3.5 mercruiser mpi not starting in neutral
 

1-My 1999 5.7 merc Bravo MPI will not start afer it is warm with out
using the accelerator in neutral and giving it fuel. I was told it is
a mercruiser problem with vapor lock. This seem kind of strange with a
fuel injected system.
any ideas?
2- I just got my 100 hr. tune up and now I am getting excessive black
build up on the back of my bout after a day of cruising. To rich?
wrong spark plugs?
3- what can I use to get the black off the back of my bout it wont
just wash off with water like it use to.


Thanks guy for all your help
Rog