20hp johnson runs full speed only with choke all the way out

[DEERSLAYER2000]

I have a 1968 20 hp johnson that will idle and runs fine then you start to go full throttle and it cuts out. Then you pull the choke out and it runs good but not like it should HELP PLEASE

 

[JB]

Re: 20hp johnson runs full speed only with choke all the way out

Fuel problem, Deerslayer.<br /><br />Probably gummed up carb, but could be a failing fuel pump or restricted fuel supply.<br /><br />Good luck.

 

[DEERSLAYER2000]

Re: 20hp johnson runs full speed only with choke all the way out

hey JB I have a new hose and bubble, and cleaned the carb. It worked fine when i bought it, I was just going down the lake when it happened.

 

[BoatBuoy]

Re: 20hp johnson runs full speed only with choke all the way out

Are you sure you didn't pick up some water from the bottom of the tank?

 

[DEERSLAYER2000]

Re: 20hp johnson runs full speed only with choke all the way out

new plastic tank too

 

[McGR]

Re: 20hp johnson runs full speed only with choke all the way out

Check all your fuel hoses and connections. It sounds like one may have developed an air leak which would lean out the mixture, requiring you to run with the choke on.

 

[JB]

Re: 20hp johnson runs full speed only with choke all the way out

You are making a lot of extra aggravation for yourself, Slayer.<br /><br />Never assume that a new part is good.<br />Never assume that a carb cleaning was successful unless the engine runs good. It doesn't.<br />Never assume fuel pump is good unless the engine runs good. It doesn't.<br />Never assume that no air is getting into the fuel supply lines or that there is no restriction in the supply system.<br /><br />I'll bet you a case of single malt that your engine is not getting enough fuel or is getting too much air.<br /><br />Prime suspect: Carburetor high speed circuit.<br />Other suspects: Fuel pump weak, air leaking into the supply system, air leaking into the crankcase via a bad reed plate gasket or carb gasket.<br /><br />Long shot: Pinched or restricted fuel flow from the tank to the pump.<br /><br />Good luck, and let us know what you find.

 

[DEERSLAYER2000]

Re: 20hp johnson runs full speed only with choke all the way out

JB OK I put all new hoses,tank,filter and cleaned the carb and even soaked the houseing. So if I have an air leak in the new hoses i should have gas leaking too RIGHT! Thanks for the help

 

[REELSPORT]

Re: 20hp johnson runs full speed only with choke all the way out

If you have a air leak ing the gas lines you should be leaking fuel I think

 

[G DANE]

Re: 20hp johnson runs full speed only with choke all the way out

As the fuel pump sucks fuel from the tank, any leak between tank pickup and fuel pump will not neccesary leak fuel, but draw air in by the vacuum. Please listen to the suggestions we make to you or we will not be able to be of any help. <br /><br />I think I would recheck the high speed jet in the bottum of the carb bowl, and the fuel pump diaphrame first though.