2011 150 hp 2 cycle Optimax. Will start at fast revs (4000 rpm) but die at 1000 rpm’s.

[lmbr]

Recently purchased this boat. Mechanic I purchased it from said he had reworked the engine. I replaced a switch on the throttle lever & shift shaft that he said controls the low idle fuel supply. No luck. It will start at 4000 rpm and then when I reduce the throttle slowly it’s ok down to about 1000 - 1200 rpm then dies. Fuel filter looks like it has been in it for a while. Does this sound like a dirty fuel system? I took it to the lake right after I got it and it acted like this but I was finally able to get it to run but when I stopped it wouldn’t run very well at idle. I haven’t tried it in the lake since. Just using muffs.