OT surging outboard

clint s

Member
A carb is a carb and any help would be good........

Would a sticky float needle cause surging under load. 2 stroke 20hp Johnson circa early 90's. Boat will start and idle fine and run fine just off idle . Under load it will run good for 20 to 30 seconds and then surge back and forth. If it sits for a few minutes back to the same, run fine under load for 20 or 30 and then surge again.
 


All seems good. Pump will pump gas when cranking. and checked fuel inlet screen.

I will add that yesterday when attempting to start in a trashcan the carb would not take any fuel at all. I took the carb off removed the bowl and the needle was stuck closed. I did not take the float, needle and seat out just worked it up and down and it seemed to be fine and move freely, put it back together and it started right up. I know I should have taken it apart.

FF to today and the above issue with surging, that's why I am guessing the needle is sticking.


Removed the carb and opened it up just now and although the needle moved up and down there seemed to be a little "catch" in the movement of the needle. I removed needle and seat and there was a tiny bit of junk under the seat. Cleaned it up and now the needle moves freely.

I will probably order a rebuild kit for the pump and the carb, but wanting to take the boat out tomorrow
If in fact a sticky needle can cause surging I will give it a try ???
 
(quoted from post at 19:49:07 10/13/13) Fuel supply problem ..check lines for leaks and the vent to see if it can get air


Checked the lines with the engine running and for obstructions yesterday. Checked the vent on the water today. Hopefully it is the needle
 
Go with that repair first it is certainly wrong. Reclamp all fuel line connections, or pressure test them from the tank. A neighbor had a fuel tank that had the bottom of the suction tube break off and it would run out of fuel with 1/2 tank. Jim
 
If the needle were sticking, the engine would quit.

What you have is a partially blocked fuel jet somewhere.

We had the same problem with a friend's Honda generator. Turned out that the idle jet was completely plugged.
 
(quoted from post at 19:11:16 10/14/13) Clint
Does the needle valve have the rubber tip?
If it does,is the little spring keeper wire
hooked to the float?
Good Luck.

Steve A W

Yes and yes.
 
(quoted from post at 05:08:35 10/15/13) If the needle were sticking, the engine would quit.

What you have is a partially blocked fuel jet somewhere.

We had the same problem with a friend's Honda generator. Turned out that the idle jet was completely plugged.

The catch in the needle was part way meaning I think it would open partially, but not fully. Starving it for fuel at full throttle, but letting enough through at idle.
I hear what your saying though as there was a little gunk under the seat. The thing needs a good cleaning and all the lines replaced as well as both quick connect ends.
 
Ended up taking a friends boat out yesterday so do not know if it is fixed or not, with winter approaching I may not know until spring
 
(quoted from post at 14:26:11 10/15/13) Ended up taking a friends boat out yesterday so do not know if it is fixed or not, with winter approaching I may not know until spring

Lets get some closure to this. I had the boat out today and it ran good without a hitch. No surging. Thanks for everyone's help, I think it was a sticky needle and cleaning it did the trick. Caught one pretty big smallmouth, 4 rock bass and a few big sunnies.

Thanks again Clint
 

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