T25la Stalling

[gentleben]

I have a 2012 T25LA hooked to a pontoon boat. It idles well and runs well, but if I increase throttle quickly from idle it wants to stall. What is happening? It is too new for the carb to need a rebuild.

[99yam40]

brand new motors have problems with bad gas , varnish, or just crud just like old motors.
Something is plugged up from sitting or stuff in fuel

[gentleben]

Thanks for the reply. I'll flush everything, put some ring free in, run it at WOT for a while and see what happens

[99yam40]

Running a sick motor to see if it gets better can harm the motor if running lean

[gentleben]

happy endings, hopefully

Since forums like to hear positive resolutions to problems that have been posted, here's mine. Yesterday the stalling on my T25LA got so bad it conked out in the middle of the lake (while idling) and wouldn't start again. Had to get towed in to my dock. Previously, I had replaced the water - gas separator (had no water in it), fuel filter Clean also), and put Yamaha Ring Free in the gas. Still left me stranded. I saw a post on this forum where someone had similar difficulties and pulled the pilot screw out, blasted the hole with carb cleaner, reset the screw to factory, and was good to go. So that's what I did. Found the location of the screw in an online diagram, pried the plug off, verified the factory setting (2 3/4 turns out), unscrewed it and blasted the hole. After putting it back in to factory setting, the boat ran smoothly at idle, but still hesitated when goosing the throttle in neutral. Backed the screw out another 1/2 turn, and the hesitation reduced greatly. Evidently the factory setting for the idle circuit was too lean, and as it gummed up it just got worse. We'll see wh.at happens next time I take it out. So far so good, and thanks to this forum for pointing me in the right direction.

[boscoe99]

Later four stroke Yams with carburetors run very lean to begin with. The passage ways are so small they are prone to becoming clogged with junk which only makes the situation worse.

Some folks have been known to up the idle jet, and maybe the main jet, a size of two which can really improve the driveability of the motor.

I can't recall if the T25 uses as accelerator pump but think that it does. Remove the intake air box so that you can look directly into the throat of the carburetor. See if there is a horizontal brass tube at the front of the carburetor inlet. If so, quickly open the throttle valve and see if fuel dribbles out of the back side of the tube. It should spray out. Your carburetor might need to be completely dismantled and ultrasonically cleaned.

The hole in the back of the accelerator tube is unbelievably small. I can only begin to imagine how that hole was put there in the first place.

[gentleben]

Thanks for the tip, Boscoe. I'll check that out. I have a fair amount of experience with 4-stroke motorcycle carbs, but none with outboards. Should work the same way. Are there aftermarket companies who sell jet kits for outboard carbs like there are for cycles?

[boscoe99]

Yes. At a fraction of the price that Yamaha charges. Here is but one

Jets R Us mikuni, keihin, hitachi, holley, jets and carb parts

[gentleben]

Thanks. I'll check it out