20 hp johnson wide open throttle surging

[mbc2005]

hey, i have a late sixties johnson 20 hp. i have recently put some more money into it trying to repair and bring it back to sea worthy condition. i just rebuilt the carb and it runs pretty good, im happy at least. i have run it six different fishing trips since the rebuild. the past two times it has started surging at wide open throttle. to me i think its not getting enough spark for the fuel. i know absolutly nothing about points and condensor set ups. way before my time. i put two new plugs in it today and am going to run it in the morning. was wondering if anyone has experienced this? also how do you know if your water pump is good, bad, going bad....?

 

[mbc2005]

Re: 20 hp johnson wide open throttle surging

well i got the points on and set. took it out same thing. except this time i ran it with the cover off and seen the carb running out of gas when it was surging. anything?

 

[AEROCOOK]

Re: 20 hp johnson wide open throttle surging

well i got the points on and set. took it out same thing. except this time i ran it with the cover off and seen the carb running out of gas when it was surging. anything?

Float setting?
Fuel Pump? Try squeezing the primer bulb at WOT and see if the surging goes away.
If you dont know when the water pump impellor was last replaced you need to do it now, its an inexpensive part that is easy to replace.

 

[samo_ott]

Re: 20 hp johnson wide open throttle surging

How do you 'see' the carb running out of fuel? and as aerocook said, try pumping the bulb to see if it fixes it. You might have a weak fuel pump that cant supply enough fuel at WOT.

As for the water pump, you should see water/exhaust spray coming out about halfway down the rear leg. This spray should be cool at idle and quite warm at WOT. Also, feel the head at idle, it should be easy to touch. After a WOT run it should be quite warm to the touch but not sizzling hot. Water drops should not sizzle off if splashed on.