Thread: 9.9 Nissan

No adjustment on the float. Probably not your issue. First, yes there should be a O ring inside the round connector where it hooks to motor. If it is missing or damaged you could be sucking air around it causing your problem. Even though you got cleaner to go through the jets you might still have some clogging. I would check the connection first and make sure it is not leaking. You should be able to check by installing a with out holding it in place pump up the bulb as hard as you can then let sit and check for any fuel leaking around it. Once that is eliminated, put just a couple of gallons of gas in tank and dose it up real good with some SeaFoam. Then run it for a while in drum or on muffs. Nothing more than a idle. After about 15 min shut it down and let sit over night then run it again. Let sit then take back to the lake and run it and see if that dosn't help. You never want to rev one on the muffs cause it can run away and tear up motor, running one in drum at to much rpm can heat up the water and cause motor to over heat.

It sounds like it is running lean. Too much air or not enough fuel. Check your fuel filter. Check compression on both cylinders since you got it in this condition. The fuel pump is vacuum operated. Poor compression can mess with its proper operation. Make sure the check valves are sitting flat. If not, you can try to turn them over or just replace them. If cray's suggestion doesnt work, an air leak at any gasket, intake manifold, reed plate or crank seal can cause a lean condition. These areas should be bone dry. If you have an oily residue, it is sucking air. Take it apart clean it good and replace gaskets or reseal with a good engine sealant. Every manufacturer makes their own but they are all pretty much the same. If it is a crank seal you can normally get them out and replace without taking it apart if you are careful not to nick the shaft or seal well. I think this is the parts list for your engine if you need it. https://www.nissanoutboardparts.com/...2N21043-3).pdf

Thanks for the input. I will give the suggestions a try. My connector does not have an o-ring so I will replace it and see what happens.

There s a float adj but not for faint of heart.First check man for float height this is measured from the body to top of float when held in the float up position you bend the tang on the float valve to change height down makes it higher up to lower.