1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

Joshua Buford

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ok any help someone can give me would be greatly appreciated. I have a 20hp johnson that i believe is a 1968 FD-20c. It was not running when i first got it. I have it running now and have even taken it out on the lake but it will not idle and i do not feel like I am getting to max RPMs on it. When I go to start it i have to go to full throttle or it wont start. when i start to throttle down it dies on me. If i throttle down really fast to go into gear and go right back to full throttle it works and runs. when i first got it the Nut that goes to the lean rough knob had been broken off so i got a new one and fixed that and recounted it to the valve needle (slow speed). The packing is also goon on the valve needle and i am hopping to fix that by the end of the week but i do not think thats way its not idling. If anyone knows what i need to do or can offer any help on this i would really appreciated it.
 

1946Zephyr

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

FD-20 comes up as a 1966 20hp. I would take a look at your ignition system. It sounds like it's dead on one cylinder, do to a bad coil or dirty points. If your coils look like the ones below, then it's time to replace them. Your low speed setting sound be 1 1/2 turns out from lightly seated.
 

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Joshua Buford

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

ok well after looking at some more stuff i think its a FD-22. see my vin number is not on there any more so idk how to find out what year it is im just going off of what it looks like compared to what i see online. but im pretty sure its a 1968. Its a rope start so i dont think i have a ignition system or is that under the flywheel and cover assembly?? ok thanks thats alot of help!! how many turns does the lower nut go?? the one to the lean rough knob?
 

ultra353

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

You should probably do a carb rebuild, including removing the welch plug and get your carb completly clean. If your asking about the low speed needle adjustment do like Zephyr said 1.5 turns out from seated position and go from there( unhook the knob on the faceplate to do your adjustments, once its set rehook the linkage). Do a spark check and a compression check first before you start putting money into it
 

Joshua Buford

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

Well iv already cleaned the carb. I just went out and set the low speed needle it was really really fare out. its starting right up now and idling like a champ. I think that might be the only thing that was wrong with it. How important is the valve packing? i just looked online were i got the parts from the first time and the shipping is $10 for a $2 part lol. or what would be something else i could use?
 

1946Zephyr

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

If you turn the packing nut in 1/4 turn, that should tighten it up enough to snug up the jet needle. You should be able to get packing, anywhere OMC parts are sold. I don't believe there is a high needle. Those just have a jet and the low speed adjustment stuff screws into that location. However, if there is by chance a needle, then those are 1/2 to 3/4 turn out. You may have an inspection plate on top of your flywheel, so you can get a visual of your coils, without removing the flywheel. If you get it running good by adjusting the needle, you're lucky However, you should take a look at your coils and make sure they look good.
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Joshua Buford

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

Yeah i have been using this to see what parts i needed to get for the carb. Part 35 is what i am needing now i have already got everything i was needed and replaced it. So part 43 does not do anything? I was missing that part when i got the motor i thought it should turn along with the top needle so its not in very snug. Should i tighten that nut? right now i think gas leaks out because it is not in very tight. Alright I will make sure to look at my coils. In less the man who sold me the motor changed them I would think they are getting pretty close to the end of there life just from the age of the motor. Thank you for helping me with this I really enjoy working on things like this but I still have a lot to learn, I am sure you can tell.
 

1946Zephyr

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

Yes, part 43 goes in tight. It serves as a plug for the high speed jet plus part of the low speed linkage. As far as part 35, that should have been in your carb kit, if you rebuilt the carb.
 

kfa4303

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Re: 1968 20hp johnson motor. WONT IDLE OR RUN STRONG PLEASE HELP!!!

Hi Joshua. I have a'66 FD-20c, just like your motor. Zephyr is correct, part #43, is the Hi sped needle for the carb and is fixed. They were adjustable on some earlier models. Both the Lo/Hi speed needles need nice fresh packing and perfectly clean/clear passages to work properly. Spraying carb cleaner in it without disassembling it, won't help and may hurt a bit. The good news is that rebuilding the carb is very easy and can be done in a couple hours with a $20 carb kit and a can of aerosol carb cleaner. I would also check/replace your ignition components too, just to be safe. That's also and easy DIY job. A new set of points and condensers (a.k.a. "a tune up kit" ) is only about $25 and only take about an hour to install. These are two of the simplest and most helpful forms of routine maintenance you can do on one of these old motors, but if you do it right they'll run trouble free for years to come. Here are some great links that can walk you through these jobs and others. You can get any/all parts you need right here at iboats and/or from most NAPA stores, although you may have to order them. Holler if you get stuck.


http://www.duckworksmagazine.com/07/columns/max/index1.htm

http://forums.iboats.com/showthread.php?t=167352

http://www.iboats.com/mall/partfind...=20&gd_search_14115=1968&**********=114837277

http://www.iboats.com/mall/partfind...2=1968&gd_search_4893=20&**********=114837277
 

Joshua Buford

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Hey everyone, it's been awhile since I've posted! I've recently board out my power head and fixed the other problems I was having that I mentioned earlier. I'm still unable to get the gear box to seal and I've replaced the seals twice. it also is slipping out of gear and sometimes freezing in reverse, not letting me shift into other gears. Most of the gear lube is leaking out from behind the propeller and I'm wanting to know if anyone has any ideas of what parts I should replace or if I can get the face of my gear box re-milled. Any advice would be greatly appreciated! Thank you!
 

restornator

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If you've taken the gearcase apart already, you should know whether or not your clutch dog is bad. I've done this before, but you may not have anchored the lower shift rod properly, either by forgetting the shift link screw or stripping it because it wasn't centered. Failing seals are a sign of an imbalanced propeller.
 
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