Starter going bad?
 

Merc. 5.0L EFI. Eng. starts normally when cold. When warm after running the starter will engage, crank eng. for 1-2 sec's, disengage and wind down. If I keep bumping the start switch eventually it will crank long enough to start. Does this sound like a dead spot on the starter windings?

Operating in saltwater ? How old are the risers?

Freshwater boat. Risers are good. This is not a hydrolock. Battery is new.

Does your boat have the remote solenoid? I had a voltage drop at the remote solenoid that gave me fits. Turns out I f'd up the wiring but the voltage drop kept the starter from engaging. You could hook up a remote starter switch and see if the starter works properly after it gets hot. That would probably be enough to tell you if it's the starter or something upstream.

I'll do that. Thanks for the suggestion.

An iffy battery switch can cause issues as well. As said, check remote solenoid. Resistance can change with heat from high current draw when in use.

Corrosion inside the battery cables can be a thing, too.