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Hello everyone,
I am newbie to the boating world and have recently picked up a nice lil jon boat with a sweet '72 Johnson 4hp on it. In my attempt to tune it up, i failed to insert the copper tube into the impeller housing and i overheated and seized the motor up. (about 4-5 times, i thought a had a fuel/carb issue)
I have fixed the issue(inserted the copper tube), and the motor runs very smooth (new plugs, rebuilt carb, rebuilt fuel pump, new gear oil, new impeller), and i have water spraying out of the exhaust holes on the shaft housing.
I checked my compression and this is were it gets bad. top cylinder barely hits 30lbs. and the bottom one is about 18-20lbs.
I have recently ordered and changed out the head gasket. the cylinder walls did not appear to be scratched or damaged, but the gasket was paper thin, and almost cracked and crumbled coming off. I lightly sanded (on a flat surface) the head in a figure eight pattern to take down any high spots, and once all surfaces were clean i stopped. i noticed that in-between the pistons the small piece of metal was low compared to the outside of the cylinder head. I stopped sanding once that low area became clean.
The new gasket has been installed, and i rechecked the compression (without running it first) and i didn't see much if any change yet. Should i see a difference right away? Do i need to start and get the motor at operating temp and then recheck? (after i double check torq specs? )
Is it possible that because i sprayed and wiped the cylinder walls with wd-40 and it's just highly lubricated?
It's been raining the past few days and i haven't started or ran the motor at all since the gasket was replaced.
My next question is what can (cheaply) to gain more compression in this lil motor? replace the piston rings? get a honing tool and score the surface of the cylinder walls? Any tips or suggestions would be greatly appreciated.
I am really kicking myself in the @$$ for injuring this lil guy. and i want to do my best to revive it, without having to go to a machine shop, purchasing oversized rings, etc....
Thanks in advance for the help!
Tpot
I am newbie to the boating world and have recently picked up a nice lil jon boat with a sweet '72 Johnson 4hp on it. In my attempt to tune it up, i failed to insert the copper tube into the impeller housing and i overheated and seized the motor up. (about 4-5 times, i thought a had a fuel/carb issue)
I have fixed the issue(inserted the copper tube), and the motor runs very smooth (new plugs, rebuilt carb, rebuilt fuel pump, new gear oil, new impeller), and i have water spraying out of the exhaust holes on the shaft housing.
I checked my compression and this is were it gets bad. top cylinder barely hits 30lbs. and the bottom one is about 18-20lbs.
I have recently ordered and changed out the head gasket. the cylinder walls did not appear to be scratched or damaged, but the gasket was paper thin, and almost cracked and crumbled coming off. I lightly sanded (on a flat surface) the head in a figure eight pattern to take down any high spots, and once all surfaces were clean i stopped. i noticed that in-between the pistons the small piece of metal was low compared to the outside of the cylinder head. I stopped sanding once that low area became clean.
The new gasket has been installed, and i rechecked the compression (without running it first) and i didn't see much if any change yet. Should i see a difference right away? Do i need to start and get the motor at operating temp and then recheck? (after i double check torq specs? )
Is it possible that because i sprayed and wiped the cylinder walls with wd-40 and it's just highly lubricated?
It's been raining the past few days and i haven't started or ran the motor at all since the gasket was replaced.
My next question is what can (cheaply) to gain more compression in this lil motor? replace the piston rings? get a honing tool and score the surface of the cylinder walls? Any tips or suggestions would be greatly appreciated.
I am really kicking myself in the @$$ for injuring this lil guy. and i want to do my best to revive it, without having to go to a machine shop, purchasing oversized rings, etc....
Thanks in advance for the help!
Tpot
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