Since I received some nice replies about my 4-stroke starting problem, I feel people
should know what the outcome was. I was fortunate to find an excellent mechanic just
one block from where my boat was tied up. He encouraged me to remove the
carburetor and bring it to him. I was nervous about doing it by leaning out over the
water, but it all went smoothly, except I had to improvise tools, because there was a
need to use open ended wrenches, which I didn't have, and used a combination of other
tools instead. I ran the carburetor over to the mechanic, who saw ominous signs of
residual fuel at the bottom of the float chamber. These were cleaned with
solvent and a high pressure air hose. Next came the two jets, low and high speed.
They were completely opaque, which he fixed by poking an appropriate wire through them
to open them up. The low speed was so fine that he had to improvise
by taking a strand of wire from some multi-strand electrical wire. He showed me
where the drain screw location and advised me to open it up for draining, whenever I
planned to not be using the engine. He thought that even letting it sit there for more
than a week could cause problems. On the Yamaha 9.9, the screw is easily accessible,
after opening the cover, so I will take the extra minute or so, to empty the
float chambers whenever I think I'll be away from the boat for an extended period.
He mentioned the low speed jet being extremely fine to give good fuel economy, but
leaving it open to clogging problems. In my case, the wider high speed jet was also
clogged, but I think this happens less often that the low speed jet. He wasn't big on
fogging carburetors, or on products like Stabil. He seemed to feel they get into the
float chambers but not necessarily the jets. Some genius will come up with a cure for
this problem. He just returned from one weeks vacation and had 5 outboards waiting
for him with carburetor problems (not sure if they were all 4-stroke). This
seems to be one of those problems the manufacturers don't want to address. The
Yamaha manual does not even list this kind of problem for engines that won't start,
but only lists clogged carburetor for bad engine idling. Of course, their cure for this
is taking the engine to a Yamaha dealer for service.

In any case, I got the carburetor back on the engine and for now, it's running fine.
Bottom line, running the gas out of the engine and fogging it does not guarantee that
you won't have problems at some future time. Draining the carburetor might help.

Sherwin D.