2008 F250 Starter or electrical issue.

[Skeeter61]

When you first crank up starter works fine.After you stop at a few spots when you come to start it will strain to turn over.Then you can stop it quickly after and its normal.It does this periodically.Brought boat to a yamaha shop they changed the positive wire from front helm to back lugs and it still doing it.

[Bluefish]

Have you checked your plugs to see if one looks clean, just a thought maybe getting hydro locked?

[99yam40]

start relay might have burnt contacts inside, not making good contact all of the time. common problem.

voltage drop test at different points of the circuit when the problem happens should lead you to where the problem is