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Irritating issue with Johnson Seahorse 20

J

Jet A-1

New member
I have a late 70's Johnson 20hp Seahorse. It's been in the family since new and has been well maintained (impeller, thermostat, plugs, gear oil etc. all replaced regularly in timely manner) and stored properly in the off season etc. However, for years it has had low speed issues. It starts first or second pull ALWAYS, but it runs rough during low speed operation, like it as a miss or something. Give it some throttle and it smooths right out and pulls like a train. So from about 1/2 throttle to wide open it runs as good as new. It idles decent, with a noticeable roughness, but it does idle. But as you give I some throttle from just off idle to about 1/2 throttle it stumbles. Above that it runs great! Any suggestions as to how I can fix this and get it running smoothly throughout the rev range?

Thx,

J
 
I would suggest getting carb n jets cleaned n maybe new carb kit if it hasn't been done in a while or if this has been done do what Kim suggested
 
I'll have to get back to you with the model number. I'm about 300 miles from the motor. Oddly, I have never had the carb off this engine, ever! As I said, it runs really well and always starts first or second pull, idles good and gets along a WOT just fine. It's the lower half of the rev range that needs attention. I guess it's time to do a little tuning. I've had the carbs on my ATV, dirt bikes, chainsaw, PWC, snow thrower, lawnmower etc. apart over the years but never the outboard. I recently picked up an old Edgewater Marlin (?) with a 1989 Johnson 225VRO that needs to be reassembled (overhauled powerhead needs to be reinstalled on an otherwise super clean looking unit with only freshwater use) so I imagine carb settings will be in my future quite a bit I'll follow up with how the 20 run once I get a chance to get back a it.

J
 
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