1987 F9.9 4-Stroke Carb problem

[MJH]

I have enjoyed reading the many misc. posts about the 4-stroke carb & don't feel as much like an idiot 'cause I can't get mine to run right. I have rebuilt the carb & now am focusing on the bi metal valves. It never ran right at start & idle with out "thumb choking" the intake. Now after rebuilding jets it seems to start & idle great- problem is at high speed it bogs down, seems to run too rich (sooty plugs). Since their is no high speed adustment it seems like the air flow is causing the richness. Will the replacing of the secondary bi-metal valve & air valve mounted on case (with A and C hoses) fix my problem? (anxiously awaiting parts from boats.net) Any info would be greatly appreciated!
MJH-Austin Texas

[boats.net]

It may be overchoking, check the choke plunger for sticking, if you pull up on plunger and engine runs better then it may still be a carb choke problem.

[MJH]

The plunger into the auto starter seems to drop after the engine warms up-normally. I will try to manipulte it to force it either up or down. it seems to have a little sliding clip for such a task. That is the one part I have not ordered yet from boats.net 'cause it seems to be working. I'll try anything.. Have not yet received my other bi metal valves and air valve ( conected to A & C hoses) Thanks for the advice I'll keep you posted with results

[MJH]

I was able to install the secondary bi metal valve ande the air valve on the cylindar housing. The motor seems to run abit smoother at lower RPMS but still only gets to 1/2 throttle before "bogging" out and over choking. Either due to too much gas or not enough air. This is one funky carb with all the air hoses & negitive pressure bi metal valve and carb body & jets with tiny little holes that go who knows where. It aint no Briggs & Stratton. Any help you can suggest to get a more solid & response on the upper end of the RPM range is appreciated. Can I install a smaller main jet orifice, or is the fact that I am using a high octane airplane fuel causing any problems. (It is almost Duck season)

[MJH]

After your advice and manipulating the choke plunger - it makes no difference on my top end bogging down. Can I install a smaller oriface main jet? It has a new one I bought from you that is spec'ed for the motor. Still running too rich at full thottle- since it is a 4 stroke I cannot adjust the fuel mix. Please help with any parts number on different jet size & I'll order it.