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johnson 115 idling issue

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flyer166

New member
Ok so here is what i got it is a johnson 115 model number j115tlarc that runs great above idle and on plane to 5500 rpm but if you shut it down to load or get the truck you have to prime it or fast idle it like a cold engine until you get it out on the water again. What i have done so far, i have replaced the themostats, both of them were gutted by previous owner, i have replaced power pack, removed soaked and rebuilt both carbs and replaced old cracked plastic bowls with new aluminum ones, i replaced all fuel lines and primer bulb, new vro, fresh plugs, and i have done the link and sync. I am about to pull my hair out and any help would be greatly appreciated. i dont know if the timing could be an issue i have checked it base timing should be 4 plus or minus 1 it is at about 2 right now. thanks
 
The model number of J115TLARC is not listed in any of my books. Double check it when you have time. The code is the word INTRODUCES where each letter represents a number from 1 to 0. If you transposed the last two digits and it is supposed to read "CR", that would indicate a 1984 model.

Your problem sounds like the fuel from the engine is being siphoned back into the tank after you shut it down. If using a portable tank, you may have a bad valve in the primer bulb. If a built in tank, see the following:

Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. Possibly someone has knocked out those inner components and converted it to a straight through fitting, OR the valve has stuck in the open position.

This could allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
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securedownload 2.jpgsecuredownload.jpgFirst off thanks Joe for the reply. I double checked the model number and it is correct I'm gonna try to include pics. I also pulled the pickup out of the tank and it does not have an anti siphon valve, I'm gonna try to put pictures of it on there, I don't know if I will have to have a whole new pickup or if there is an anti siphon valve that will score into the place of the barb for the fuel line. Thanks
 
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That would be a 1994 model.------These motors have a history of breaking the piston rings.----A compression test is the absolute first thing to do.
 
Thanks racerone for the response I guess I should have put that in my first post I have checked compression it was within 3 psi of 110 on all cylinders. I think Joe is on the right track with the anti siphon valve. Also what would be the best brand of primer bulb to use I was reading stories about cheap ones causing issues. Thanks
 
Instead of installing an anti-siphon valve in the tank fitting, just install a new bulb. You say it runs great above idle, to 5500 rpm. Does it idle? Can you troll with it?
 
Probably because they don't realize that everything is tied together somehow... or they just want us to guess.
 
Good point. Not trying to make fun of you, but have you read some of the posts on here?? "Enjun wunt sped up. Why?" And that's the whole post. :)
 
Ok just got in off the water, i had replaced the primer bulb and installed an anti siphon valve, no luck again the boat runs great going down the water but if you shut it off it is hard to restart and dosent idle well untill you run it up again i.e no trolling untill you get up on plane. Next question, should the carb flaps be closed all the way when you set the idle, and is the idle adjusted by timing?
 
So idle is controlled completely by timing and throttle follower should not touch cam until throttle is opened under acceleration.
 
something to try , while engine is running , pump primer bulb several good firm pumps. do you hear a difference in motor rpm ? if needle/seat are leaking you will flood motor and rpm will drop.
 
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