2000 40hp 2 stroke concern

[Sea2aeS]

I use my boat every week atleast once. For the past month now every time when i go out and push the throttle forward to get onto plane the engine acts as if its stumbling for a few seconds and then clears up and she hops up on plane and runs fine. The rest of the day it doesnt do this, but every time out for the first time getting up it stumbles. Its predictable now as it does this everytime the same. I have been running west marines brand of marine 2 stroke outboard oil, would this cause it? plugs arent fouled a bit & oil is tcw3 certified. the engine is a prime-start model, requiring me to pre-mix my gas and oil 50-1 at the pump. I use a measuring device so the mixture is dead on at 50-1, im not using too much oil. i use sta-bil for protecting fuel everytime i fill up as well.

carburetor float issue?
jets clogged?
carburetor setting too rich?
primestart issue?
west marine oil = junk?

[99yam40]

You can try a new set of lugs just to see if it will help, but the carbs may need to be looked at and cleaned.

I finally found out someone had drilled out the main jets in my C40 causing it to drop cylinders when pushed hard, but it did it even when warmed up.
you May need to let it warn up a little more before taking off so that the prime start system has time to shut off the enrichment.

[bbrks54@netscape.net]

definitely clean the carbs

[Atchafalaya_man]

I had that problem on my 40, 2s. I opened the idle screw on each carb about 1/2 of a turn (with the engine running) and noting no difference in idle, I left them at that setting, and experienced an instant fix of the stumbling problem.

They were ok for the idle speed but a tad too lean in that moment where more fuel was needed at low speed.

If that doesn't help, turn them back to where they were.