90hp Merc - low speed screw

I have a 2005 2-stroke Mercury 90hp, and need to know the location of the low speed adjustment screw on the carb? A picture would be helpful. I am not a boat engine mechanic, but have a slight bogging situation when i'm easing into the throttle on my boat. It will bog slightly, but if you feather the throttle a bit and ease into it everything works fine. Mostly noticeable when loading the trailer, once you're on the bunks and you put a load on the motor to slide it up further, it will bog and cut off... unless you utilize this feathering of the throttle. Other than that, the engine runs flawless... Can someone help me out? Thanks in advance. hvychev77

Get on the Port side of the engine....traffic side, not curb side. and look at the carb from the side. There is only one adjustment screw and it's spring loaded brass with a knurled edge. on the mid and lower there are holes in the plastic linkage for you to make adjustments....when in idle.

Rule of thumb is to open them up equally, 1/16 of an inch at a time (flat blade screwdriver, blade width essentially) until you can get the hole shot without bogging....hole shot...from idle in F gear to firewalled throttle. Trim, hull, loading of the boat, prop pitch, tilt angle and engine condition all play a part in that hole shot....but if the problem is just the low speed is set too lean, you have your answer.

Low speed jet may affect the idle 675 +/- 50 RPM in the water, in F gear, boat moving...the knerled white nylon screw on the Timing linkage arm...timing sets idle, not fuel. Merc selected that speed as it's fast enough to keep the engine from dieing and slow enough to shift without crunching.

Wow! What a detailed explanation, thanks so much Texasmark! I've made a small adjustment on the motor last night, very easy to find. Hopefully this weekend i'll be able to do some lake tests and see if it improves...Thanks again, cheers everyone!

Just wanted to circle back here... i backed the screws back out about 1/4 turn, made a night & day difference on how the engine performed at lower RPM's. Pretty much completely took care of my issue. Again, much appreciated for the detailed reply to my thread. Cheers!! hvychev77

hvychev77 said:

Just wanted to circle back here... i backed the screws back out about 1/4 turn, made a night & day difference on how the engine performed at lower RPM's. Pretty much completely took care of my issue. Again, much appreciated for the detailed reply to my thread. Cheers!! hvychev77

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