1972 25 HP Johnson Outboard

This topic has 42 replies, 14 voices, and was last updated 3 years, 4 months ago by fleetwin.

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November 26, 2020 at 1:44 pm #221642
Evinrude 25
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I found a 1972 25 Hp Johnson outboard in good cosmetic condition but it was seized from sitting (the owner told me that it sat too long so the piston got seized up). I think I could be able to un-seize it but may need to get a new set of ring. 385349 — RING SET, STD, PRESS BACK. USED ON MODELS WITH PRESSURE BACK PISTON RINGS. Most places don’t have them. Google up E-bay, the cost is almost $100 per set.
I find the 0383473 available but this ring for a standard piston without press back. I got a bit confused. So if I want to use this ring, I have to replace the piston? Please advice! I like to add 25 Hp to my collection but the cost of the new ring and its availability sets me back to purchase the outboard.
November 26, 2020 at 2:24 pm #221645
frankr
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US Member - 1 Year (includes $3 online payment fee)
Pressure back rings require different ring grooves. So, they are not compatible with non-pressure back pistons.. I guess you already know that 25hp pistons are different than 18-20hp pistons, right?
November 26, 2020 at 4:28 pm #221650
Evinrude 25
Participant
Just learning now. By looking at the part number, 18 hp and 20 hp share the same stuff but 25 hp has different part (pistons, rings). They are NLA parts. I am not sure if I want to work on it.
November 26, 2020 at 9:05 pm #221671
bobw
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I went through this same issue when I restored a 1972 Evinrude 25hp a few years ago. You might take a look at the motor serial number before you decide whether you want to pick this motor up or not. Pressure back pistons and rings were used on all 25hp motors built after serial number 25202-01791 with all motors before that number using standard pistons and rings. I did a lot of shopping around and finally managed to find a set of NOS 385349 rings for around $30 per set.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
November 26, 2020 at 9:08 pm #221672
crosbyman
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Canada Member - 2 Years
have you pulled the cyl head and looked at the walls . if ok why not just soak the pistons with some atf or marvel oil for a few days the try to rotate the flywheel or…used a wood peg and persuation to alternately give it a few wacks on each cyl.

resoak and try in a few more days

my 9622a 9.5 freed up nicely and has been running great for several years now

run some engine cleaner / decarb and run some 25/1 mix

it may be all it needs .. see utubes change the impeller gearcase oil etc…

Joining AOMCI has priviledges 🙂
- This reply was modified 3 years, 4 months ago by crosbyman.
November 26, 2020 at 10:11 pm #221679
Evinrude 25
Participant
It is actually 1973 since the model #25E 73 A and the serial number C 19189. It has two external coils which I have learnt from my 1973 20 hp about low tension ignition system. So from this serial number, could you tell if it has standard pistons? If not, could I convert it to standard piston or look for a good used standard piston from other models?
November 26, 2020 at 10:26 pm #221680
bobw
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US Member - 1 Year (includes $3 online payment fee)
All of the 1973 25hp motors used the 385349 pressure back rings and pistons. As crosbyman noted, it might not be stuck real bad and if you can free it up easily, that might be all it needs. My ’72 motor was rusted up but came free with about 6 hours of soak time and a little rocking of the flywheel. The rings were not in bad shape but I just replaced them after tearing it down to hone the cylinders. If nothing else, you should be able to negotiate a lower price for a stuck motor.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
November 26, 2020 at 10:39 pm #221681
ede
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US Member - 2 Years
I do have several sets of NOS 385349 piston ring Ed Elliott eddelliott@cox.net

1 user thanked author for this post.

vintin
November 27, 2020 at 1:10 am #221683
reivertom
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US Member - 1 Year (includes $3 online payment fee)
First try to un-stick it. It may just be old oil and gas gunked up in the cylinder.
November 27, 2020 at 7:58 am #221684
Evinrude 25
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Hello Ede,
I keep in mind that you have it. I will contact you when I need them.
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