1981 115hp johnson, 3 outta 4 working

[leatherneck514]

Hello Everyone,

I'm new to this. I just bought a 1990 Cobra with a 115hp Johnson outboard attached. It was running really ruff so I started check it out an found that it is only running on 3 outta 4 cylinders. There is a sparkwhen I pull the spark plug wire off but it does not make a difference in the way the motor is running. I pulled the carbs off and cleaned them real good with high pressure marine carb cleaner, also used a small wire to push through all holes. This made it run better but it is still not firing the fuel on that one cylinder.

Can anyone recommend what to do next?

Thanks

 

[R.Johnson]

Re: 1981 115hp johnson, 3 outta 4 working

What about a spark, and compression check? What is high pressure carb cleaner, and where do you buy it?

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

If the compression results are within 15% of each other, swap the two power packs so that you can see if the problem follows the packs or stays on the same side.

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Thank you for the replies. Yes there is a spark. Yesterday, I put a new set of spark plugs on it. I pulled the carbs off again to check to see if I missed something (all Clear and clean). I pulled a few of the fuel hoses off and blew through them to see if one maybe clogged (all clear). It is running great very strong and smooth but still only on 3 outta 4. The spark plugs that I pulled off on the 3 that are working show the wear and have the wet fuel still on them; the 1 that is not working is dry and still looks fairly new, just blackened a little. I have not checked the compression yet. The carb cleaner that I was referring to is the spray can with the short tube that is made for outboard motors. Sorry if that?s not right.

Thanks again for all the help!

 

[cdoliver]

Re: 1981 115hp johnson, 3 outta 4 working

1. Check your compression. Don't do anything else until you do this.
2. Check your spark (do a search on diy spark tester)
3. you can spray pre mix into the front of the carb while it is running. If it picks up check that carb again.
4. link and sinc
I have this motor and I feel your pain

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Well i have a guy that has been working on marine engines for many many years helping me. He has said the same things that everyone on this site has told me. I checked everything over and over so i handed him the motor to look at for me. I will do the compression test when I get it back.

To the spark test I have held the spark plug wire away from the plug while it is running and it did not make a difference. When I get closer and allow the spark to jump to the plug it still does not make a difference. When I do that to the other ones the engine almost dies until I get it close and the spark connects again, then it reves back up.

I switched the carborators and manually worked the bar connecting the 2 carbs. It ran just like before so I know the carbs are clean.

I'm not sure how the computer works on this. If there is a spark then does that mean the computer is working?

If the cylinder is dry on is it getting fuel?

Which fuel line is the cylinder using to get the fuel inside the to ignite?

Is the line going into the side of the cylinder working off of pressure created by a suction?

Thanks for all the help!!!

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

You have 2, two barrel carbs. One throat feeds each cylinder. The top carb feeds 1&2, the bottom carb feeds 3&4.

The fuel and air is pulled through the carburetor throats past reeds that open and close and into a bypass on the side of each cylinder. As the piston moves, it first scavenges the collected fuel and oil, then compresses it preparing it for fire. The same aft motion of the piston creates a vacuum behind it which pulls more fuel through the carburetors for the next charge.

The small hoses on the side of the cylinders' bypass covers run to the recirculation check valves, and have nothing directly to do with ignition.

See Bill Kelly's article here: http://www.maxrules.com/fixtheory2.html

 

[mikesea]

Re: 1981 115hp johnson, 3 outta 4 working

the lines you speak of are recirculation hoses that bring the residual fuel back to the intake,the fuel is delivered through the carb ,distributed by reed valves working on suction from the piston,Im thinking you got bad compression,water intrusion,or your carb is still plugges whithin a passage in its cast.

 

[borz170]

Re: 1981 115hp johnson, 3 outta 4 working

Check compression ASAP. Don't worry about anything else until you have compression results. These engines are simple, in essence. They take 3 things to run. 1. Fuel, 2. Spark, and 3. Compression. Everything else is just details. Important, but still details.

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Man ya'll are great!!!!!

Thanks again for all the help, this site is the best thing I've came across in a long time!

My number 3 is the one with the problem. I'll check the compression and let ya'll know!

Once I have the results, how do I go about ajusting this?

