Sounds like Yanmar copied the old Ford design: Solenoids that were coinsumable parts and needed replacement regularly. If you have an external solenoid, that's easy, you can jump it directly to test/eliminate it as the problem.
"Pushed the button, no click, no whir" usually means no power to the starter solenoid or the starter itself. Clicks mean the solenoid is working but the starter is either getting no power, or is frozen. (Or sometimes the solenoid throw-out is frozen in the starter, from road dirt and congealed grease--unlikely in a boat.)
If your starter solenoid is external, and located someplace where it gets heat-soaked, you might consider relocating it to a cooler location, or arranging some ventilation on it. It is easy to test a solenoid with a multimeter, you apply power to the relay terminals, and see if it clicks and conducts across the power terminals. No click? Replacement time.
FWIW, no-name parts and counterfeit parts are a problem worldwide with things like external solenoids.