David - looks like you are on the right path: seek the root cause of he failure first.
Sunchaser is correct: the small sponsons on a cat hull don't allow for lots of machinery space, and airflow is often the first casualty.
We have several hundred NL gensets in the Caribbean charter cat market, and with proper application (air, fuel, exhaust systems properly handled at installation) we rarely have casualties. I have seen many small sets like yours with 25,000 hrs on them, with only maintenance items being needed.
As well, I have seen applications where the engine room was over 150F (no ventilation, hot day and direct sun on the hull) and it gets hotter inside the soundshield.
I'm not going to say Taiyo ends never break, it's just not frequent.
First thing I would look at is the air inlet (gen end cooling and combustion air) at the rear of the soundshield. The next would be the air exhaust port on the LH side of the soundshield...if air cannot get in or out its a recipe for trouble.