1994 Johnson 112 compression and fuel delivery question

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
Hi to all and thanks to everyone for your help with the last issue.

A little history. I bought this boat motor and trailer that has been sitting for a few years. The motor is 1994 Johnson 112. I was and am still having a fuel delivery issue. I am pretty sure I have narrowed that to the fuel pump from the following.
Rebuilt carbs.
Replaced plugs
Replaced primer bulb.
Added clear inline fuel filter between bulb and motor.

I can pump the bulb and see the fuel filter fill up. I can start it and watch it run until the carb bowls empty and it does not draw any fuel from the filter.

Now to the more important issue. Compression.

Cylinder 1 90lbs
Cylinder 2 90lbs
Cylinder 3 20lbs
Cylinder 4 90 lbs

My question is what could be the cause besides broken rings and does anyone have either a schematic or a manual for this motor.

I am not going to take it to a shop as I am by nature a do it yourselfer. I like to learn things, make sure they are done right and get a great satisfaction from doing things myself. I don't have a lot of experience with outboards but I am prepared to tear into it.

I do currently have the tank half full of fuel with sea foam. Is there something wrong that running it with sea foam could possibly rectify. I.e. A stuck valve? Thanks for all of your input in advance.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
Step # 1 is to remove the port cylinder head.-----Oh so common to find the broken ring damage on top of the piston.-------Sounds like a complete teardown is in order.-------And no such thing as a stuck valve that can be the issue of low compression.-----Not even a broken / missing reed valve will cause low compression.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Pull off both heads, with 20 PSI in one cylinder it means you're inline for a total rebuild.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
outside chance you could have a stuck ring, as the engine has been laid up for quite a while. You might pull the plugs and rotate the the flywheel until the bad cylinder is at TDC (Use the eraser end of a pencil to determine that.) If you can get the engine horizontal or nearly so, pour in some ATF and let it soak.
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
On a side note/question. Assuming I am lucky enough to have stuck rings and not broken, Is there an operational error that would cause this? What I mean is this. Is there something that should have been done that wasn't to keep it from happening. I am visioning rings on the #3 piston to be rusted or carbon stuck. how could I prevent this in the future?
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
I see a lot of guys using Marvel and other such products for stuck rings online. My question would be can anyone see an issue with trying Berryman's Chem dip in the cylinder? this stuff really did a number on cleaning the carbs so I thought maybe it would do a job inside the cylinder also? Thoughts??
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
Pull off the head and look at it.


as I already stated. I will be pulling the head this afternoon. I was just asking some preemptive questions before I do so I have an idea of what I want to do in the event I find stuck rings.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
When storing an outboard, fogging oil is a standard precaution. A stuck ring could be a result of water intrusion (even humidity), and it can result from carbon build up. Marvels and Berrymans and Seafoam are aggressive -- imo not needed for regular use, and have to be careful if using it to soak. Soaking with ATF might save a teardown, and will do no harm. A broken ring is what it is, of course.
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
When storing an outboard, fogging oil is a standard precaution. A stuck ring could be a result of water intrusion (even humidity), and it can result from carbon build up. Marvels and Berrymans and Seafoam are aggressive -- imo not needed for regular use, and have to be careful if using it to soak. Soaking with ATF might save a teardown, and will do no harm. A broken ring is what it is, of course.


Thanks Oldboat1 I appreciate your input. I believe you are right and it is probably a broken ring. No harm in hoping for stuck I suppose. I am curious, When I pull the head, will I be able to see the rings well enough to see if one is broken or will I have to pull the piston to see that? I think If I wont be able to see the ring well enough to tell then I may try the ATF soak just for good measure and if it doesn't work then just go ahead and tear into it.

Again, Thanks for your input.
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
No Title

The verdict is in... it was, as suspected by all, a broken ring. Not only broken but gone. Luckily no visible damage to the cylinder wall. The piston however obviously hammered on the ring as it was exiting the cylinder. it apears to have nicked the top edge of the piston terribly as seen in the photos. My question is this then. should I file down the nicks on the piston or just replace it as I put new rings in. I don't mind doing so I just don't want to waste money if filing it smooth would be just as good. You can see the exhaust port in the photo where it hit the ring on exit. this nick does not appear to be rough in any way inside the cylinder. Hone the cylinder and replace the piston and ring??
 

Attachments

  • photo257785.JPG
    photo257785.JPG
    146.9 KB · Views: 0
  • photo257786.JPG
    photo257786.JPG
    99.8 KB · Views: 0

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
2 more questions if you don't mind.

1,Before finding this problem it was VERY hard to start. would being down 1 cylinder make it incredibly hard to start, as in almost impossible, or just a little stubborn. I am thinking that this may solve a LOT of the problems I was having.
2, I was showing 90lbs on compression test on other 3 cylinders, is this an acceptable number for this motor?
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
sorry, dreese. Too slow in checking back. Think with a replaced piston and some running, the others would improve. 90/95 - 100 all around should be acceptable (imo).
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
sorry, dreese. Too slow in checking back. Think with a replaced piston and some running, the others would improve. 90/95 - 100 all around should be acceptable (imo).


Thank you so much. oldboat1

I plan on buying a manual for this motor but just curious if anyone knows what the head torque and pattern is on this motor. Are these considered stretch bolts that must be replaced or re-use the original head bolts?
 

dreese2005

Seaman Apprentice
Joined
Aug 21, 2010
Messages
34
So now the million dollar question... What caused the ring to break? is this common? what can be done to prevent it?

I am guessing, and it is just a guess, poor winterizing/maintenence practice from previous owner?
 

nrf414

Chief Petty Officer
Joined
Feb 16, 2008
Messages
573
following along. my guess is could be lots of reasons but I'm suspecting the same, poor maintenance, wrong mix of a/f running lean, maybe a poor water circulation caused some overheating and ring snapped and went into piston head.
 

rothfm

Ensign
Joined
Sep 26, 2006
Messages
913
So common on these engines. No one wver seems to decarbon them. Must be done, along with care to maint.

Others will chime-in. At the minimum, you need to micrometer that bore for roundness and taper.

If in spec, and no scratches that catch your nail, a hone with replacement piston and rings can suffice. Alum transfer, if any, can be removed with muratic acid

If out of spec, you need to rebore to next size.

All the while looking towards the real culprit, fuel delivery, cooling, carbon. If you dont attempt to solve why, it may happen again.

Im a big believer in carb rebuild kits and soaking them. Peace of mind
 
Top