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1978 evinrude 112/115 losing cylinder 4 consistently - 115899c

S

Stev0623

New member
Just picked up this motor off marketplace for around $300 with rigging and steering. Got it installed in my boat. At first it wouldn't start without spraying fuel mix into the carbs. Once started it seemed to run ok but would consistently be idling on 3 cylinders.

Compression test shows 120-125 across all 4 cylinders. I noticed the motor had a hodge podge of mismatched parts on it so I've replaced the following with genuine OEM parts:

4 spark plugs
4 ignition coils
4 coil wires
2 power packs
Rebuilt carbs with oem carb kits. Float is set to even with the bowl.

The motor will now start without spraying fuel into the carbs but I'm still having the same idling issues. Motor will idle normally for a few seconds and then it will bog down. It usually stays running on 3 cylinders but sometimes it dies. This seems notable because I feel like this motor should still idle on 3 cylinders. I can pull the wire off cylinder 4 with no change to engine performance at idle. With plug wire reinstalled I'm able to Rev freely through the rpm range without misfiring. I've tried to swap the new parts between cylinders to see if the problem moves but it appears to be isolated to cylinder 4. I've used a timing light to verify that I still have spark when it starts to bog at idle. When pulling plugs after running they all appear to be very similar. I was expecting to maybe find that #4 was fouled out but that's not the case. I inspected the reeds with a scope and they look to be in good shape.

Note that I'm not an outboard mechanic but I paid my way through college by turning wrenches so I'm pretty handy. I picked up the online seloc manual but to be honest it's not very useful. I'm in search of a better shop guide
 
racerone said:
High speed jet in the very bottom of the float bowl is clean / not plugged ?
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Thanks for the reply!

I used a set of wire brushes along with choke cleaner and compressed air and was able to run it freely without noticing anything left in there. Carbs look spotless, however I keep leaning towards fuel delivery since I know I have compression and spark.

My biggest question I keep asking myself (and anyone who will listen) is; if it was a carburetor issue shouldn't it be causing an issue on cylinder 2 and 4 and not just 4?

Thanks again,

Steve
 
Nope----Your motor has 4 separate crankcases.----Each one fed by one barrel of the carburetors.------Checked the fuel pump diaphragm as it may be ruptured.----Easy to replace the diaphragm.-
 
racerone said:
Nope----Your motor has 4 separate crankcases.----Each one fed by one barrel of the carburetors.------Checked the fuel pump diaphragm as it may be ruptured.----Easy to replace the diaphragm.-
Click to expand...
Thanks again for the reply. I forgot to add to the original post that I added an OEM Johnson fuel pump as well.

I'm on the way home from my son's football game and will tear that carburetor apart when I get back. Hoping to get on the water tomorrow afternoon but been getting my business handed to me by this issue.

Thanks,

Steve
 
Perhaps you bought a motor with someone's head ache.-----Did you do a compression test yourself ?----Have you looked into issues with crankcase compression ?----Checked flywheel key ?
 
racerone said:
Perhaps you bought a motor with someone's head ache.-----Did you do a compression test yourself ?
Click to expand...
Yes I did as recently as this morning. He showed compression with his tool when I purchased but for peace of mind I got my own tester today and tried

Thanks,

Steve
 
Well, I got home from my son's football game and jumped into the carbs again. Upon inspection they were all clean with no debris noted. All jets are flowing really well with carb/choke spray. Double checked for vacuum leaks and couldn't find any. Went ahead and inspected the reeds and they all appear to be functioning correctly.

I'm still open to suggestions. Much appreciated.

Thanks,
Steve
 
It being a 1978 I would pull the head and inspect.(high ring pistons) Seen many motors with good compression and bad cylinders
 
Hey guys thanks for the replies.

Took the boat out this morning because I'm glutton for punishment. Currently docked at the island about to grill. After idling at the ramp for about 10 minutes the misfire seems to have gone away.

Hit the channel and went to throttle up and I achieved about 2,300-2,500 rpm. Boat won't move above 11mph. No audible misfires heard but almost nothing for power. Thoughts?

Thanks, Steve
 
You have replaced a bunch of parts on a hunch.----Time to do some trouble shooting.---Answer questions.-----Check flywheel key.----Does spark jump a gap of at least 3/8" on each lead?----Post actual compression values for each cylinder.----Wires from powerpacks going to the correct coil ?-------Water in the fuel ?
 
racerone said:
You have replaced a bunch of parts on a hunch.----Time to do some trouble shooting.---Answer questions.-----Check flywheel key.----Does spark jump a gap of at least 3/8" on each lead?----Post actual compression values for each cylinder.----Wires from powerpacks going to the correct coil ?-------Water in the fuel ?
Click to expand...
Thanks you for taking the time to keep responding and offering routes to go. I will respond to these questions tomorrow or Tuesday when I have a chance to get back into the motor. You rock.

Thanks, Steve
 
racerone said:
You have replaced a bunch of parts on a hunch.----Time to do some trouble shooting.---Answer questions.-----Check flywheel key.----Does spark jump a gap of at least 3/8" on each lead?----Post actual compression values for each cylinder.----Wires from powerpacks going to the correct coil ?-------Water in the fuel ?
Click to expand...
Sorry it took so long to get back to you. I got sent out of town for work and today is my first free day back at home (and of course I decided to get frustrated with it).

I pulled the flywheel this morning. Key is intact. I didn't notice any of the plastic underneath it (around the stator) to be melted or cracking. I did notice some metallic/magnetic shavings on the flywheel. I cleaned them up just to be safe. I did not notice any broken or cracked wires - however I did not remove the stator and go any lower.

Using a spark tester with adjustable gap I could confirm that all cylinders had spark that was willing to jump 3/8th of an inch with no issues. Cylinder 2 and 3 were actually able to jump closer to 1/2 inch.

Compression was as follows;
Cylinder 1 - 118 psi
Cylinder 2 - 119 psi
Cylinder 3 - 119 psi
Cylinder 4 - 120 psi

The wires on the power pack seem to be somewhat length oriented. The wire that goes to cylinder 2 seem like it would be a tight fit to reach cylinder 4 and the wires from cylinder 4 would have excess slack if connected to cylinder 4.

I have an attwood water separator, so I assume that would prevent water from getting through, but I will be hooking up a second gas can today. Wouldn't water in the gas theoretically cause issues on all 4 cylinder drop test and not exclusively cylinder 4?


Thank you so much,

Steve
 
Inspected high speed jet in the very bottom of the float bowl ?----Did you inspect diaphragm in fuel pump ?-----Perhaps look into issues with crankcase compression as well.-----And on this motor each carburetor bore feeds one cylinder.-----Bottom carburetor feeds 3 and 4.----Bottom carburetor has nothing to do with top 2 cylinders.-----Stop running this motor until you sort this out.----If one carburetor jet is plugged it will starve one cylinder of fuel.----And the oil that is in the fuel.----Will lead to an empty wallet !!
 
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