'84 Johnson 115 V4 lean sneeze?

fmjnax

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Just picked up the boat and rebuilt the lower unit. Engine is an '84 Johnson 115. Took it out for its maiden run yesterday. It runs perfectly fine at WOT. At idle, it seems to backfire. Compression is perfect on all 4 cylinders and the plugs looks good. I think it's running lean. I read through my manual but I cannot figure out how to adjust the idle jet (rather, I can't find the idle jets!). There are 2 carbs; each one a double-barrel. There is a rod just before the butterfly from top to bottom. There is an orifice on the top inside of each throat (but they don't turn). Any ideas where to adjust? Or is this a link-and-sync only model?
 

racerone

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There are no adjustments.for mixture !------Check that all throttle plates are closed at idle.----Possibly throttle plates are opening too soon.------If sneeze persists then visit your friendly shop for advice on changing idle jets.
 

fmjnax

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Still trying to track down the problem. Here's what I know:

- Compression is good.
- Spark is good and all 4 plugs look to be firing the cylinders fine.
- I have flushed the tank and lines and replaced with fresh gas, pre-mixed properly.
- The carbs have been cleaned and rebuilt. I replaced all 4 of the #34 orifice plugs (boy are those things expensive!)
- The butterflies are fully closed and seated at idle.
- The butterflies are perfectly horizontal at WOT.
- The carbs are in sync and open/close at the same time.
- The plastic roller cam is in perfect condition.
- I can use the "warm up" lever and at a very fast idle the problem is gone. However, the boat won't idle or troll at low RPM's.
- At WOT, I don't believe there is any backfire, but I guess it's possible that it's there and I just don't hear/see/feel it. Seems to run perfectly fine at speed.

I don't know exactly what RPM's the engine is running at as the tachometer doesn't seem to be functioning properly (still working on it). I'm going to take a look at the fuel filter this evening. What else should I be looking at?
 

fmjnax

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Jul 21, 2011
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Still trying to track down the problem. Here's what I know:

- Compression is good.
- Spark is good and all 4 plugs look to be firing the cylinders fine.
- I have flushed the tank and lines and replaced with fresh gas, pre-mixed properly.
- The carbs have been cleaned and rebuilt. I replaced all 4 of the #34 orifice plugs (boy are those things expensive!)
- The butterflies are fully closed and seated at idle.
- The butterflies are perfectly horizontal at WOT.
- The carbs are in sync and open/close at the same time.
- The plastic roller cam is in perfect condition.
- I can use the "warm up" lever and at a very fast idle the problem is gone. However, the boat won't idle or troll at low RPM's.
- At WOT, I don't believe there is any backfire, but I guess it's possible that it's there and I just don't hear/see/feel it. Seems to run perfectly fine at speed.

I don't know exactly what RPM's the engine is running at as the tachometer doesn't seem to be functioning properly (still working on it). I'm going to take a look at the fuel filter this evening. What else should I be looking at?
 

emdsapmgr

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Dec 9, 2005
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Likely the carbs need to be cleaned. A "lean sneeze" at idle every rpm or two is an indication that the engine is indeed running lean at idle. It's a carb issue, not spark. The idle passages in the carb get restricted over time with dried fuel gelatin. From it sitting for a long period of time with fuel in the carbs. The light parts of the fuel evaporate, leaving the gelatin which will restrict the flow of fuel at idle. Only way to resolve it is to tear the carbs completely down and use an aerosol cleaner, like a Gumout product to clean the passages. If you get the carbs just off idle, it usually clears up, as the mid and high speed jets provide enough fuel to keep it from sneezing. You can't resolve the problem by just running some fuel cleaner thru the fuel tank.
 

fmjnax

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That's what I thought emdsapmgr, which is why I pulled the carbs, cleaned them, and replaced all 4 of the low speed orifice plugs. Problem still exists.
 

fmjnax

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That's what I thought emdsapmgr, which is why I pulled the carbs, cleaned them, and replaced all 4 of the low speed orifice plugs. Problem still exists.
 

emdsapmgr

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So, it's still running lean at idle. How did you clean the upper carb passages? I use Gumout aerosol. Remove the jets. Spray one passage on one throat of one carb. Note the spray coming out the other end of the carb. Then spray the same passage on carb #2. Note the spray volume coming out the other end of the carb. Both spray patterns/volume should be identical. Go thru the whole carb, comparing your gumout spray pattern between the same passages on both carbs. If one does not spray identical the other, it's restricted and is the problem. (needs extra cleaning.)
 

pn

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ditto on emds, make sure everything snug on your carbs too.
 

fmjnax

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When I cleaned the carbs, I removed every orifice plug and core plug (except for the ones that look like lead shot). I first blew them out with compressed air, then used PB Blaster. Another shot of compressed air and then a good soaking in carb cleaner. I final shot of compressed air and then an air dry. Once dry, everything was re-assembled. I ensured that the float was correct and that the needle was in perfect condition. I did the blow-by test to make sure. New core plugs, new orifice plugs, and new gaskets were used. Everything was torqued properly.
 

emdsapmgr

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Did you perform the normal sync and link procedure? Is the link arm connected between the timer base and the spark advance lever? Does the timer base move smoothly as the spark advance lever moves?
 

pn

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you might try putting a small bit of epoxy over those bb plugs/shot plugs. possibly loose clamp, possibly a reed.
 

emdsapmgr

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Are both sets of carb butterflys completely closed at idle? (they can get mis-adjusted)
 

fmjnax

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Here's the latest:

- Completely disassembled the fuel filter/pump. Perfectly fine there. No gunk and the diaphragms were good
- Checked fuel lines (again). All good
- Checked butterflies. All 4 a closed completely and move at the same time
- Fast idle moves the arm smoothly and fully returns
- Reeds are all in-tact and look good

Since I was checking the reeds, I have decided to clean the carbs again, just in case (will be doing this tonight). I'll also try some epoxy on the lead shot.

I am going to do a decarb on the motor this weekend, and will then install new spark plugs.

On another forum I posted a picture of my current spark plugs and was told it looks like the motor is running rich, and not lean. I've attached the same picture. Do note that the plug on the left and the second from the right looked just like #2 and #4, I had just rubbed off the deposits. Also, this is after a lot of idle on the muffs while diagnosing.
20140712_171617_zps1333f117.jpg
 

jakedaawg

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Spark plug reads dont tell much in this situation. If you still have a lean cough after redoing carbs I suggest looking for another air leak.

Replace a section of fuel hose with clear to look for air bubbles.

While checking this spray some carb cleaner around the intake manifold seal, the block halves, and up under the fly wheel. You can also use propane (an unlit torch of course). If you get an rpm change that is where your problem is.
 

fmjnax

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LOL! I was surprised on the no-error as well.

Good idea to try to find an air leak. I will certainly do that. On the other forum post, the guy also mentioned that perhaps the timing is off. Is that a possibility as well?
 

emdsapmgr

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These crossflows run rich at idle, so if the plugs look wet-that's normal. At WOT is where they are light tan and dry.
 

fmjnax

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Yeah, I didnt think they looked bad.

I re-cleaned the carbs tonight, using an entire can of carb cleaner. I have a small shimmer of hope when I test it on Saturday. I pulled the low speed orifice plugs and the 1 that I obviously didnt replace (guess I only bought 3) looked to be gummed up. I could see through it but not as much as the 3 new ones. I ran some wire through it and cleaned it out so that it looked the same. Im hoping this stupid oversight was the problem. I will update again on Saturday.
 
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