

Pappy wrote:
26 Oct 2019, 11:42
I do not see anything unusual from this end.
Change all your fuel lines while you have the powerhead off. Lots easier. Also change the overboard indicator line as that can be a bit of a pain when the powerhead is in place.
Good time to lift the lower pan off and do a good deep cleaning of the pan and mid-section.
Lube the shift linkage while the powerhead is off. Carb job if needed as well.
The carb was previously done (full kit) by me but since it has been sitting for many months, I do plan to pull the carb and clean all the jets and various channels again. Probably gummed up a bit after sitting so long That carb is pretty easy to do (and that says a lot since I'm a general noob).

Thanks for your suggestions. Today I will pull the Exhaust Tube and those 2 water tubes.

CMOS
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

CMOS
Posts: 353
Joined: 12 Nov 2014, 11:32
Location: Magnolia, TX

1982 Johnson 15 HP repair

Post by CMOS » 26 Oct 2019, 12:34

@Pappy

Done with the exhaust main tube. It went well. The grommet on the short water tube was getting pretty dry and brittle. I got it off the tube in pieces. The other still looked pretty good and was still flexible. Both were replaced.

Right now the only thing I am missing is a Bypass Cover gasket, which has been ordered and on the way. A few days ago I decided to take off the Bypass Cover just to take a peek at the piston walls. Look good.

So, as soon as that gasket arrives I'll button that up and begin to install the Power Head on the Lower Unit. Not looking forward to that . . . .

Once the Power Head is in place and secured, then I'll do the Carb, just before installing the pull stater assembly.

CMOS
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20191026_112249.jpg
New grommets installed and trimmed.
New grommets installed and trimmed.
1982 Johnson 15 HP - in pieces, in progress
Currently boatless :(

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Pappy
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1982 Johnson 15 HP repair

Post by Pappy » 26 Oct 2019, 18:11

Do the carb now! Super easy while the powerhead is off. Don't forget to disassemble the throttle linkage completely while there as well and clean and lube that as well. There is a trick to getting the vertical one out. You should be able to figure it out pretty quick as good as you are doing already.

Newtosa
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1982 Johnson 15 HP repair

Post by Newtosa » 27 Oct 2019, 10:53

Here is the reference I've used for sealers and lubes. Looks like you're doing great, good luck.

https://forums.iboats.com/forum/engine- ... alers-list

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