1994 115 Johnson Rebuild

hydra84

Cadet
Joined
Jun 15, 2010
Messages
6
I was given a 1994 115 Johnson by a family memeber, the motor was supposed to have been recently rebuilt. One cylinder had 0 to 30 PSI the rest were 120. I tore the engine apart and the piston was broken between the top of the piston and the top ring groove. The cylinder really wasn't damaged like i felt it would be. Can I replace the damaged piston and ring and leave the other 3 cylinders as is ??
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
Re: 1994 115 Johnson Rebuild

sure you can.....it would be wise to check the cylinder diameter for size, "out of round" and taper. Be sure to deglaze the cylinder as well. (make sure you determine the proper piston size "standard or oversize")
 

hydra84

Cadet
Joined
Jun 15, 2010
Messages
6
Re: 1994 115 Johnson Rebuild

I have replaced the bad piston and reaassembled the engine. The motor still has the orginal problem . It will not idle. It will start and run at about 1/4 throttle but any less and it dies out. I have rebuilt the carbs and still have the same issue it will not idle. Anyone have any suggestions on what i can try to get this thing running correctly.

thanks
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: 1994 115 Johnson Rebuild

Have you tried using the primer/choke when it is doing this and see what happens ?
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 1994 115 Johnson Rebuild

A couple of things to check. When that engine idles, the carb butterflys are closed. At idle, the engine draws fuel from special, small, idle passages in the upper carb body. If these passages get any dried fuel in them, they will restrict and not pass fuel. The engine will not idle properly. Best to clean these passages with an aerosol carb cleaner. Spray one passage in one carb, and note the outgoing spray pattern. Go on to the next carb and do the same passage-note it's spray pattern and compare to the first passages. Etc for remaining passages. Once you slightly open the carb butterflys, the engine will draw fuel from other jets and it may run fine at higher rpm's. If the idle is too low, the engine will idle poorly, may even die in gear. The engine should idle at 650 rpm +- 50 rpm. This is a spark issue, not a carb issue. Set the idle when the boat is floating in the water and in gear.
 

Haffiman

Commander
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Dec 17, 2009
Messages
2,454
Re: 1994 115 Johnson Rebuild

What is your compression readings AFTER the rebuild?
 

Solittle

Fleet Admiral
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Apr 28, 2002
Messages
7,518
Re: 1994 115 Johnson Rebuild

Did you determine the cause of the original problem?
 

hydra84

Cadet
Joined
Jun 15, 2010
Messages
6
Re: 1994 115 Johnson Rebuild

I haven't checked the compression since replacing the piston.
I also haven't determined what caused the engine to fail.
I feel it was running lean or was overheating for some reason.

I check what has been suggested and check the compression this weekend.

Thanks
 
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