Help sputtering engine

[Roger Decker]

hi I have a 2001 Yamaha LS2000. I failed to store it correctly last year and now one engine starts up fine but with any throttle at all it sputters and sometimes back fires. It started in the he water I’d turn it off then restart and it would go fine then interminably it would do it again. I changed out gas even put super unleaded in it. No help on the one engine. So I pulled the carbs rebuilt them, changed gas filters, plugs. Still the same. Just put on a universal fuel pump, nothing is fixing this. Anyone seen this before?
Thanks,
Roger

 

[Roger Decker]

Ohhh also there is no stalling problem, idles fine and at full throttle other than an occasional back fire stays running. Just sputters though with no power/thrust

 

[4x15mph]

- can you describe the extent of your carb rebuild?
- fuel, air, spark - I would continue to look at fuel. Are both of the fuel shut offs turned on? I made this mistake Once!!!
- are all pulse lines connected to the carb?
- you could swap carb racks to see if that fixes it. Pretty easy but it requires new gaskets

 

[Roger Decker]

Hi I did a full rebuild cost 100$ and I put it in a hot acid bath after it was like new. I think has something to do with fuel delivery or timing. I wonder if a high pressure fuel pump will solve it. The one I bought was low pressure. For timing I have no idea how to adjust this

 

[4x15mph]

- for the rebuild, did you replace the springs and do the pop off pressure testing yourself
- I would consider swapping carb racks if the other engine doesn’t have this issue. It will narrow down the problem
- there isn’t timing that you change
- does the impeller/shaft turn freely? Pull the spark plugs and make sure the impeller moves freely
- you may want to take the fuel pump out of the equation for now and maybe remove the fuel filter temporarily
- pre mix or oil injected?

 

[Gym]

The backfire concerns me. That usually indicates timing or a plug firing intermittently. I also would not have used super high test fuel. That is for high compression engines and may cause preignition. Are both engines backfiring or just one? If both I would consider a fuel type or contamination issue. If one engine an ignition issue. Is your oil mixing properly? Straight gas could be a big problem.

 

[Roger Decker]

- for the rebuild, did you replace the springs and do the pop off pressure testing yourself
- I would consider swapping carb racks if the other engine doesn’t have this issue. It will narrow down the problem
- there isn’t timing that you change
- does the impeller/shaft turn freely? Pull the spark plugs and make sure the impeller moves freely
- you may want to take the fuel pump out of the equation for now and maybe remove the fuel filter temporarily
- pre mix or oil injected?

I did replace springs . I will check the impeller also hesitant to switch carbs right now. I want to try and switch the fuel lines in. In the gas tank there is a box that gets submerged and the gas is drawn through those lines. I pulled this, didn’t see any issues. But couldn’t check the lines. Maybe one is obstructed or damaged and pulling air?

 

[Roger Decker]

One engine is fine. The oil / gas is not pre mix and oil is flowing to all 3 carbs

 

[Roger Decker]

Is there anyway to fix ignition or check it other than buying new?

 

[bumpy]

Any chance there is water in the gas? In my old Four Winns, bad gas caused similar symptoms. Have you tried running from a known fresh separate gas tank?

EDIT: Sorry, bad gas would affect both engines.

 

[Roger Decker]

That’s not a bad idea though. I will try it. The other engine had a phase of same issue but worked through it

 

[4x15mph]

Oh - if other engine has had similar issues that changes some. Definitely use fresh gas if possible. Ignitions switches do go bad but I don’t think that would cause the sputtering

Are they both new fuel filters? Installed in the correct direction?

 

[Roger Decker]

Yeah correct direction. I will try the gas trick thanks!

 

[Roger Decker]

I figured it out maybe this will help others. Bringing of the summer I power washed the boat inside and out and I included the instrument panel. The fan switch area was corrupted (wet inside). It consisted of a connector with about 8 wires. One of which apparently was messing with the motor. When I disconnected the plug and both engines immediately ran perfect. Anyone know about this plug? If the reconnect the same issue is right back. The wires in that area are still wet too.
Roger

 

[Gym]

Blow the switch & wires off with compressed air to remove as much moisture as possible. Then spray with an electrical drying agent like silicone.

 

[Roger Decker]

Blow the switch & wires off with compressed air to remove as much moisture as possible. Then spray with an electrical drying agent like silicone.

Great suggestion. Thanks!