94 9.9HP 2-stroke "surging at full throttle"

[mtkinzel]

Has been a great motor. Spring cleaning includes gear lube, water pump, prop service, new motor end fuel lines, new remote tank, new boat end fuel lines (w/ water separator), fuel filter, plugs, carb kit (for both), carb disassemble, soak, and compressed air cleaning, and new fuel pump kit. No issues last season. Spark test good, compression good.

Test drive results.........starts first pull, idles like a kitten, smooth all day long UNTIL 75% plus on throttle and it surges as though it has a fuel restriction. Priming hose ball has no impact when it acts up. It does not cut off. The only issue seems to be WOT (75% + on the throttle).

My guess is to tear the carbs back down and redo.........what say those with way more problem solving skills than me? Thanks for any advice.

[mtkinzel]

This issue is for my 94 25HP 2-stroke yami<u></u>........My 9.9 yami is fine after all service. Sorry for the mistake.

[mtkinzel]

Can anyone offer the pilot screw adjustment setting for both the carbs on this model? I do have a manual but it covers my 90HP yami but not my smaller two outboards. Could the pilot adjustment be the culprit here? Thanks again for any response.

[xpress spanky]

It shouldn't be because of the pilot adjustment because that is basicly for idle.Sounds like your starveing for fuel thou.I would recheck the carbs really good,and also fuel delivery to the motor.I think the adjustment for the pilots is 1 1/2 turns out if i'm not mistaken,but if it idles good that's not what your problem is.

[mtkinzel]

Thank you. I recleaned the carbs today and will test run next weekend. I have set the pilot screws at one and half out until I can identify the specs for this motor. Thanks again.

[dward51]

If the recleaning of the carbs did not help, take a look at the fuel delivery system.

Check the pickup for obstructions, and make sure the vent is not restricted. Might flow enough at lower speeds, but restrictions at upper end (max fuel need) cause it to fail to deliver needed volume.

If you have a portable tank and another fuel hose, I would try it as well. That way you can eliminate the on boat tank & pre-motor portion of the fuel delivery system (or confirm it if the problem goes away on the external tank & hose).