Topic: 1962 Johnson 3hp Seahorse – Antique Outboard Motor Club,Inc

This topic has 15 replies, 10 voices, and was last updated 7 years ago by outbdnut2.

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April 8, 2018 at 2:33 am #9580
campcozyme
Participant
My husband and I are working on our 1962 Johnson Seahorse 3 hp and my husband was wondering if anyone on the forum would know of a source to purchase piston rings? I ordered some of our other parts from marineengine.com but it appears they don’t have the rings available.
Thank you in advance for your help.
Pam
April 8, 2018 at 3:26 am #73584
crosbyman
Participant
Canada Member
and compression numbers are….?

Joining AOMCI has priviledges 🙂
April 8, 2018 at 3:55 am #73585
Mumbles
Participant
P/N 378412 and ME is showing 10+ in stock at $75 per. A Giggle search brings up different sources with different prices. Not too long ago these were available thru my local OMC/BRP dealer for about twenty bucks each. 😥

https://www.google.ca/search?q=omc+3784 … e&ie=UTF-8

https://www.marineengine.com/parts/john … head+Group

https://www.marineengine.com/newparts/p … OMC0378412
April 8, 2018 at 11:50 am #73597
stanley
Participant
US Member
Try Dan Gano at 712.336.3297.or website: gano@ganotech.com good guy,fair price.
April 8, 2018 at 1:26 pm #73608
campcozyme
Participant
Thank you everyone for the answers. Someone asked what the compression numbers are. Sadly, they are 15 lbs for each piston. It’s been sitting for a long time. My husband sprayed penetrating oil in there and it has been sitting overnight in hopes that if something is stuck it will free up. We are going to check again today (I will keep you all posted). We will then take it apart and check the head gasket. We know 15 lbs is not good but if all was well what compression number would be good?
April 8, 2018 at 1:32 pm #73609
kevinrude
Participant
quote Campcozyme:

Thank you everyone for the answers. Someone asked what the compression numbers are. Sadly, they are 15 lbs for each piston. It’s been sitting for a long time. My husband sprayed penetrating oil in there and it has been sitting overnight in hopes that if something is stuck it will free up. We are going to check again today (I will keep you all posted). We will then take it apart and check the head gasket. We know 15 lbs is not good but if all was well what compression number would be good?

60lb would be about the minimum. Obviously, the bigger the better. Also, if something is stuck and the penetrating oil didn’t work, a mixture of 1/2 transmission fluid and 1/2 paint thinner seems to be a popular way to free things up. I’ve had success with it.
April 8, 2018 at 1:44 pm #73610
campcozyme
Participant
Kevinrude,

Thank you for that tip, just talked to my husband and we will give that a try too before we pull it apart.
April 8, 2018 at 2:00 pm #73611
cajuncook1
Participant
Pam, if both cylinders are 15psi each, then the likely culprits is the head gasket. Those head gaskets do not have fire ring protecters. Chances are there is a tear or leak from the head gasket in between both cylinders. The hallmark is low even pressure from both cylinders. Please do not tear the motor down and re-ring until you have seen the head gasket condition. Regardless you will have replace the head gasket.
April 8, 2018 at 3:04 pm #73615
outbdnut2
Participant
US Member
If the head gasket is bad, the head is likely slightly warped – which can cause headgasket breakdown between the two cylinders. To make it flat, spread out emory or wet/dry sandpaper on a solid very-flat surface (I use the flat steel table of an old tablesaw). Then rub the head on it until the sanding marks on the head are uniform, meaning it’s flat. Do not over-torque mounting bolts or warpage may occur again.
Dave
April 8, 2018 at 3:59 pm #73618
Steve D
Participant
Maybe these will help…
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