Older Johnson, serial number on the welch plug ?

[seanymphken]

I am trying to decipher the year and horsepower from the numbers I have on this johnson outboard motor I am working on. The numbers are taken from the welch plug on side of motor. The numbers are J2784949. Can anyone convert this for me ? Is there a web site or chart on line that shows the number conversions ? Please Help, thank you !!!

 

[tashasdaddy]

Re: Older Johnson, serial number on the welch plug ?

thats a serial # need model #.

 

[seanymphken]

Re: Older Johnson, serial number on the welch plug ?

Someone put this motor in an Evinrude model number 6705M. I do know this is not the correct motor for this outboard application. Through research I do know that you can find out the year and horsepower from the serial numbers on the welch plug/ per Johnson and Evinrude. I also know that the J in the serial number refers to Johnson. Can anyone else please help me convert these numbers, J2784949. Does anyone know of a number conversion chart online to decipher this type serial number ?

 

[ezeke]

Re: Older Johnson, serial number on the welch plug ?

You would have to get a BRP dealer to pinpoint the serial number. I can tell you that it falls between known serial numbers from 1967 and early 1968.

 

[seanymphken]

Re: Older Johnson, serial number on the welch plug ?

How did you come up with 1967 or 1968 ? Thanks ezeke !!!

 

[ezeke]

Re: Older Johnson, serial number on the welch plug ?

"How did you come up with 1967 or 1968"

"I can tell you that it falls between known serial numbers from 1967 and early 1968." - My own motors.

 

[seanymphken]

Re: Older Johnson, serial number on the welch plug ?

Great, thanks for the info. I apprieciate the knowledge and for you answering so quickly. Do you do any mechanical work on these motors / older Johnson's or Evinrudes ? I checked out the compression and it is 65 psi on both cylinders. Assuming its a 6 hp, is that good enough compression to go any further with and tune it up ?

 

[CATransplant]

Re: Older Johnson, serial number on the welch plug ?

Try another compression guage. Since the cylinders are equal, I'm betting you'll be able to get this running fine as is. Getting good compression figures on small rope start outboards isn't that easy. If it's been sitting a long time, the rings may be a little sticky, too.

Get her started, then give it a good decarboning with Seafoam and then run it for half an hour or so at a fast idle in a barrel. Check the compression after that. It'll be higher.

Those little 6hps are workhorses. They seem to last forever, and everyone and his three brothers have them.

 

[ezeke]

Re: Older Johnson, serial number on the welch plug ?

That is enough compression if the cylinders are within 10% +/- of each other. Compression may improve if you de-carbon the engine. It should improve some if tested after running and still warm.

I have always done all of my own outboard work except for boring engine blocks. I work on some of my family's motors now that I am retired. You should probably follow the "Awakening a Sleeping Outboard" thread in the Engine FAQ Forum:
http://forums.iboats.com/showthread.php?t=158086

I have a 1965 6HP which is not very different. I would put in a new water pump, relace the fuel lines, add new gear oil and update the spark plugs. The old fuel lines are not alcohol resistant.

http://www.evinrude.com/en-US/About.Us/FAQ/Oil.Fuel.htm

http://www.boatsetup.com/SparkPlugChart.pdf

 

[c-5 aircraft mechanic]

I have an older Johnson and the welch tag is G3951107 any idea what year it would be???

 

[jimmbo]

Post few Pictures of it, there are a few on here that are pretty good at Cowl Graphics