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carburator float height?

In a carb, fuel "wants to travel" from an area of high pressure (the bowl) to an area of lower pressure (through the jet(s) and down the throat because of air getting sucked through the intake). (simple explanation of what is happening).

Now while it's true that the amount of fuel getting (sucked) through the carb is dependent on the needle valve (connected to the float which allows fuel in to the carb bowl) AND the main jet (which attempts to meter the fuel to a degree that is being sucked out) it is also effected by the amount of fuel in the bowl - more OR less fuel in the bowl than it was designed to operate at (tuned) will result in a richer or leaner running engine because MORE or LESS fuel gets sucked through the jet because more or less is "available" (due to the change in the "designed" pressure balance between the air and the fuel).

So getting the float set as close to spec as you can will allow your motor to run "the way it was designed" and makes sure that it doesn't get oil starved (2 stroke) by running lean, or fouls up by running rich...
 
I see, now i'm having an issue with my motor running at full throttle, it runs good for 10 seconds consistently then slowly bogs down and does 1/4 of the speed it should be doing. Now i suspected the fuel pump was acting up so had it rebuilt by my local marine shop but the problem was still there, even when i pump the ball at full throttle thinking the pump is not doing its job it does nothing. Seems like at low speeds the bowl fills up like like normal and burns whatever is inside and cant receive anymore, is it maybe getting to much fuel? could it be flooding out the engine? I cleaned the carbs myself and replaced all the gaskets and needle valves. Is there something i may have missed or should have done??
 
Is it stuck in the hole? Have you tried different trim angles? Do not run the motor WOT on the muffs it must have a load on the prop possible high rev limit kicking in? HP and serial number of the motor?
 
Its a 1993 mercury outboard 90hp 3 cylinder oil injected serial# oc293377, the trim angle does not matter I've tried.. no matter what gets done for the better on that motor the problem seems consistent each time, the carburetors are the only thing that never really had any professional work done, mind I cleaned them myself with super tech carb cleaner blew compressed air through all the nooks and passages and re did the gaskets and replaced needles. I took a video of what it is doing can't seem to upload it on here..
 
I've done that also I've bypassed the gas tank with an external gas tank with fresh fuel changed prime ball and connection at motor, i wanna say ever since i did the carbs myself the problem has acted up..
 
How old is the thermostat and have you checked the poppet is clean and the spring in good condition. Make sure that all smells good and the impeller is good then put it in a barrel of water with saltaway in it and let it idle for 1/2 hour or so to flush out all the circuits good.
 
There is a temp senser next to the thermostat housing, turn the ignition on and short the wire going to the senser to a good ground on the engine the warning horn should sound.
 
You can tell by reading the plugs. If the plugs come out white powdery on the electrode insulator do not run at high rpms until you get the issue solved. Running lean will cook the pistons. The plugs should be a nice toasty brown on the insulators and all three should be the same. Monitor your oil usage as well if unsure the oil injector is working correct premix 50:1 until you get it sorted out. Fill the fuel tank with premix and top the oil tank off and put a mark on the oil tank. Run the fuel tank almost empty and top it off again and convert fuel used into fluid ounces. Measure the oil it takes to fill it to the mark and divide ounces of oil into ounces of fuel. If close to 50:1 your good to go.
 
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