johnson 115 dies after running

[richleroux]

hello all, I have a 1974 Johnson 115 and have been chasing a problem I cant figure out, first I should say that this motor has not been run in 10 years but it was due to the same problem I am encountering that it sat so long, so the engine starts fairly easily idles well and runs great for 5 to 15 mins after putting in the water then suddenly dies, it will restart a few more times but the problem returns at a faster rate until finally it will not restart at all till I let it sit for many hours. after having this problem the first time I took the boat home let it sit for a couple days. after some examination I found the electric choke solenoid was choking the motor all the time so I fixed that issue ran the engine at the house for almost an hour at varying speeds and no problem was sure I had fixed it. took it to the lake again today and after a little trouble getting it started it ran awesome for about 30 mins then the same reoccurring problem returned. I have been an auto and diesel tech for a lot of years but this is my first attempt at anything marine and I don't know much about them. im leaning toward the ignition module as ive seen many of them on vehicles do this same thing but it also seems like it could be a fuel problem as a few times after dying I turned the key and it wouldn't even crank like the cylinders were severly flooded, maybe more than one problem? I also am unsure of how the fuel delivery works is there an actual fuel pump? any help would be appreciated

 

[racerone]

Yes there is an actual fuel pump.-----Take the starter apart for inspection.----Run with a timing light and observe spark when motor falters.-----Changed the water pump impeller ?----Tested the overheat horn ?-------Checked for water in the fuel ?--------Checked pick up tube inside the fuel tank.

 

[Bosunsmate]

Check your spark can jump 7/16". When the ignition system warms up on these they can then show their faults, cold is often not when the issue appears

 

[racerone]

Is the " thermo electric " choke feature still hooked up ?-----Has the thermostat been checked ?

 

[richleroux]

brand new fuel tank so should have no issues there and fresh fuel, starter woks great except now and then pretty sure that's related to flooding or possibly timing, I have really not done much more than clean out the carbs out a little (without removing them as that looks like a pretty daunting task) and adjust the electric choke solenoid that is actuated by a toggle switch. was unaware these had a thermostat or where its located. noticed the fuel pump has 3 lines one pick up one delivery and a third im assuming is a vacuum?read on another thread that i could be getting a large shot of fuel through this vacuum line if I had a bad diaphragm? l also I have been unable to find anywhere to check the oil level anyone know how to do that?

 

[racerone]

There is no " oil level " on the engine.------You mix gas and oil at a 50 : 1 ratio.----The fuel pump is operated by a positive pressure pulse, not vacuum.----Yes a leaking diaphragm could flood one cylinder with too much fuel.-----Thermostat ( vernatherm ) is at the back below the exhaust cover.

 

[iggyw1]

If you have a brand new fuel tank, and fresh fuel, and did not know that you need to mix oil in with the gas, maybe your are real lucky that your motor died before it actually seized because of lack of oil. Try a 50 to 1 oil/gas ratio and see if it runs. If you ran it without any oil, you may want to go a little heavy on the oil now.

 

[richleroux]

well good to know its a 2 cycle engine I asked previous owner and he believed it to be a 4 cycle engine, I will for sure be adding oil to my fuel but I think im gonna throw a couple parts at it (a fuel pump and an ignition module) and change out the throttle assembly and wiring as I have an extra and my ignition switch and wiring are also suspects and the nearest lake to test in is 45 miles away so its rough to get it there just to figure out the problem isn't solved and apparently my problem wont present itself if I simply hook it up to some water in the yard.

 

[racerone]

Have to ask.----Was it run on straight gas , yes , no or do not know.-----Best report the results of a compression test !

 

[Tim Frank]

Check your spark can jump 7/16". When the ignition system warms up on these they can then show their faults, cold is often not when the issue appears

^^^^ +1

You can do that and a compression test without being at the lake.
The test above will verify the quality of the spark....when cold, if you do not get the 7/16" jump, you know the ignition system is not 100%.
If it is OK cold but fails when engine is warmed up, you can zero in from there.

On the fuel issue....how much running has it had without oil mixed in the gas?

 

[richleroux]

it was run on just gasoline since ive had it which was not very much run time since it keeps shutting down (which apparently a good thing since it had no oil lol) but im not sure if my father in law ran oil in it or not since he was the one that told me it was a four cycle but its been 10 years since he ran it so he may simply just not remember mixing fuel for it. I don't own a compression tester or a timing light anymore but I will attempt to borrow both from somewhere asap and give you guys feed back on that

 

[Bosunsmate]

you dont need a timing light for a spark test, just put two nails on a piece of wood 7/16 apart or better still buy a tester from a shop for a few $

 

[racerone]

It will run for about 9 -1/2 minutes with no oil in the gas.-----Then very serious / noisy things happen.

 

[Tim Frank]

It will run for about 9 -1/2 minutes with no oil in the gas.-----Then very serious / noisy things happen.

In the first post there appears to be almost an hour of run time if you add up the details.... I have no experience with the ACTUAL effect of this much non-lubricated running compared with the theory. Although I am always surprised at the resilience of these small OMCs.
Would the OP get any benefit from fogging the motor right away to try and get some lubrication reinstated to the innards?
Opinions?

 

[racerone]

Likely the damage is done !!---Adding oil / lube now is futile , waste of time.------It is so easy to remove the bypass covers to inspect the pistons / rings.------So easy that many owners can not believe that you can do this simple inspection !

 

[richleroux]

ok so what exactly are bypass covers? and will i need parts (gaskets and such) to reassemble it?

 

[racerone]

There are 4 covers .---6 wee 1/4" bolts per cover.-------One above the other on each side of the block.----2 on each side of the block.------Might need 4 gaskets at $2.00 each.-----If it is worth re-installing those covers.

 

[richleroux]

ok so after talking to father in law this engine has never been run with 2 cycle oil!! and has always had this runability problem. he insists it is a 4 cycle engine though im fairly certain its a 2 cycle so is there a way to be positive its a 2 cycle? I cant find any supporting literature that will tell me for sure. I added oil to the fuel yesterday and also pulled the plugs and put just a little oil in each cylinder and the turned the motor over and reinstalled the plugs to lube it up. still couldn't locate a compression tester to do a compression test but id does still have compression. started it up and it smoked like hell but ran ok till it began to overheat (my fault i think tried putting it a tote of water instead of running the hose to it so it wasn't so loud). gonna give it another try today if weather permits with the hose hooked to it as usual. does the engine have to be in gear for the cooling system to work? there is no water I can see running out of the engine anywhere which doesn't seem correct if im supposed to be getting flow through the cooling system

 

[spybot]

The motor doesn't need to be in gear for it to pump water.
But I think either the motor is toast or you are a very very lucky guy with a bullet proof motor.
Did you have a look inside the by--pass covers ?
How long did you run it till it over heated ?
Did the over heat buzzer/alarm go off? In my opinion if it did that's normally too late as the damage has been done.
I hope you get it running but I think the more you do the worse your making it.
As said go through the trouble shooting one step at a time.

 

[richleroux]

yeah im thinking your right only took maybe 5 mins of running till the buzzer was screaming at me again, I removed one of the two hoses coming off the back of the heads which im assuming are coolant hoses and im getting nothing but steam and some exhaust out of them and no water flow coming out of anywhere while running, think its beyond me and cant afford to take it 100 miles to someone who knows what they are doing much less pay them to fix it think im just gonna start looking for a replacement motor though not sure how I will afford that either thanks for the help guys