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115 Johnson V4 - 1984 wont accellerate

S

Sturos

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Can anyone help, I have a 1984 V4 115 Johnson. up till the weekend it was running fine. took the boat out and fired up fine. idled away from the boat ramp fine till I tried to increase the throttle past about 2000 rpm. it missed and just could not increase RPM at all. when I backed off it ran rough for a bit then settled down. take it out of the water and fire it up and it revs out to 4500 fine. can anybody help?
 
Revving it out of the water risks major damage to motor and means very little and proves nothing, it will do that running on 2 cylinders.------------Do a compression test first.------Then check to see if you have spark on all 4 cylinders that will jump a gap of 7/16" with a snap you can hear.---------Could also be as simple as water in the fuel.----------Trouble shooting is the path forward.
 
Thanks Racerone- Comp test Ok but couple of PSI down on 1 cylinder-Ive washed out the fuel tank with Metho and put fresh fuel in Im using premix- How do I go about checking the spark? Sorry can pull apart the mechanicals OK but very poor with electricals. If the spark is Ok does that mean the coils should be alright-If thats Ok Ive cleaned out the tank I presume the next step is to check the carburetors, any simple way to quickly check them of run a fuel additive through, or do I need to pull them off and strip them down? your help is greatly appreciated, I have to make this old motor last for a while yet.
 
You need to establish a 7/16" gap to properly test for spark. Laying a plug on the block is not good enuff.-------Perhaps have a shop check this for you , as it is a must do check.-----------If all that is good then look for a fuel issue. Could be a ruptured diaphragm in the fuel pump.Blockage in a carburetor.Water in the fuel.----------Best not to run the motor untill you determine what is wrong.
 
Thanks again for the help. Im trying to learn about the motor and am quite happy to have a go at some of the more basic things. howver this looks like ot could be a lot more involved than I had hoped so Ill heed the advice and get it checked.
 
Had a cousing bring his 84 Johnson V-4 over for a check.----Took about 5 to 10 minutes to check condition of motor.---After the rebuild he said " does that ever run smooth now " just loves the motor.-----------Mid 1980's motors are great , simple machines.
 
Did you finnaly find what was the problem. I Have the same proble with my Johnson 1984 115HP And I dont really know From where to start ...
I just buy it last week and the only thing iv done is changing the plug !
Sturos said:
Thanks Racerone- Comp test Ok but couple of PSI down on 1 cylinder-Ive washed out the fuel tank with Metho and put fresh fuel in Im using premix- How do I go about checking the spark? Sorry can pull apart the mechanicals OK but very poor with electricals. If the spark is Ok does that mean the coils should be alright-If thats Ok Ive cleaned out the tank I presume the next step is to check the carburetors, any simple way to quickly check them of run a fuel additive through, or do I need to pull them off and strip them down? your help is greatly appreciated, I have to make this old motor last for a while yet.
Click to expand...
 
You can stick a well insulated handled screwdriver gently into one spark plug boot at a time. Have someone crank the engine while you hold the screwdriver shank the 7/16" (the best you can guess) off of the engine block. May want to mist some lube in the cylinders first.

I had one cylinder of my '75, 115 Johnny not firing. Ran fine on the hose, although it did sound a little different, but not like it was missing, but in the water had to keep the fast idle lever up. Noticed that the dead cylinder had no temp on the plug like the others, by feel. Squirted some fuel/oil mix and the cylinder hit. I overhauled the carbs and found nothing by eye and all parts and setting looked good. Shot carb cleaner thru all of the carb passages and found no blockages. However, when I put it all back together, it ran like new.
 
I had the same trouble with my 1980 115. Idled great, nothing past 3000 rpm. Used a timing light to check for power to the plugs after finding that one was wet with fuel. Only 3 cylinders were firing. Turned out to be a bad coil.
 
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