Home › Forum › Ask A Member › 1974 Evinrude 9.9 won’t idle at low RPMs, need help
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fleetwin.
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April 24, 2016 at 1:42 pm #4121
So I will start off with the warning that I’m not mechanically inclined. This motor has been my effort to learn how to do this stuff. I have learned a ton off forums like these and accomplished a decent amount on my own, but have come across a problem I need help with. This has been an ongoing problem, and the most recent development is that I was referred to this forun for advice.
I picked up a 1974 Evinrude 9.9 at the end of last summer in decent shape, ran rough. The throttle has to be up for it to run. As soon as I try to bring the RPMs down, it sputters out and dies. I find that in order to get it to start I really have to rev it up. Also, it runs best at 1/4 choke. I played with the idle needle adjustment first, but it didn’t fix the problem. I pulled the spark plugs… They looked ok to the untrained eye. One was a little black, but i cleaned them up pretty well i think. After reading FAQ’s and other established threads, all signs pointed to a dirty carb. So I pulled it apart today, but it was spotless. Not a spot of carbon in it (I should point out that I got lucky and this motor is in very good condition… Everything is very clean, there is no corrosion or other sign of wear. There is no seeping oil).
One thing I did notice when the carb was off, was that the float was slightly off of parallel with the carburator body. I fixed that (the float was updated by the previous owner, apparently. Black plastic, clean no cracks). There was no corrosion or pitting in the float bowl (it’s the metal fuel bowl). I put everything back together (including backing out the needle 3/4 from lightly seated) then reassembled the motor. There was a definite difference in running it and adjusting the idle, but it still has the same problem. When I try to throttle down and drop the RPMs, it sputters out and dies. It also makes sounds like it’s backfiring (i don’t know if that is what people are referring to as "sneezing"?). However, at higher RPM, it does run smoother and longer than it did before. I can scale the choke back a bit more as I adjust the idle, but I can never get it to the point where it runs without choke. I replaced the gaskets on the carb, so I am hoping I have ruled out the possibilty of air getting drawn into the carb from the seals.
I’m sorry this is long winded and probably confusing, but I have a video of how it runs after I put the carb back on today
Can anyone point me in the right direction on this? I apologize if this seems easy to the seasoned vets but I’m trying to figure out how it all works.
April 24, 2016 at 1:47 pm #35373There is a real good chance the top oil seal is worn. I had one with the same problem and replacing the seal fixed it. You need to pull the magneto off the get to the seal.
April 24, 2016 at 3:01 pm #35379quote mercuryman:There is a real good chance the top oil seal is worn. I had one with the same problem and replacing the seal fixed it. You need to pull the magneto off the get to the seal.So, is there potentially air seeping in at that seal? Is that what the problem is? Because i have to run it at no less than 1/4 choke, so my thought process was that it needs more fuel because it is getting too much air.
Sorry if this seems simple, I’m just trying to learn as much as I can.
April 24, 2016 at 3:15 pm #35380The other part of that statement on the seal is that you can normally see a black "drool" coming down and around the powerhead from up under the flywheel. If you see that then check it.
You mentioned zero about cleaning out any passages in the carburetor….only a visual. Please elaborate.April 24, 2016 at 3:50 pm #35386A compression test will give you a good idea of what condition the motor is in. Look for at least 80 Psi,after 5 pulls of the starter cord. Pull that cord like you mean it, both plugs out.
The carb low speed needle should be set at 1 1/4 turns out counter clockwise, after turning it in clockwise all the way to lightly seated ,not forced closed all the way,that’s your starting point.
Do you have fresh gas at the proper 50:1 ratio? Did you start with a clean tank and hose,no water in the tank ?
Looks like it’s smoking a bit , should be able to run without the choke .
Feel the top of the motor,the flat spot right above the cylinder head. Is it warm? It should be quite warm ,if not your thermostat is stuck open or missing.
