1972 johnson 25hp carb adjustment?

[loganmallory]

hello. just got this motor this spring. ran it first time in the river today. 35:1 oil, new lines, clean tank, guy said it just had a tune-up including carb rebuild, i put in new j6c .030. took about 30 pulls to start, and i finally had to put it in gear and advance throttle to start. ran excellent at high rpm, but really bad at low. ran for about 30mins total (all at high). removed cover, turned out high-speed adjust 1.5 turns (the one on top), and it ran AWESOME low speed (ie trolling!), BUT, no acceleration, and kind of crappy at high speed. there is a knob on the motor for low-speed adjust, but i think it has been disconnected. i assume it was supposed to go into the bottom of the front of the carb, but there is just a slot screw there now (maybe it is supposed to be there?). any clues or advice would be awesome. also, when running in gear, lots of water comes out of the spout, but also 2 fast streams come out of the FRONT of the shaft on the opposite side of the exhaust spout and just below through the 2 holes. is this normal? thanks.<br /> tim (logan&mallory are my kids)

 

[alcan]

Re: 1972 johnson 25hp carb adjustment?

Hi Logon<br /> The carb on your motor only has one adjustable needle valve. The one at the top of the carb. This is your low speed circut. Proper setting starts at 11\2 turns out from litely seated. The screw in the bottom on the bowl is a drain and access to your fixed high speed orfice. The recomended fuel\oil ratio is 50:1. Sounds like you might need to remove the carb for a cleaning. Hope this helps.

 

[seajay]

Re: 1972 johnson 25hp carb adjustment?

If this is a tiller drive the black knob is for a slow speed trolling. and is adjustable only when motor is warm.Agree with previous post there is only one adjustment on carb be sure not to screw in to tight as you will damage idle needle.

 

[loganmallory]

Re: 1972 johnson 25hp carb adjustment?

hi. i pulled the carb and did a complete re-build. it was not dirty, but i figured why not. i also put in new plugs and changed mixture to 50:1. it ran a little better. the low speed adjust needle worked best at about .75 turns out. still bogs at acceleration and deceleration. also, after running only 20 mins both plugs were quite fouled. any advice? thanks.<br /> tim

 

[alcan]

Re: 1972 johnson 25hp carb adjustment?

Hi Logon<br />It sounds like your motor is running too rich. Check float level and adjust. The float must be paralell to the carb body when inverted. Also check your main nozzle gasket. Beteen main nozzle and bowl. Once you get the high speed air\fuel mix correct, readjust the slow speed. 1.5 turns is just the starting point. You go from there until you get best perfromance. If you dont have correct fuel level in the bowl or a leaky-missing gasket, the slow speed wont be correct ether.

 

[johnevinrude]

Re: 1972 johnson 25hp carb adjustment?

clean out your gas tank, check the screen in the tank, and put in new gas.