Low Compression 72 Johnson 50 HP

ziggy101

Seaman Apprentice
Joined
May 24, 2007
Messages
35
I have had my boat in my garage for about 12 years without running it. I got it out this year and got the motor started, but to keep it going i revved it up on a muff (not in a tank) which i now understand is a bad idea, but it started and ran. took it out on the lake connected to a gas tank somene gave me. used about whole tank of gas stopping and starting. after a while the motor ran rough and stalled as i tryed to put it gear and had to take cover off and give it gas to keep it stalling at shift. when i got back to the dock i noticed the tank was sucking in as it was not vented, and i assumed this was why it was running rough.

i tryed it again a couple weeks later and i could not get it started, not even sounding like it was firing.

took it home and read my manual, said i should check compression before tune up. I did and got 175psi on bottom and 10 psi on top.

i have been reading some of the postings about decarboning foam, putting oil in the cylinder etc - i am wondering if there is something to do before i tear this apart so i might not have to??

Also if i do tear it down where can i find rings and other parts for a motor this age - did some searching on web and could not find any, including iboats.

is this motor worth trying to fixing? :confused:
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,392
Re: Low Compression 72 Johnson 50 HP

Sounds like the top cylinder could have starved of fuel / oil mix causing damage to the cylinder and rings. It has to run to decarb it with seafoam. For the heck of it take off the cylinder head and check the bores and also make sure that the cylinder head gasket was not leaking out.
Just my opinion and some experts will be along shortly.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,392
Re: Low Compression 72 Johnson 50 HP

And by the way it is worth fixing in my opinion.
 

ziggy101

Seaman Apprentice
Joined
May 24, 2007
Messages
35
Re: Low Compression 72 Johnson 50 HP

KenMyFam:
thanks for the advice. I was not meaning to post the same thing twice. Thick fingers.

do you have an idea where i can find parts for this motor?
 
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