1954 johnson cd-10 5.5 hp low compression?

Ray2

Cadet
Joined
Sep 26, 2010
Messages
16
hi guys,my motor checked 30 psi on both cylinders and would not stay running,so i took advice from here and put new carb kit,head gasket,all new fuel lines and filter plus sanded head on glass, plus put motor up and poured sea foam down both cylinders and let soak for over 8 hours,then checked compression again and at still says 30 psi on both cylinders,so i pull and pull some more and it finally starts,this time for about 4 or 5 minutes and then dies,by this time both my arms are worn out so i'm wondering if the rings are bad,when i took the head off some one had already decarbed it, it was clean,so i'm thinking the guy i bought it from knew it had low compression,but would it even run at this low psi,i put my thumb over both plug holes and turned it slowly and it does have suction,any thoughts,thanks...
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1954 johnson cd-10 5.5 hp low compression?

If the mtr has intake and exhaust side covers, remove them and check your pistons and rings. May want to try a different compression gauge also.
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 1954 johnson cd-10 5.5 hp low compression?

If it ran for 4-5 minutes, it has enough compression to start and run. As boobie suggested, try another compression guage.
What do you have the low speed needle set at, 1 1/4 turns out from lightly seated?
 

Ray2

Cadet
Joined
Sep 26, 2010
Messages
16
Re: 1954 johnson cd-10 5.5 hp low compression?

thanks guys, the gauge is the screw in type with a o-ring so you wont screw it in too far and hit the piston,its a rental , oem is the brand name,same as the first time,iwould screw it in until its snug and pull 5 to8 times with and without other plug in other hole,any tighter i would be afraid it would hit the piston,can this motor run on 30 psi? low speed needle is about right,i had it at 1 1/2 then turned in intil it smoothed out alittle,i got it in a plastic garbage can so it moves around a bit,if i can get it to run better will take it to lake for finale adjustment,its very hard to start wright now,what would i be looking for when i take off exhaust plate? as you can tell i've never messed with an outboard before, it felt real good when it started thanks again for the good advice, i'm learning alot..
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: 1954 johnson cd-10 5.5 hp low compression?

I would be looking for a blown gasket between the cylinders.
 

Ray2

Cadet
Joined
Sep 26, 2010
Messages
16
Re: 1954 johnson cd-10 5.5 hp low compression?

how would you check that,i put a new head gasket on,i put head on flat glass and sanded in circle motion till shinny, i was thinking the same sense it has the same compression
 
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