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Well bad news! My guy thats helping me just called and said that there is no compression cylinder 3... He said I'm going to have to have it board out. Does this have to be done on all heads or can it just be done on that one?

He told me that with him doing it it would end up costing about $1800 with parts and labor included. Is this right?

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

That's right if he does the job completely which means rebuilding the entire engine including the carburetors and giving you back a good running motor with some kind of limited warranty. The problem is that the market value of the whole motor is no where near that amount.

Before you go any further you should have him take the cylinder head and the bypass cover off so that you can see the damage for yourself. If you want to compare, check the cost of a rebuilt powerhead from one of iboats' rebuilders: http://www.boatmotors.com/motorparts/

You might also want to watch items like this one on Ebay; it's a carbureted 115 with about 20% more power than what you have: http://cgi.ebay.com/ebaymotors/1997...004QQitemZ140243897381QQrdZ1QQsspagenameZWDVW

 

[cdoliver]

Re: 1981 115hp johnson, 3 outta 4 working

I would look around on ebay before I paid that much for a rebuild. I found an entire powerhead with great compression on ebay for 250 bucks. Dropped it on my lower unit and its like a new motor. you can just bore that one cylinder if you want, but you might as well just do them all while you are in there. Depends on what the others look like. After you fix it, make sure you are running the motor at 5800 rpms wot and do a regular decarb. all the info you need is on this site.

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Well I got on Craigslist yesterday and found a 1982 115hp Johnson for $200.00. I went over there and checked the compression looked great!!! So I got it. Now I have two of everything. The lower unit and the prop looks great on the new one. The only problem with it is it fell off the stand and broke the housing on the outside of the powerhead. I may not be saying it right but its the exterior. The lower unit and the cover that goes over the whole thing it still perfect. The guy told me that this motor was great it just has to get warmed up first. I'm thinking that I will be able to just switch pieces between the two to build basically a new motor!

Anything that I should watch out for or replace while I'm doing this?

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

Be sure to get a factory service manual before you start. It will make switching that lower cover a whole lot easier because you have to pull the powerhead to do it. While you have it off, it is a perfect opportunity to rebuild the thermostats-Sierra kit # 18-3673.

You are going to need a powerhead gasket kit, it's the cheapest way to go.

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Luckily he gave me the manual when I bought this 1982 Johnson. I?ve been reading through it and it says anytime you have the opportunity to change the thermostat do it. So I?ll also need the gasket kit? Can I use the existing gasket with some liquid gasket on it? While I have this apart what else should I change?

 

[leatherneck514]

Re: 1981 115hp johnson, 3 outta 4 working

Well I got the power head that is running on 3 outta 4 stripped down. The only thing that has not come off yet is the fly wheel. I can't get it to losen up. I also can't figure out how to get it to seperate from the lower unit. I have taken 6 long bolts off the sides and then the 2 smaller ones toward the front along with the 2 self locking nuts. Is there anything else that has to come off first? The power head is able to lift up a little.

Thanks for the help!

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

The flywheel is torqued down well, so you need #8 Bolts to get the tool tight enough to free it once you have the bolt off. Are you using a harmonic balancer?

 

[ezeke]

Re: 1981 115hp johnson, 3 outta 4 working

Did you remove the two screws under the water hoses from inside the lower cowl? After that exhaust cover is removed, you can get the two nuts holding the adapter at the rear of the powerhead.

There is one screw and one nut that must come off each side at the front of the powerhead from below. They are just above the engine end of the steering fork/arm.

 

[mikesea]

Re: 1981 115hp johnson, 3 outta 4 working

You likely forgot the ones in the rear,think there r 2 7/16 head maybe 3.Also,as for the thermostats.In the Fl.Keys,we like to gut them.When you take them out,you will see a round collar type on the body,cut the 2 arms and the center rod,it will fall apart.If you run the engine in cold water,then you be better to change them.They are a bear of a job when on the motor and the location on bottom of block allows settlement of crud,thus failure.You need a flywheel puller not a jaw type,harmonic balancer remover using 3 bolts into the flywheel tappings.Be sure they are hardned theread EVENLY.Believe they are 5/16 fine thread