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1996 Johnson 112 SPL not running over 2000rpm

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youlost

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I'm having an issue where my Johnson outboard will sporadically decide it doesn't want to run about 2000 rpm. It usually happens while I'm on plane, she will drop rpms and stay at 2000rpm and 5 or 10 minutes later you will feel a couple of bumps in the motor and then it will rev back up and get on plane. Sometimes it does this right from the start when I put it in the water? I have had my carbs rebuilt twice and the issue is reocurring. Last trip to the boat shop they rebuilt/cleaned the carbs and replaced the power pack. I did replace all the fuel line, bulb, and filter but have not had a chance to run it yet. Drained all the fuel and didn't see anything out of the ordinary. I've had this issue for the past year and a half. I ran through 20 gallons (45 gallon tank) of gas this past weekend and on the way back in it started acting up again. It will slow down to 2k rpm then 5 or 10 minutes later you will feel a couple of bumps in the motor and then it will rev back up and get on plane. It's getting quite frustrating and I'm tired of doing the same thing to try and resolve it. Could this be the fuel pump going out sparadicaly? It also seems to have a weak idle and no adjustments to the carbs can seem to get it to idle above 600rpm. Idles fine when it is cold but idle is so week after you run it for 20 minutes or so that it's almost impossible to get it into reverse without it dying. Run's like a champ with no load on it on the ears.... Any help would be greatly appreciated. I hate bringing it to the shop because more times than not they will not be able to replicate the issue.
 
All motors run sound " great " on a hose.-----------I am not standing beside your motor, so do these tests.-----Report the results of a compression test.-----------Report the result of a proper spark check, as in will spark jump a gap of 7/16" on all 4 cylinders ??.----------When the motor falters does it help if the manual fuel pump is operated.------------To me it sounds like you are loosing spark on one or more cylinders, you can find out which one by running with a timing light and seeing which plug is not firing when motor falters.------Have you run the motor with the hood removed , it maybe spark is jumping from one of the plug leads to clamping bracket.
 
I had the compression check by the shop that replaced the power pack and rebuilt the carbs at the end of last year and he said all looked great. When the motor falters, it does not help if you pump the bulb, I checked spark plugs this weekend and they were all gapped properly. Now I havent run it yet since i replaced all the fuel line and the bulb. I did notice that I could not get the old bulb to get hard at all, even with the hose unplugged from the back of the motor. It doesn't do this all the time, only done it once in four trips so far this year. Like I said it had a new power pack and plugs put in the end of last year and ran great the 3 times I've taken it out. Everytime that this has happened, we have cleaned the carbs and it ran file for a while. I really don't think i should be cleaning carbs every 6 months. I always add stabil and the proper oil mixture with 100% gasoline everytime i fill it up.
 
If fuel is run out of carburetors each time the boat is taken out of the water then carburetors will stay clean.----------------Sounds to me like the valves in the primer bulb are defective.----Replace with a BRP factory new one.------Rebuilding carburetors ???----I wish I had $10.00 for every time I have read " cleaned carburetors and motor still runs the same "-------------So you have not checked for proper spark on this motor ????-Good spark is tested by a shop with an adjustable checker and it MUST be able to jump a gap of 7/16" or better !!
 
I had the carbeurators rebuilt by a local shop once and have cleaned them a few times. This usually fixes the problems for a little while. The shop checked for spark and replace a brand new Sierra brand power pack with what they said was a better brand. I did buy a new bulb at the West Marine store here. I told the guy behind the counter at a local boat shop that I couldn't get the bulb to get hard and he said you won't with a new bulb. Something about some new regulations that were put on them. I'm going to order a set of check valves for sure and take apart the carbs and put a new kit on each one. Thinking about buying a complete fuel pump assembly from here also and changing that out.
 
A primer bulb is nothing but a manual fuel pump.------Once the carburetors are full ( float valves close ) it should go hard.
 
he also sold me a straight through barb fitting to get rid of the anti-siphon one that was on it... What would keep the bulb from getting hard? I've replaced all the line from the tank to the motor. It will fill the clear fuel filter i added behind the bulb but bulb won't go hard even with the fuel line unplugged from the back of the outboard.
 
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Well i went ahead and put a new fuel pump on it and put a BRP bulb like suggested. I was running it on the muffs today and notices that if I trim it all the way down it, the idle gets a lot weaker and wants to die, as soon as I trim it up (just a little above horizontal) it runs fine. Sounds like a carb problem. I am going to take the carbs of and clean them and blow them out and put the new check valves on that I got in today. What would make it want to die if it was trimmed all the way down?
 
anyone? I'll be pulling the carbs off tomorrow, just wondering if there is something i should be looking for out of place...
 
Well I verified that there in fact was no water in the gas. Took the carbs off and brought them to my dad to look at and he helped me take them apart and said he has never seen a cleaner set of carbs before. I'm guessing something isn't setup properly on them? I looked at all the fuel hoses and replaced the check valves on the intake manifold while i have the carbs off.
 
I have the same problem! did you figure out what to do to fix it?
youlost said:
I'm having an issue where my Johnson outboard will sporadically decide it doesn't want to run about 2000 rpm. It usually happens while I'm on plane, she will drop rpms and stay at 2000rpm and 5 or 10 minutes later you will feel a couple of bumps in the motor and then it will rev back up and get on plane. Sometimes it does this right from the start when I put it in the water? I have had my carbs rebuilt twice and the issue is reocurring. Last trip to the boat shop they rebuilt/cleaned the carbs and replaced the power pack. I did replace all the fuel line, bulb, and filter but have not had a chance to run it yet. Drained all the fuel and didn't see anything out of the ordinary. I've had this issue for the past year and a half. I ran through 20 gallons (45 gallon tank) of gas this past weekend and on the way back in it started acting up again. It will slow down to 2k rpm then 5 or 10 minutes later you will feel a couple of bumps in the motor and then it will rev back up and get on plane. It's getting quite frustrating and I'm tired of doing the same thing to try and resolve it. Could this be the fuel pump going out sparadicaly? It also seems to have a weak idle and no adjustments to the carbs can seem to get it to idle above 600rpm. Idles fine when it is cold but idle is so week after you run it for 20 minutes or so that it's almost impossible to get it into reverse without it dying. Run's like a champ with no load on it on the ears.... Any help would be greatly appreciated. I hate bringing it to the shop because more times than not they will not be able to replicate the issue.
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