2006 f40tlr

[Sandan2015]

The motor ran fine with the exception of an occasional spit/mist. I think it would've been fine if I just changed the fuel. I decided To rebuild the carbs, change the plugs, fuel filter, fuel/water separator and the fuel pump. (I also bought a new top Cowling, generator cover, air box and new prop). Now it runs perfectly from idle up to wide open throttle except once I am at full throttle for about 40 seconds, it kicks down to 5000 RPM's from 6000 and started to surge. If I cut the throttle back to about 3000 RPM's, after about 10 seconds will be running normal and I can go back up to wide-open throttle (for 30-40 seconds). I tried running the boat with a new portable fuel tank and line... same symptom. Any suggestions please? Here is a link to the motor running up to malfunction. https://youtu.be/C6-3dyOBU5E

[rodbolt17]

sounds like your running the fuel bowls dry.
what shape is the fuel pump in?

[99yam40]

same thoughts I had, but he said he replaced the fuel pump.

fuel line air leak maybe on the motor side, since he tried with a different tank and line.
On board filter area maybe

[Sandan2015]

Yes, I changed the fuel pump. When I rebuilt the carbs, I used the Yamaha carb repair kit (gaskets, floats)... there does not appear to be a way to adjust the float levels. They are all plastic with no adjustable parts. Is this correct? They just go in as they are?

[99yam40]

Hook up a piece of clear tubing temperarally coming out of the fuel pump if you can and look for air bubbles in the system, to rule that out

[Sandan2015]

Thank you for your responses. My next plan of attack is to change all of the fuel line pipes/hoses and the carb plate, insulator and "O" rings. Does this make sense? Is there anywhere or anything else that can be causing this?

[panasonic]

I would do what 99yami40 suggested first and see if it sucking air from somewhere first.

This started after you rebuilt the carbs...correct?

[panasonic]

When you rebuilt the carbs did you put in new float needle valves as well? The floats are not adjustable....they are what they are...

[Sandan2015]

Yes I did change the needle valve. The kit had two big gaskets, float, needle valve and metal hook, O ring for fuel/oil mixture valve and spring boot. After the rebuild it started right up and runs great at all speeds except after at full throttle for about 40 seconds it starts to fault. Thank you!

[rodbolt17]

what you are describing is the engine is consuming fuel faster than the fuel pump can supply it.
your not describing a carb issue.
your describing a fuel delivery issue.

[Sandan2015]

Thank you, so if I changed the fuel pump and tested the motor with a new portable tank and line, what else can I check? None of the hoses seem to be cracked.

[Sandan2015]

Thanks everybody! So I brought it to a marina... he says it was a pinched hose going into the second carburetor. He charged me $900 for six hours of labor to determine this. Amazing that this guy can sleep at night. Well, I'm back on the water.

[99yam40]

pinched hose at the carb should have been seen. just my opinion

Did someone install none preformed Yamaha hoses at the carbs causing this?

[panasonic]

Thanks everybody! So I brought it to a marina... he says it was a pinched hose going into the second carburetor. He charged me $900 for six hours of labor to determine this. Amazing that this guy can sleep at night. Well, I'm back on the water.

As Charlie Brown would say "Good Grief"

[rodbolt17]

I sleep well when I have to work behind a backyardigan that did a self inflicted wound.
especially when they pull the trigger multiple times.
that line was not pinched when that motor left japan.