johnson 20hp 1967 HELP PLEASE,

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boaty paul

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i have just aqquired a johnson 20hp 1967, that has been sitting in the back of a garage for 10yrs, it pulls over well has got good sparks on both cylinders, but when i try to start it all it does is trys to start and konks out straight away, and when trying to start it it backfires on me, i have changed the leads around but still does it , could it be carb thanx
 
Replace the plugs, old plugs will spark but can fail under compression
Use fresh fuel with the correct two stroke oil, if it has a separate oil reservoir check there is no blockage
Clean the points and set the gap, change the air filter
As long as there are no broken wires etc it should start
 
Agree with Bouba, but I'd add that every area where fuel has been (tank, pipes and carburetor) need dismantling and thorough cleaning. Why? As time goes by the petrol and oil mix evaporate leaving a gum-like residue. Not a huge job.
 
And I just remembered in the bath that Johnsons were fitted with something called the 'Fitch' or 'Fidch' starter or injection. These were notorious but I think it might have been in the 80's
Old 2 strokes are easy to work on there is not much to them
 
Ok remembered one more thing before I go for breakfast, if it has a magneto (sorry can't spell it) check that the woodruff key has not sheared off
 
boaty paul said:
i have just aqquired a johnson 20hp 1967, that has been sitting in the back of a garage for 10yrs, it pulls over well has got good sparks on both cylinders, but when i try to start it all it does is trys to start and konks out straight away, and when trying to start it it backfires on me, i have changed the leads around but still does it , could it be carb thanx
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When you say has good sparks do you mean just observed on the plugs or direct from the leads. You should be able to pull a 1/4" long spark from the leads. If not on a Johnson of that age suspect the coils.

If you pull the flywheel use the correct type of puller ( harmonic balancer puller) not from the rim with an ordinary gear puller . When refitting be sure to tighten the retaining nut to the correct torque ( 40-45 lbsft)

A good idea to check the compression. At 60 psi it should run but better if 80 or more. The cylinders should be within 10% of each other.

Change the spark plugs if in any doubt about them. Currently recommended plugs are Champion J4C gapped at 0.03"

However I suspect as you do that the carb needs cleaning. Use fresh fuel ( correct fuel mix by the way is 50:1)


Workshop manual which covers the model at http://boatinfo.no/lib/evinrude/manuals/1956-1970johnsonevinrude.html

I would also check the gear lube and renew the water pump impeller before using it .... you don't want bits of broken impeller blocking the waterways
 
hi there, thanx for all your help on the engine, ive had the carb of and it was as clean as the day it was made , jets all fine and clear , all looked good in there, now to the fuel pump, can you tell me how i would be able to test that please , thanx boaty.
 
boaty paul said:
hi there, thanx for all your help on the engine, ive had the carb of and it was as clean as the day it was made , jets all fine and clear , all looked good in there, now to the fuel pump, can you tell me how i would be able to test that please , thanx boaty.
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If you disconnect the fuel delivery hose and crank the engine you should see spurts of fuel if the pump is OK
In anycase once you have filled the carb bowl with the primer bulb the engine should start and run for short while even if the pump is not pumping and you should be able to keep it running by repeatedly squeezing the bulb
 
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hi there, thanx for all your help on the engine, ive had the carb of and it was as clean as the day it was made , jets all fine and clear , all looked good in there, now to the fuel pump, can you tell me how i would be able to test that please , thanx boaty.
 
hi, im new at all this where do i find the fuel delivery hose, and yes when i prime it , it does work for about 10/15 seconds at most, but not tried to keep priming it yet
 
This may or may not be relevant but old two stroke exhausts coke up really badly and will stop the thing working. Now I know outboards have very short exhausts but it's worth checking
 
hi there, as i say im newish to all this , how do i do that , i had it running and revved it up last night , but only for 10 seconds before it stopped again on it own accord , how do it check the fuel pump, as it may be fuel starvation, thanx
 
boaty paul said:
hi, im new at all this where do i find the fuel delivery hose, and yes when i prime it , it does work for about 10/15 seconds at most, but not tried to keep priming it yet
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boaty paul said:
hi there, as i say im newish to all this , how do i do that , i had it running and revved it up last night , but only for 10 seconds before it stopped again on it own accord , how do it check the fuel pump, as it may be fuel starvation, thanx
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By fuel delivery hose I mean the hose between the pump and the carb

i'd expect it to run for longer 10-15 secs but if the fuel pump is defective or there is air being drawn into the fuel line you should be able to keep it running by regular squeezing of the priming bulb.

Bouba said:
This may or may not be relevant but old two stroke exhausts coke up really badly and will stop the thing working. Now I know outboards have very short exhausts but it's worth checking
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Which parts are you suggesting might be coked up. Can you identify them on the parts diagrams http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1967&hp=20&model=FD21
 
VicS said:
By fuel delivery hose I mean the hose between the pump and the carb

i'd expect it to run for longer 10-15 secs but if the fuel pump is defective or there is air being drawn into the fuel line you should be able to keep it running by regular squeezing of the priming bulb.



Which parts are you suggesting might be coked up. Can you identify them on the parts diagrams http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1967&hp=20&model=FD21
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In 'the lower unit group' number four is the exhaust housing. If there is an exhaust inside this housing I wouldn't know without getting some spanners to it. But starting then dying is a symptom of a coked up exhaust (or baffle if it has one). Old two strokes don't combust cleanly hense the smoke and the reason they has been outlawed
 
hi vics, when i connect my fuel line up to the engine , my connection leaks , is it spozed to or could that be why it wont start, i have checked compression in both cylinders and they are 80 and 85 , i have about a 10mm spark from the bear lead end , and good spark at plug, fuel getting to the carb,, and still wont stay running ???? fresh fuel 50.1 thanx paul.
 
boaty paul said:
hi vics, when i connect my fuel line up to the engine , my connection leaks , is it spozed to or could that be why it wont start, i have checked compression in both cylinders and they are 80 and 85 , i have about a 10mm spark from the bear lead end , and good spark at plug, fuel getting to the carb,, and still wont stay running ???? fresh fuel 50.1 thanx paul.
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If the fuel line connection is leaking it can let air in when running. That will starve the engine of fuel but you should be able to keep it going by pumping the fuel line bulb.
The O rings in the connectors are replaceable.
 
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