Logo
FULL SITE MENU

Johnson 3.5 2hp Compression

T

Tony Outboard

Contributing Member
Does anyone know what the OEM compression should be, I have 80 psi on a cold engine post rebuild, I have a manual but it's vague as hell and doesn't give me an expected figure. Anyone have any clues?
Thanks
Tony
 
timguy said:
If you have faith in your gauge, that is a good reading.....2hp?
Click to expand...
Well it's a weird one really. has a 3.5 sticker and also made in PRC but the data plate sticker has been deliberately nulled with loads of sort of figure 8 etchings, done properly, it's not some baddun has tried to delete them, I'm comfy with anything 70psi + cold but just wondered what the book figure should be. From the service manual " Since Bombardiers takeover Johnson has started to publish cylinder comp px specs for 4 strokes" (I know mine is obvs 2 stroke) but I would have thought the factory spec would be published some where, comically, now I have good comp and a spark thought I'd move on to the carb and never seen such a POS in my time. ;)
 
I rebuilt a single cylinder Yamaha last summer and it put out 100....but that was a 5 hp. I think you are okay with the 80 psi. I have never seen exact published compression on outboards of this earlier era.
 
That's old friend "Farmer" who helped run the camps, retired heavy equipment operator for a Hibbing MN iron ore mine. He became the Grandfather I never had. Lived to be 82. That's me, operating the 16' Cadillac with Mark 30 and 6 horse Fisherman for trolling. Lower Manitou L. about 45 miles north of Ft. Francis Ontario....accessed only by plane in those days....1976. Still have everything in that picture......except old "Farmer"....6'4" 250 pounds. He was one cool dude.
 

Attachments

  • IMG_20200322_130314668~2.jpg
    IMG_20200322_130314668~2.jpg
    217.2 KB · Views: 38
Last edited:
Nice Fishing reel you have with you on the boat. Is it Abu Cardinal serie? I have Abu Cardinal 77x with pole, but never used. If i remember right, both are from year 1977.
 
Good eyes, my friend. It's a US made True Temper model 923 C. Spooled with 45 lb. test woven stainless. We troll deep for Lake Trout, maintaining a speed of 2 mph. Biggest trout was caught by "Farmer" pictured. 13 kilos.....probably 25 meters deep. Do have some treasured ABU lures and reels, use them on special occasion.
Note to OP. I have an Onan generator at one camp. It has those similar stampings over a serial number. It was originally provided to an Onan employee for his personal use, it had some experimental modifications.
 
Back
Top