Hi Al,
My T9.9 does all that. It's the design of these tiny carb jets that keep
fouling up.
I imagine the F15 is very similar.

Sherwin D.

Al wrote:

I am considering buying a Yamaha f15hp outboard motor. I just heard
that it vibrates a lot on idle, and that it is rather hard to start on
cold. Is this true? I would reconsider this purchase depending on your
feedback. Thanks a lot!
Al