1966 johnson jw-21 3hp.....baffled on this one!

nwcove · May 3, 2012

this little motor is being a pain!! went to look, comp was 95 in each hole,good strong spark, but would only run with fuel sprayed into the carb. i thought no big deal, needs a good cleaning and a kit. well did that..soaked it for a week, cleaned all orifices with a wire and blew them out. checked the carb for cracks. put it back together and still its a no go. took it apart again, did a reclean and used a welch plug left over from another kit, still nothing unless i spray fuel into the carb, then it starts very easy and dies when the fuel is used up. it is filling the bowl with fuel, the motor just isnt getting it! any thoughts ? ( the carb is now spotless, and ive done many without an issue like this)

Daviet · May 3, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

How is the fuel flow out of the tank to the carb, there is a filter screen on top of the shut off valve.
You say it runs till it empties the carb bowel, is the needle/seat passing fuel, is the float set properly?

tx1961whaler · May 3, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

Check the high speed nozzle and gasket and make sure they are in place and the nozzle is not cracked.

boobie · May 3, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

If the carb bowl has a plug in it, pull it out, turn on the fuel and make sure fuel keeps running out of it.

nwcove · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

Daviet said:
How is the fuel flow out of the tank to the carb, there is a filter screen on top of the shut off valve.
You say it runs till it empties the carb bowel, is the needle/seat passing fuel, is the float set properly?

fuel flow from tank to carb is perfect, float is working and set level. it wont run at all unless i spray premix into the throat of the carb, then it only uses what was sprayed into it, doesnt seem to be sucking fuel from the bowl.

boobie · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

Not to insult you, but I think you're missing something in the carb. Or else the mtr just plain won't suck. How are the reeds ? Even tho' the compression is good, could the bottom rings on the pistons be stuck ??

nwcove · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

took it apart again....all parts are accounted for except possibly one ( unless its threaded in) #39 orifice plug, i can remove # 41 plug screw and it drains the float bowl in a hurry. i ran it for a half hour today by force feeding fuel directly into the carb throat and it ran well and sounded good . reeds are the next thing to look at i guess.

http://www.marineengine.com/parts/vintage-evinrude-johnson/381410/catalog.html

page 5

Daviet · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

If it will run by squirtng fuel into the carb, you have a carb problem.
When you cleaned the carb did you remove the core plug on top of the carb (#7) and clean the tiny passages in there?
#39 is the high speed jet, if you can't remove it to clean it you can use a bread tie without the plastic cover, insert it through the bowel drain and see if you can clean the jet.

nwcove · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

core plug removed twice and replaced and sealed twice, and the passages cleaned twice, didnt run a wire through the bowl drain though, but will try that. ( air blows through it ,and fuel runs out no problem).

Daviet · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

All the passages in #10 clear?

nwcove · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

#10 is clean as a whistle.

boobie · May 4, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

# 39 has to be clean for the carb to work.

nwcove · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

pulled the carb apart again, had a close look at things, part #36 from the kit ( thick rubber washer) was about 1.5mm thinner than the original, put the old rubber washer back in.....three pulls and it lives!!! idles slow, revs good, starts easy. not sure if i got a part that missed qc , or if its an issue with the kit?

tx1961whaler · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

It's an issue with some kits. That's why I mentioned it earlier. If the nozzle is cracked, or the washer is out of place it will not run.

smeltjr · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

nw - what kit did you use? aftermarket or oem? and tx what kits have you noticed this in? mine's a head gasket. nw, did your cam have an index?

nwcove · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

smeltjr, the kit was not oem,and it was the carb kit. kudos to tx! i didnt change anything with the sync on the motor, but if you did the carb cleaning, make sure you pull the aluminum plug at the top and clean the carb right. ( and dont take it for granted that new parts are right! never had a prob like that before, but it was an issue)

tx1961whaler · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

I've noticed with some Sierra kits that the "fat grommet" is sometimes not the same as the original. You can tell that the carb bowl does not mash down the same when reassembling the bowl to the carb body. I just re-use the original if they don't match up.

1946Zephyr · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

That's okay, if the original doesn't crumble like stale bread, when you pull it apat.

Part-time · May 5, 2012

Re: 1966 johnson jw-21 3hp.....baffled on this one!

It sounds to me that the air is getting in somewhere other that the carb... could be reeds or also could be crank seals.
I had a 3hp Sears outboard that would not run unless I force fed it through the carb like you described and crank seals fixed it after 3 or 4 good carb cleanings did nothing for it.
I also have a 250cc polaris 2 stroke quad doing the same thing right now and a 15hp nissan that needs a good gulp of fuel directly into the carb to start and only runs at 1/2 trottle or more and I suspect crank seals in both of them as well.

1966 johnson jw-21 3hp.....baffled on this one!

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