Ignition Timing

Hello, I have not posted here in a while but I have a question.A friend of mine reciently bought a used boat.All is well with it however (it is a ski boat) after it is run pulling skiers and shuts it off, it has a hard time restarting. Sounds like the timing is advanced. The engine is a 351 Ford with a 4 barrel carburator.Is the timing on this fixed or is it similar to automobile applications? The boat is in the mid 90.s (year) The water temperature reads around 160-+10. When setting timing is this done at idle or at a specific speed?Any help will be appriciated, Ken