1976 Johnson 20hp poor idle

[AEROCOOK]

Re: 1976 Johnson 20hp poor idle

Are you sure you have a 1976 20hp? They show a 15, 25, and 35hp for that year.

Anyhoo, if it is similar to one of the above, there is a plastic seal called a "bearing" around the slow speed needle, way down in the hole. You can't see it, but it's in there (if it's a 1976) If it is worn it allows air to get in, upsetting the mixture. Note: this is not referring to the plastic friction retainer that you can see right where the needle goes in. The bearing is down in there somewhat and is part number 314166 and should be included with a carb kit.

I looked long and hard but I could not find the bearing that you mentioned. If I screw in the needle till lightly seated, the tip will protrude into the barrel of the carb, is this normal?
I was reuctant to use a screw to try to remove somthing that may not even be there for fear of damaging somthing.

 

[F_R]

Re: 1976 Johnson 20hp poor idle

If it has a bearing, and it probably does, it is way down deep in the hole, clear plastic. It fits around the reduced diameter of the needle. I have a long skinny screwdriver with a 1/8" blade that I gently poke into the bearing and carefully withdraw while rotating it. I also have a home made hook that works better. Never have personally tried the drywall screw method, but sounds good. One thing about it, once you embark on the removal process you are committed. They really should have called it a seal because if it is loose around the needle, air will be drawn in around the needle. If your carburetor looks anything at all like it's US cousins, it should take all the same parts and / or kit.

 

[AEROCOOK]

Re: 1976 Johnson 20hp poor idle

Thanks for the reply. I will take another look tonight to see if its in there. It's possible that someone had the the carb apart before and didnt re-install it. I just dont want to chew up the carb trying to fish somthing out that may not even be there. If the part is in fact missing, it could explain the 3 and a half turns out that I have to adjust the needle at just to get the motor to run at idle... extra fuel to compensate for the extra air??
BTW my local marina who incidentally recognizes my motor as a 1976 Johnson 20hp has confirmed that my carb should have this part in it.

 

[BF]

Re: 1976 Johnson 20hp poor idle

Hi,

Just a thought, but if the theory is that you have an air leak around the slow speed needle, couldn't you test that by temporarily putting some kind of sealant around the low speed need where it meets the outside of the carb (temporarily). ? If you put a glob of vaseline or slow cure caulk or a band or two of teflon tape, around the needle where it meets the carb, it should seal the air leak, but still allow you to turn the needle to adjust. If it adjusts properly and runs better, then you know what the problem is (and need to pull seal and clean the sealant stuff that you put on). If it doesn't change, then the seal isn't your problem... just clean up what you put on and look elsewhere.

I think it should work for diagnostic purposes... (?)

I'd also be suspicious of the spark/timing if you changed an ignition part right when the problem started... How about hooking on a timing light while it's idling? Then you could check the actual timing, and also see if the spark is intermittently failing... do one plug, then the other.

 

[Chachi420]

Re: 1976 Johnson 20hp poor idle

The first reference is from OMC's own archives.

For what it is worth BRP does not have a 1976 Johnson 115HP listed either. I suppose some could argue that ergo, they did not exist either.

Hey, I have one of those!

 

[AEROCOOK]

Re: 1976 Johnson 20hp poor idle

Well I was able to confirm that the bearing was not installed in the carb, I was able to shine a light down the hole and there was nothing down there. The hole seemed to get narrow with a shoulder about 3/4 of the way down, I assume the bearing seats on this shoulder is this correct? Then I went through the leftover parts from my carb kit and I found the part in question.
I put the part on the needle then wound the needle in till seated then back out 1 and a half turns. Is this the correct way to install the bearing?