Yanmar starter relays

[GTI_16V]

Hello guys... I am working in a charter with 50 sailboats from 35-60 feet... And third time this season the starter motor burnt out on yanmar engine (don't know excatly model, 50 hp i think?)... It is third time on different boat, not the same... The problem is obviously well known, the starter relay doesn't dissengage, probabbly the contacts welds and can not dissengage... I made a few calls to authorized services and they all told me that the problem is with starter relay, and it is well known... We have a lot of boats with thoose same engines, and I am thinking what to do from prevent that happening... One thing crossed my mind, maybe add another relay and connect it to alternator so when alternator starts charging it will activate that relay which will cut power to starter? Or if anyone have some better idea, i would be greatfull... Maybe some kind of circuit to extend the life of the relay, or put different, more robust relay? The starter relay is this one
https://www.boatpartsandspares.co.uk...ter-2943-p.jpg