300HP merc Varados snapping gearboxes

[Frosty]

Ferry 40ft,-- 4 x300 mercs Verado, open deck seats approx 40 people strapped in. 1600 liters fuel. 60 mile trip open sea.

cruise RPM 4400 RPM limiter set 6200.

Counter rotation gearboxes 4 now in 500 hours, warranty now out.

Reasons for failure unkown yet eys witness says gearbox housing cracked open.

I suggested cutting rev limiter to 4400 sychronise electric throttles and check electric gear selection.

I cant think of much else.