Our experts here will chime in with a lot more tips,and welcome to the forums."Some people want to know how a watch works, others just want to know what time it is"
Robbie RobertsonApril 24, 2016 at 3:54 pm #35388quote Pappy:The other part of that statement on the seal is that you can normally see a black "drool" coming down and around the powerhead from up under the flywheel. If you see that then check it.
You mentioned zero about cleaning out any passages in the carburetor….only a visual. Please elaborate.I don’t see any drool, the motor is pretty clean.
I snaked tiny wires through the passages when I had it apart yesterday. I sprayed it with carb cleaner as well, but it was near perfect condition when I pulled it off…. The gaskets were almost brand new, there were no obstructions in any jets and the float had even been updated to the black plastic (as opposed to the original varnished cork). This was when I noticed the float was almost a millimetre off parallel. Fixing this made a definite change, but didn’t fix the problem.
It was suggested in another forum that I would need to pull the welch plug and get into the low speed circuit again? Apparently it can take a couple tries?
I also tested the fuel line, it has pretty strong flow coming out of it.
April 24, 2016 at 4:06 pm #35389Start with the basics then. What number of turns are you setting the low speed needle at?
April 24, 2016 at 4:11 pm #35390quote pugetsoundboater:A compression test will give you a good idea of what condition the motor is in. Look for at least 80 Psi,after 5 pulls of the starter cord. Pull that cord like you mean it, both plugs out.
The carb low speed needle should be set at 1 1/4 turns out counter clockwise, after turning it in clockwise all the way to lightly seated ,not forced closed all the way,that’s your starting point.
Do you have fresh gas at the proper 50:1 ratio? Did you start with a clean tank and hose,no water in the tank ?
Looks like it’s smoking a bit , should be able to run without the choke .
Feel the top of the motor,the flat spot right above the cylinder head. Is it warm? It should be quite warm ,if not your thermostat is stuck open or missing.
Our experts here will chime in with a lot more tips,and welcome to the forums.The fuel is a couple months old, 91 octane. I also have an old metal gas can without a vent so i crack the lid (it is definitely the original gas tank, its super old). I have recently read that 87 Octane is recommended for my motor, so my plan for next weekend was to get a new, cleaner gas tank with a proper vent and some fresh 87 Octane. Would it be a good idea to replace the spark plugs, since they took a good cleaning when i took them off yesterday? I had read that you had to use a slightly hotter spark plug with this motor for better firing at lower rpm/idling (the original spark plug is apparently out of production). The part number that has been given is NGK BR6HS, can anyone confirm this? I didn’t think to check on this when I had it apart yesterday and see if I had the right spark plugs. But it starts up pretty quickly so i figured it wasn’t the spark plugs.
Every time i push the choke in all the way, it sputters out and dies (makes a backfiring noise). I tried to counter this with the idle adjustment, and i got it to run pretty smooth at 1/4 choke (before i played with this, it ran smoothest at half choke), but it still peters out when i try to take the choke all the way off.
I did feel the top of the motor. It was warm, but not uncomfortable to the touch. I had read that this was a sign the water pump was working because there is no telltale? Also, as the motor warmed up, more water came out the exhaust hole on the back, which I had also read was a good thing.
April 24, 2016 at 4:16 pm #35392quote Pappy:Start with the basics then. What number of turns are you setting the low speed needle at?Before I pulled the carb out, i started at 1 1/2 from lightly seated. After i put it back in, i started at 3/4 (as per instructions with the carb kit). I found that the motor worked best around the 3rd full turn from lightly seated. If I continued turning, it would start to die out quicker again. After I put the carb back on, it started way stronger at 3/4 turn, but I suspect thats also due to the float adjustment
Edited out spelling errors
April 24, 2016 at 4:26 pm #35393My 1st guess is that the high speed orifice (jet) is partially clogged. That would account for the excessive choking need. 2nd guess (well actually 1st) is have you heard yet that those motors were notorious for fouling spark plugs? Are you sure it is running on both cylinders? Try new plugs, I don’t care if they were just put in recently. I’ve seen brand new motors that wouldn’t run one weekend without fouling plugs. Bad.
3rd guess is major air leak. But let’s not go there yet.
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