1990 johnson 115 0ver fueling issue

[brappley]

I have a 1990 johnson 115 hp, for the last two years it has been going through fuel excessivly, about 11 to 12 gallons per hour of WOT, is this normal ? ive had both carbs rebuilt, new VRO, plugs, ect, some times it runs great all day , but other days it just bogs down, wont idle, takes forever to come up on plane, ive talked to mechanics, taken it to the local marina, read all the posts, everyone says its a carb issue but dont / cant find any issues with them, the only thing i found was the lower carb float bowel is plastic and apears to be warped and i noticed the fuel passage runs through the carb into the bowel and up to the float needle, also pulled all 4 plugs and found the top 2 plugs where wet and the bottom where dry and grey colored, i checked compression and found 115 in 3 and 120 in the 4 th, 4 th being the top right side, any one have any ideas, if so please reply to my post.

 

[Silvertip]

Re: 1990 johnson 115 0ver fueling issue

The fuel burn rate (gallons/hour) of any engine will typically be in the neighborhood of 10% of its rated horsepower. So your 115 would burn 11.5 g/hr at WOT. Seems to me what you are experiencing is pretty close to typical. Compression is ok. Your understanding of how the carbs work is a bit incorrect. Fuel flow into the carb throught the inlet needle and seat which is controlled by the float. As the float bowl fills, the float rises until the level is reached where the needle and seat are pushed shut to shut off fuel flow into the carb. When running, the engine draws fuel through the idle, mid range or high speed passages based on how far open the throttle is. All plugs should be a light tan color. Wet with fuel says there is a spark problem. You need to read the plugs immediately after a 5 minute run at wot. Then kill the engine immediately (no idling). Wet plugs does not necessarily mean over fueling. It can mean "under burning" or "not burning". This engine IS running on all cylinders is it not????

 

[brappley]

Re: 1990 johnson 115 0ver fueling issue

Yes it is, i have heard that the fuel consumption is 10 %, thank you fo verifying, like i stated it runs ok one day then the next is just wont come up on plane or takes about a minute or two, i have to use the trim to raise the bow up to get the rpm higher , when it hits around 2400 rmp its like it gets a kick in the butt and goes, i guess you call it the power band ? Ive been told by the marina to install nauticus trim tabs, i watched a vidio on them and they seam to be what i think might do the trick as far as the planing issue.
Now back to the carb issue, i understand what you are saying about the path of fuel, but what i am saying is that the fuel comes into the carb from the inlet port on the float bowel, and there is a gasket between the bowel and the carb, the fuel seams to be passing through the gasket between the bowel and the carb body and filling the bowel with more fuel , i purchased a new float bowel , put my jets in the new one, new gasket, and i noticed a week later the bowel was warped just like the old on, now the part that makes me think this is the issue, if i run the motor with it completely level ( horizontal) it seams to run fine, but i use the boat on the river to troll up stream and tuck the motor down all the way and it seams to die due to flooding out, raise it up to level and it runs fine.
Now issue 3 , the wet top plugs, i saw that there are 4 coils, is there two sets of points, 1 set for 2 cylinders and 1 for the other 2 ? Might i have a bad or set going bad ? Thank you for your help, please let me know what you think.

 

[emdsapmgr]

Re: 1990 johnson 115 0ver fueling issue

The plastic float bowls on the OMC V6 crossflow engines in this time frame was a real problem. Probably the same bowls that you have on your V4 crossflow engine. Not a matter of if-but when the bowls would warp. The warpage occurs between the mating surface of the carb and the bowl. The problem runs from a simple fuel leak (high fuel consumption) into the cowling-to more serious problems. If the warpage is in a specific location of the bowl, the engine can suck additional air, causing the engine to run lean. The solution for the V6 problems was to replace the float bowls with the older (aluminum) style. If you reorder the original part number, you should get an aluminum bowl replacement. Best to replace that second bowl with an aluminum one like the top carb. Double check your float settings. If you have any excess fuel dripping out the front of either carb, it will collect at the bottom of the airbox. This excess fuel gets sucked back into the #4 cylinder through the airbox drain. When tucked all the way in, it can seem that the engine is flooding-exp at idle. Your engine has a solid state ignition system. No points. The rotation is sensed magnetically (no moving parts) in the center of the flywheel. It is possible that a component of that ignition system is breaking down once the engine heats up to normal operating temps. Could be any of these parts: stator, power pack or the timer base. Your compression is just fine.