20 hp 1993 johnson will not run wot

[CTB60]

I'm helping my son with his 20 hp johnson that will idle fine but will not take throttle it spits and sputters unless you open the primer some. We changed power head lower gaskets and crank seal. Still no luck. Pulled the carb apart and cleaned no luck. What is next to try? We had it to the marina and they gave up seems they don't like working on old engines.

 

[oldboat1]

What model number is the motor?

 

[flyingscott]

Take the carb off and completely disassemble and soak it.

 

[w2much]

Compression test first. Did you soak the carb? and blow air through every passage? and remove each orifice or jet ? Float height adjustment, new needle and seat? Link and sync ? While the carb is off and the bowl is full of fuel blow compressed air through the throat from the front. Is there plenty of fuel air mixture coming out the back side. Did you put the cigarette out before doing this.I hope so.Are your throttle plates opening? Fuel supply to the engine, ? Fuel supply to the carb ?

 

[CTB60]

model number is J20CRETS, the carb was cleaned and every passage is open. The marina supposedly rebuilt the carb. with throttle open all the way if you put a hand over the carb opening quickly on and off the motor will rev as it should for a minuet or so. If the primer plunger is puled out slightly it runs as it should at open throttle but will not idle.Compression is 95 in both cylinders.

 

[w2much]

Spray starter fluid or better wd40 or perhaps something with a bit of lube in it all around the carb, the manifold and the primer hoses. I might second guess that rebuild. I might second guess them period.

 

[flyingscott]

Do another compression test 95 is low. The fact you pull the primer to get it to run right means that fuel is bypassing the carb.

 

[oldboat1]

^^Agree.

Try adjusting the idle mix on top (small increments when the engine is warm) : http://ww2.iboats.com/Carburetor-20/dm/cart_id.666986052--session_id.733065681--view_id.1537793 Make sure the nozzle (3) assembly is complete, and that the tube and orifice are in place and clean. The gasket underneath the nozzle also has to be in place.

 

[CTB60]

Son here. I did notice that there is a crack in #3 where the tube attaches to. I also replaced the tube because it did have holes in it. The nozzle assembly #3 is not available to purchase anymore. None on eBay.

 

[CTB60]

Do another compression test 95 is low. The fact you pull the primer to get it to run right means that fuel is bypassing the carb.

This motor is pull start no electric is 95 still low compression? could it be losing vacuum across piston rings?

 

[flyingscott]

Did you take both plugs out and pull until the gauge stopped moving (5 times)

 

[CTB60]

Yes both plugs removed and pulled over about 10 times. 95 PSI in each cylinder.

 

[oldboat1]

Son here. I did notice that there is a crack in #3 where the tube attaches to. I also replaced the tube because it did have holes in it. The nozzle assembly #3 is not available to purchase anymore. None on eBay.

The high speed jet shown in the diagram is in the nozzle. Use a small soft wire to clean the jet, followed by carb spray. Also insure there are no clogs in the nozzle. The crack you mention might be repaired with epoxy/super glue. A small engine shop might have a nipple that could be epoxied in place, if that is an issue.