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Yamaha 20 4 stroke outboard

R

randy friday

New member
I have a 2o hp 4stroke I am working on and acceleration is bad. It bogs down each time I try WOT. IF I go slowly it will get there but not quickly.
Idles fine but is hard to cold start motor. Usually 7 to 10 pulls to start then pops sputters a few moments then when warm it is ok but no quick throttle ever.
I have checked compression and can only get 95 each. still, no smoke and runs fine (when warm). Removed carburetor and cleaned out, then changed plugs.
There is a bit of improvement but still not where i think it should be. I have read on the web these motors were undersized on jets from the factory. Dont know if that is true or not but cant guess what to put in it to try. I have a fair amount of tools but cannot do much with the electronic side as far as testing but am not opposed to buying anything as I work on other outboards. any help would be appreciated.;;;how do I get better response on throttle??
 
johnnygjr said:
Try pumping primer bulb while she's running
Click to expand...
I did try squeezing bulb this morning but made no difference. 11 pulls to start.
It does run better since cleaning out carb and adjusting slop out of linkage but is still hard to start and coughs and wheezes.
Once it is up and warm it is not great but is acceptable. Starting should be better. any suggestions would be appreciated.
Is there a way to check timing or maybe a electronic cold start like bigger engines with pre-enrichment valves?
I cant seem to get there. thanks
 
I pulled on rope several times. I'm not sure how many are required but couldn't get it past 95. I agree it is low so maybe I had a leak. I will do it over when I get back to engine." IF" it is fuel starved, and "IF" the jets are undersized is there any recommendations for upsizing? As I noted it does run better but I think it is still lacking. Too hard to start and and hard cranking throttle gets delayed acceleration. Slow gradual works fine but sometimes quick deceleration cause engine to die. All seemingly pointing to fuel. Is there a spark advance that should be happening? I'm just lost at this point but my right arm is going popeye.
 
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